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Maraun, Douglas. "What can we learn from climate data? : Methods for fluctuation, time/scale and phase analysis." Phd thesis, [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981698980.
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Ouedraogo, Sylvain. "Dynamique spatio-temporelle des mouches des fruits (Diptera Tephritidae) en fonction des facteurs biotiques et abiotiques dans les vergers de manguiers de l'ouest du Burkina Faso." Thesis, Paris Est, 2011. http://www.theses.fr/2011PEST0096.
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Ravageurs de quarantaine, les mouches des fruits (Diptera : Tephritidae) constituent unecontrainte importante à l’exportation de la mangue au Burkina Faso. L’objectif de cette étudeétait d’améliorer nos connaissances sur l’écologie de ces ravageurs. Entre décembre 2007 etdécembre 2009, 1156598 Tephritidae ont été capturés dans 7 vergers présentant 8 cultivarsdifférents. Pendant cette période, l’évolution de la température, de l’hygrométrie et de lapluviométrie a été notée. 19764 mangues ont été collectées et observées afin de déterminerleur niveau d’infestation par ces insectes. Dix-huit espèces des genres Bactrocera, Ceratitis,et Dacus ont été identifiées, B. invadens et C. cosyra étant les plus abondantes. Les pics despopulations de mâles et de femelles, apparaissent entre mai et juin selon les sites. Les femelles,présentent aussi un pic en période de floraison des manguiers. Sept espèces de Tephritidaeinfestent les mangues et l’incidence moyenne de leurs dégâts varie entre 0% (Sabre) et 12,5%(Keitt), Keitt et Brooks sont les cultivars les plus infestés. 64% de ces dégâts sont causés parB. invadens et 31% par C. cosyra. L’inventaire des essences ligneuses autour de ces sites ainsique la collecte et l’incubation de leurs fruits entre avril 2008 et décembre 2009 ont aussi étéeffectués. 105 ligneux ont été recensés autour des vergers. Les fruits de 13 d’entre eux sontinfestés par 7 espèces de Tephritidae dont 6 se retrouvent aussi dans les mangues. Il s’agitsurtout de C. cosyra mais aussi de C. silvestrii, C. puntata et B. invadens.Ce travail montre les corrélations significativees entre les facteurs climatiques, la fluctuationdes populations, et les dégâts observés. Les espèces ligneuses alentours sont des refugespermettant le maintien des populations même hors saison de la mangue. Ces résultatsnouveaux permettent l’adaptation de la lutte contre ces ravageurs économiquement importantsau contexte agro-écologique de notre zone d’étudeClassified as a quarantine pest, mango fruit flies (Diptera Tephritidae) are an importantconstraint for mango exportation from Burkina Faso. The main objective of this study was theenhanced understanding of the ecology of mango’s Tephritids. 1156598 Tephritid flies weretraped from December 2007 to December 2009 in 7 mango orchards. During this monitoring,temperature, relative humidity and rainfalls were registered. 19764 mango fruits from 8cultivars were collected and obsreved during mango season in order to assess fruit fliesdamages. Eighteen Tephritids species notably from Bactrocera, Ceratitis and Dacus genuswere identified and B. invadens and C. cosyra are the dominant ones. The population peaks ofmales and females appear in the months of May & June according to the sites. The femalespresent a peak during the flowering period also of the mango trees. Seven species of mangoinfesting fruit flies have been identified and the incidence of this infestation varies between0% (Sabre) and 12.5% (Keitt). Keitt and Brooks are the most infested mango cultivars. 64 %of these damages are caused by B. invadens while 31 % by C. cosyra. The inventory of thewoody plants around these sites as well as the collection and the incubation of their fruitsbetween April 2008 and December 2009 were also carried out. 105 woody trees had beenlisted around the mango orchards. Out of which, the fruits of 13 trees were found infested by7 species of Tephritids, of which, 6 are also found in mangos. It is especially C. cosyra butalso C. silvestrii, C. puntata and B. invadens.This work shows significant correlations between Tephiritids population fluctuations, climaticfactors and mango damages. The woody species around mango tree orchards shelter thesepests even after mango season. These new results allow the adaptation of the mango fruit fliescontrol methods in the particular agro-ecological area of our study zone
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Petrakis, Roy, Leeuwen Willem van, Miguel L. Villarreal, Paul Tashjian, Russo Regina Dello, and Christopher Scott. "Historical Analysis of Riparian Vegetation Change in Response to Shifting Management Objectives on the Middle Rio Grande." MDPI AG, 2017. http://hdl.handle.net/10150/625060.
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Riparian ecosystems are valuable to the ecological and human communities that depend on them. Over the past century, they have been subject to shifting management practices to maximize human use and ecosystem services, creating a complex relationship between water policy, management, and the natural ecosystem. This has necessitated research on the spatial and temporal dynamics of riparian vegetation change. The San Acacia Reach of the Middle Rio Grande has experienced multiple management and river flow fluctuations, resulting in threats to its riparian and aquatic ecosystems. This research uses remote sensing data, GIS, a review of management decisions, and an assessment of climate to both quantify how riparian vegetation has been altered over time and provide interpretations of the relationships between riparian change and shifting climate and management objectives. This research focused on four management phases from 1935 to 2014, each highlighting different management practices and climate-driven river patterns, providing unique opportunities to observe a direct relationship between river management, climate, and riparian response. Overall, we believe that management practices coupled with reduced surface river-flows with limited overbank flooding influenced the compositional and spatial patterns of vegetation, including possibly increasing non-native vegetation coverage. However, recent restoration efforts have begun to reduce non-native vegetation coverage.
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McEwen, Lindsey Jo. "River channel planform changes in upland Scotland : with specific reference to climate fluctuation and landuse changes over the last 250 years." Thesis, University of St Andrews, 1986. http://hdl.handle.net/10023/2957.
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Rates of river channel change in three contrasting Scottish upland environments have been studied within the context of Climatic fluctuation and landuse changes over the last 250 years. The object of the research was to assess the spatial and temporal variation in channel types, the main controls on channel pattern and the dominant modes of channel adjustment. This was undertaken in a hierarchic framework with sites being investigated at three spatial scales. At a macro-scale, the spatial and temporal variation in channel pattern was evaluated through a random sample of river channel segments for each study area, derived from the first and second editions of the 1:10,560 0.S. maps plus the 1:10,000 third edition. Each channel segment was classified within a map-based channel system typology, specifically constructed for upland Scotland. Measures of activity collected for each sample incorporated sinuosity, braiding and lateral shift indices. Flood histories were reconstructed for each study area on the basis of discharge records, long rainfall records and contemporary accounts, to assess if there was any evidence for climatic change, fluctuation or periodicities. Estimates of the recurrence interval of rainfall and runoff events of differing magnitude, frequency and duration were assessed. Data, mainly of a qualitative nature, were derived from contemporary sources and estate plans to evaluate whether any landuse changes could have changed the runoff regime and sediment mobility within each catchment. At a meso-scale, 7 to 9 channel segments (already identified as "active" within the macro-scale study) were subject to a more detailed process-response analysis, using sequential aerial photographs. Finally at a micro-scale, the unit stream powers at these sites were studied in relation to specific runoff rates thereby relating channel process to channel form. The strength of the controls on channel planform type varied in degree with the area studied. The glacial legacy, the positioning of local baselevels and sediment size were found to be dominant controls. In terms of channel dynamics, the position of the Channel planform in relation to process thresholds and the existence of a quasi-equilibrium condition were both very important. In terms of process-response, the following general observations hold true. An extreme event of high RI (>100 years) will have a major disruptive impact if there is room for expansion of the channel system and providing thresholds for sediment transport are exceeded. If these thresholds are high, the fact that the channel has not recently been disrupted may also be important. The modes of expansion across the active area depend on the type of channel involved. Different study areas have different types of Channel pattern present and thus a greater likelihood of certain types of planform adjustment. The role of more moderate events (10-50 years) varies principally with sediment size and Channel slope. Small-scale modification may take place where stream powers associated with more moderate events exceed competence thresholds. It was found that process rates were highly variable in both time and space and that present rates were not necessarily representative of the past 250 years. Even within this timespan, there have been periods of increased activity in response to increased discharges of moderate magnitude (eg. 1870s-1880s within the Dee study area) and random extreme magnitude floods (eg. between 1948-1956 in the Tweed study area). The impact of landuse change, especially in relation to sediment mobilisation (Dee and Spey study areas), and speed of runoff (Tweed study area) also appeared to be important.
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SILVA, José Rodrigo Santos. "Avaliação de autocorrelações e complexidade de séries temporais climáticas no Brasil." Universidade Federal Rural de Pernambuco, 2014. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/5009.
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The objective of this study was to uncloak the dynamic of climate of Brazil, seeking to measure the regularity and the long range autocorrelation of daily climate series of temperature of air (average, maximum, minimum, and temperature range), relative humidity of air average and wind speed average. The data were obtained by Instituto Nacional de Meteorologia (INMET), at 264 meteorological stations, in the period from January 1990 to December 2012. We use the Detrended Fluctuation Analysis to realize the estimation of the Hurst exponent, the Multiscale Sample Entropy to estimating the entropy of series and the Kriging to interpolate the estimates made. We observed that higher latitudes tend to attenuate the mean of temperatures of air maximum, minimum and average, but increase the variability of the same. This inversion of the magnitudes of the mean and standard deviation is also observed in the relative humidity of air. The means of the estimated Hurst exponents estimated for Brazil were 0.81, 0.79, 0.81, 0.77, 0.83 and 0.64, and the estimated Sample Entropy, 1.39, 1.78, 1.46, 1.41, 1.56 and 1.66, respectively for average, maximum and minimum temperatures of air, temperature range, relative humidity of air average and wind speed average. The values of the estimated Hurst exponents showed a positive correlation with latitude in the temperature variables studied. Such a correlation was not observed in other variables. This a correlation was not observed in other variables. The regularities of climate series in Brazil were medians. Spatially, the greatest changes occurred in estimates of entropies in the scale 1 to 2 of , in the Multiscale Sample Entropy. As from ≥2 the changes observed were more subtle. We observe the influence of the Equatorial Continental air mass in entropy of temperatures daily average and maximum of air. The climatic factor of altitude influenced with more frequently in the observed results, mainly on temperature variables. In some cases, the continentality and the air masses were also identified as important factors in characterizing the spatial distribution of estimates made.
O objetivo deste estudo foi desvendar a dinâmica climática do Brasil, buscando mensurar a regularidade e a autocorrelação de longo alcance em séries climáticas diárias de temperatura do ar (média, máxima, mínima, e amplitude térmica), umidade relativa média do ar e velocidade média diária do vento. Os dados foram obtidos pelo Instituto Nacional de Meteorologia, em 264 estações meteorológicas, no período de janeiro de 1990 a dezembro de 2012. Utilizamos o Detrended Fluctuation Analysis para realizar a estimativa do expoente de Hurst, o Multiscale Sample Entropy para as estimativas da entropia das séries e o Kriging para a interpolação das estimativas realizadas. Observamos que maiores latitudes tendem a atenuar as médias das temperaturas máxima, mínima e média do ar, porém aumentam a variabilidade das mesmas. Esta inversão entre as magnitudes da média e do desvio padrão também é observado na umidade relativa média do ar. As médias dos expoentes de Hurst estimados para todo o Brasil foram 0,81; 0,79; 0,81; 0,77; 0,83 e 0,64; e do Sample Entropy estimado, 1,39; 1,78; 1,46; 1,41; 1,56 e 1,66, respectivamente para séries diárias de temperatura média, máxima e mínima do ar, amplitude térmica do ar, umidade relativa média do ar e velocidade média do vento. Os valores do expoentes de Hurst estimados apresentaram uma correlação positiva com a latitude nas variáveis de temperatura do ar estudadas. Tal correlação não foi observada nas demais variáveis. As regularidades das séries climáticas no Brasil foram medianas. Espacialmente, as maiores alterações nas estimativas das entropias ocorreram na escala 1 para a 2 de , no Multiscale Sample Entropy. A partir de ≥2 as mudanças observadas foram mais sutis. Observamos influência da massa de ar Equatorial Continental na entropia das temperaturas do ar média e máxima diárias. O fator climático da altitude atuou com maior frequência sob os resultados observados, principalmente nas variáveis de temperatura. Em alguns casos, a continentalidade e as massas de ar também foram apontados como fatores importantes na caracterização da distribuição espacial das estimativas realizadas.
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Hajhouji, Youssef. "Modélisation hydrologique du bassin versant de l'oued Rheraya et sa contribution à la recharge de la nappe du Haouz (bassin du Tensift, Maroc)." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30257/document.
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La recharge de l'eau souterraine est un paramètre encore peu connu du bilan hydrologique. La connaissance des processus et l'estimation précise de la recharge de l'eau souterraine est une condition préalable à une gestion efficace et durable des eaux souterraines dans les régions arides et semi-arides. En plus la recharge de l'eau souterraine est considérée comme le paramètre le plus direct avec lequel le changement climatique peut affecter les ressources renouvelables des aquifères. Les présents travaux de thèse s'intéressent à la recharge de l'aquifère alluvial de la plaine du Haouz par les crues de l'oued Rheraya (rivière intermittente), qui descend des montagnes du Haut-Atlas et traverse la plaine du Haouz du sud vers le nord. Ces travaux ont deux objectifs principaux (i) d'abord simuler le régime hydrologique de l'oued Rheraya dont les crues sont à l'origine de la recharge de l'eau souterraine, et ensuite (ii) aborder la quantification de la recharge de l'eau souterraine du Haouz par ces crues dans la zone du piémont atlasique. La modélisation des débits de l'oued Rheraya dans le Haut-Atlas marocain (225 km², altitudes comprises entre 1030 m et 4165 m) est réalisée en prenant en compte la composante nivale. Pour cela, le modèle conceptuel global GR4J est appliqué sur la période 1989-2009 en y adjoignant le module CemaNeige qui simule la dynamique de la composante neigeuse de manière semi- distribuée. La fraction enneigée simulée se révèle corrélée avec celle extraite du produit neige MODIS durant la période 2000-2009 (R2 = 0,64). De plus, l'équivalent en eau de la neige simulé est cohérent avec celui mesuré par la station automatique au sommet de l'Oukaimeden durant la période 2004-2006 (R2 = 0,81). Enfin, nous obtenons une simulation des débits qui reproduit bien la très forte variabilité saisonnière et interannuelle. En conclusion, le régime hydrologique de l'oued Rheraya est pluvio-nival avec une distribution unimodale des débits dont le maximum en avril coïncide avec la fonte des neiges. L'étude de la recharge de l'eau souterraine est effectuée à travers l'analyse du suivi des fluctuations de l'eau souterraine sous le lit de l'oued Rheraya sur deux cycles hydrologiques 2014-2015 et 2015-2016.[...]Groundwater recharge is a little known parameter in the water balance. Knowledge of processes and accurate estimation of groundwater recharge is a prerequisite for effective and sustainable management of groundwater resources. In addition, groundwater recharge is considered the most direct parameter by which climate change affects the renewable groundwater resources. The present PhD thesis focuses on the recharge of the alluvial aquifer of the Haouz plain by the floods of the Rheraya wadi (intermittent river), which descends from the High-Atlas Mountains and crosses the southern plain towards the North. This work has two main objectives: (i) simulating the hydrological regime of the Rheraya River whose floods are at the origin of the groundwater recharge, and (ii) Quantifying the groundwater recharge by the floods of the Rheraya in the zone of the High-Atlas piedmont. The runoff modeling of the Rheraya wadi in the High-Atlas (225 km², elevations ranging between 1030 and 4165 m.a.s.l.) takes into account the snow component. For this purpose, the GR4J conceptual and global model was applied over the period 1989- 2009, coupled with the CemaNeige module for semi-distributed snow dynamics. The daily snow coverage simulated by CemaNeige is in good agreement with that extracted from the MODIS snow product in the period 2000-2009 (R² = 0,64). In addition, the simulated daily snow water equivalent is consistent with that measured at the weather station of Oukaimeden (2004-2006, R² = 0,81). Finally, the runoff simulation reproduces quite well the strong seasonal and inter-annual variability. In conclusion, the hydrological regime of the Rheraya wadi is pluvio-nival with an unimodal distribution whose maximum in April is linked with snowmelt. The study of groundwater recharge is carried out through the analysis of the monitoring of groundwater fluctuations in the streambed of the Rheraya wadi, over two hydrological cycles 2014-2015 and 2015-2016.[...]
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Iltis, Corentin. "Effets du réchauffement climatique sur la performance d’un ravageur des cultures et impact sur les relations tritrophiques." Thesis, Bourgogne Franche-Comté, 2019. http://www.theses.fr/2019UBFCK051.
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Le réchauffement climatique va avoir des répercussions profondes sur les organismes vivants, en particulier les ectothermes comme les insectes, dont la physiologie et le comportement sont intimement liés à la température de leur environnement. Cette thèse propose d’étudier, par voie expérimentale, les conséquences du réchauffement climatique sur la performance d’un ravageur majeur de la vigne en Europe, l’eudémis (Lobesia botrana), et les conséquences pour l’interaction entre ce phytophage et les niveaux trophiques associés, en particulier les ennemis naturels (parasitoïdes). Les travaux se focalisent sur trois facettes du réchauffement climatique : une augmentation de température moyenne, une altération de l’amplitude thermique journalière, et l’occurrence d’une vague de chaleur.Les résultats attestent d’un impact des températures sur les traits reliés à la performance larvaire (capacités de défense des chenilles contre les ennemis naturels) et sur la reproduction des adultes, ainsi que sur l’interaction entre ce ravageur et un parasitoïde oophage. Par ailleurs, une importante variabilité de réponses thermiques est observée entre traits et parfois entre facettes du changement climatique, laissant suggérer des conséquences complexes de ce dernier sur la dynamique des populations du ravageur. Ainsi, prédire la réponse d’une espèce au réchauffement climatique nécessite d’adopter une vision relativement intégrative de la biologie de cette espèce, ainsi que de la complexité des changements se produisant au niveau de l’environnement thermique de l’organismeGlobal warming poses a major challenge to living organisms, particularly for ectothermic animals like insects, whose physiology and behaviour are closely related with direct thermal surroundings. This thesis aims at experimentally investigating the impacts of climate change on the overall performance of a major grapevine pest, the European grapevine moth (Lobesia botrana), and the associated consequences for interactions involving this phytophagous insect and adjacent trophic levels, more specifically natural enemies (parasitoids). The experiments conducted focus on three facets of climate change: an increase in mean temperature, an alteration of daily thermal range, and the occurrence of heat waves as extreme thermal events.Results highlight an impact of temperatures on both life-history traits related with larval performance (defensive abilities of caterpillars) and adult reproductive success, with demonstrated repercussions for the interaction between this pest and an oophagous parasitoid. Furthermore, they reveal an important variability of thermal responses occurring among traits and even facets of climate change, thereby suggesting complex consequences of this phenomenon in terms of pest population dynamics. Hence, predicting a species response to climate change requires adopting an integrative perspective of the biology of the focal species while considering the complexity of changes occurring in insect direct thermal environment
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Roberts, Jonathan Henry. "Evolutionary response to fluctuating climate in the Quarternary." Thesis, Kingston University, 2001. http://eprints.kingston.ac.uk/20689/.
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Sheldon's "Plus Ça Change" hypothesis predicts that there is a tendency towards evolutionary stasis in response to long-term climatic fluctuations (i.e. during the Quaternary) and gradualism during phases of relative climatic stability. Published Plio-Pleistocene climatic proxy data are examined and used to subdivide previously published and newly collected evolutionary series into "unstable" and "stable" climate subsets. Tests on these data are conducted using two similar fractal-based methods that determine evolutionary modes as deviations from a null hypothesis of random walk. Both methods are critically examined and are found to produce robust results in most cases. The results reveal a wide range of evolutionary modes during both the Pliocene and Quaternary with no overall tendency towards increasing stasis during the Quaternary. However, a slight tendency towards less stasis is also exhibited in temperate/polar forms during the Quaternary. Examination of three newly collected evolutionary series is conducted: (l) Morphometric trends in the ostracod Limnocythere inopinata from a high-resolution African Holocene sequence (25 - 37 years/sample) reveal short-term (10[sup]1 years) correlation between morphology and Sr/Ca-inferred salinity, interpreted to represent non-genetic physiological response. Evolutionary mode analysis also reveals relaxation of stasis where Sr/Ca ratios are more widely fluctuating, although the overall trend is one of stasis. (2) Attempts at confirming stasis in a Pliocene to recent bivalve, Glycymeris glycymeris are unsuccessful due to the low-resolution nature of the data. It is proposed that such studies should not be over-emphasised in analyses concerned with summarising evolutionary patterns in the fossil record unless sampling resolution is greatly improved. (3) Morphometric trends in the Miocene to recent foraminifera Globigerina bulloides exhibit stasis throughout with no significant change in evolutionary mode during the Quaternary. Previous work on latitudinal diversity gradients has revealed that there are no significant differences between speciation rates in tropical and temperate clades. Also, evidence from studies on recent floral and faunal changes has shown that both tropical and temperate communities respond in similar ways to a globally averaged change in temperature. It is proposed that these latitudinal similarities can be transposed on a temporal scale, representative of the changes between Pliocene to Pleistocene conditions: therefore no significant change would be expected at the onset of Northern Hemisphere glaciation. The higher degree of disturbance encountered in colder regions may, however, have resulted in conditions that led to more evolutionary change during the Quaternary. The mechanisms underlying the latter response can be invoked by using genetic algorithm modelling: where simulations are run with a large-scale shift in the environmental target, population means are seen to shift further from the optimum. It is expected that in "real" populations, this would lead to evolutionary change (or migration) in order to avoid extinction in unfavourable conditions. Further studies, utilising improved genetic algorithm modelling, tied to further compilation and testing of evolutionary series is expected to provide further insights into the mechanisms underlying evolutionary processes.
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Pan, Wenwei. "Rectifying the long-term climate fluctuations in the Milankovitch bands." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/54990.
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Chang, Fong-Chiau. "On the seasonality of climate fluctuations over the contiguous United States /." Thesis, Connect to this title online; UW restricted, 1986. http://hdl.handle.net/1773/10040.
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Mackintosh, Andrew. "Glacier fluctuations and climatic change in Iceland." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/22442.
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This thesis aims to develop an understanding of the relationship between climate, topography and glacier fluctuations in Iceland. A mass balance/glacier flow model is applied to the Holocene fluctuations of Sólheimajökull, an outlet glacier in southern Iceland. The model is also used to predict the response of Sólheimajökull to future climatic warming. The findings provide insight into the spatial variability of glacier fluctuations in Iceland, and the dynamics of Holocene climatic changes in the North Atlantic. The results from the model suggest that the response of Icelandic glaciers to climatic change can be related to glacier area-altitude distribution. Outlet valley glaciers located in high precipitation areas descend to elevations of 0-100 m where air temperature is mild. Ablation occurs throughout the year and glacier mass balance has a large amplitude response to temperature variations. Furthermore, outlet valley glaciers experience dynamic length variations in response to climatic change. This is a geometric effect where small changes in ice cap volume result in significant fluctuations in glacier lengths. In contrast, wide ice cap lobes in central Iceland exhibit a different response to climatic change. Precipitation levels are lower and glaciers terminate at altitudes of 600-800 m. Ablation is restricted to the summer months, and glacier mass-balance has a lower amplitude response to temperature variations. In addition, ice cap lobes experience smaller dynamic length fluctuations in response to climatic change. This is because ice cap margins undergo small changes in extent to response to changes in glacier volume. Finally, where ice cap lobes terminate on sandur plains, further advance leads to glacier widening and an unsustainable increase in ablation. The numerical model is used to successfully reconstruct Holocene climatic changes over the last 5000 years from the record of glacier length variations in Sólheimajökull.
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Bradwell, Tom. "Glacier fluctuations, lichenometry and climatic change in Iceland." Thesis, University of Edinburgh, 2001. http://hdl.handle.net/1842/29959.
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This thesis examines the spatial and temporal expression of Holocene glacier fluctuations in southeast Iceland. The study uses geomorphological evidence to reconstruct the former extent of Lambatungnajökull -a non-surging, valley glacier flowing from the eastern flank of the Vatnajökull ice-cap. Lichenometry is used to date recent glacial landforms and decode the pattern of glacier fluctuations over the last 300 years. Tephrochronology is used to date older features (<10,000 yr). The results show a pattern of fluctuations driven by climatic change. During the Lateglacial-Early Holocene Period the glacier terminus was situated at the present-day coastline. The ice-margin has retreated c. 20 km during the last 10,000 years. At least four periods of glacier re-advance have been identified, at c. 5000,3000,1600 and 170 years BP. Overall, the cumulative ice recession since c. 10 ka BP represents an ELA rise of c. 400 m which equates to an increase in mean air temperature of at least 2°C, assuming constant precipitation levels. Since the late 181" century, Lambatungnajökull has been in overall retreat. Moraines dated using two different lichenometric techniques indicate that the most extensive period of glacier expansion during historical time culminated shortly before c. AD 1795, probably in the 1780s. Recession over the last 200 years has been interrupted by re-advances in the 1850s, 1870s, and c. AD 1890. In the 20`h century, most notably in the 1930s and 1940s, Lambatungnajökull receded more rapidly than at any time during the previous 150 years. However, brief cold spells (-5 yrs), centred around the years AD 1918 and AD 1964, temporarily halted glacier recession. Lambatungnajökull has only retreated slightly over the last 20 years. The degree and nature of glacier retreat since 1930 compares well with similar-sized glaciers in southern Iceland. Furthermore, the pattern of glacier fluctuations over the last 150 years reflects the temperature oscillations recorded at nearby meteorological stations. Much of the climatic variation experienced in southern Iceland, and the glacier fluctuations that result, can be explained by secular changes in the North Atlantic Oscillation. A shift to more zonal atmospheric circulation and a weaker Icelandic Low - resulting in a greater frequency of negative NAO anomalies - may have been responsible for the cooling and associated glacier advances of the 18`h and 190' centuries. One implication of this work relates to the exact timing of the Little Ice Age in the Northeast Atlantic. The advanced position of glaciers during the late 18`" century suggests that this period represented the culmination of the Little Ice Age in Iceland. This contrasts with the current consensus that the Little Ice Age 'glacier maximum' in southern Iceland was during the late 19`h century. Other implications concern lichen-dating and its wider applications. Firstly, this research shows that the 'growth' curve of yellow-green Rhizocarpon lichens over the last 270 years in southeast Iceland is not linear. Although growth rates appear constant for periods of several decades, the growth 'curve' is exponential overall, with larger (older) lichens apparently growing more slowly than smaller lichens. Secondly, growth rates of Rhizocarpon Section Rhizocarpon in Iceland vary as a function of climate, with growth in the moist, maritime, southeast being c. 40% faster than in the cooler and drier northwest. Thirdly, this growth rate relationship - across the Northeast Atlantic region as a whole - can best be expressed in terms of climatic 'oceanicity' (r2 = 0.95). This latter relationship could be used to estimate lichen growth rates in areas where dating curves cannot be constructed. Finally, these findings suggest that lichen growth rates are likely to have varied in response to climatic change. In Iceland, slow-growing lichens, such as Rhizocarpon, probably grow more rapidly now - since the climatic amelioration of the 1920s and 30s - than they did in the cooler and drier periods of the 18's and 19'" centuries
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Bilich, Richard Christian. "Climate Change and the Great Plague Pandemics of History: Causal Link between Global Climate Fluctuations and Yersinia Pestis Contagion?" ScholarWorks@UNO, 2007. http://scholarworks.uno.edu/td/632.
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The two great bubonic plague outbreaks of history, Justinian's Plague and the Black Death were responsible for the deaths of over one hundred million individuals across Eurasia and Africa. Both occurrences of the plague coincided with climatic shifts that are well documented by both literary and physical evidence. This thesis explores the possibility that both Justinian's Plague and the Black Death were precipitated by climatic shifts preceding their respective eras and that these changes also contributed to disappearance of each pandemic. A scientific analysis investigating the climatic changes including the anomalous weather of 535-536 A.D., the Medieval Warm Period, and the Little Ice Age are correlated with literary evidence recording the transmission and dormancy sequence of the plague. Although distinct differences exist between the origins of climate change in the periods preceding each plague, the effects of such changes clearly resulted in conditions ideal for the resulting pandemics.
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Bergner, Andreas G. N. "Lake-level fluctuations and Late Quaternary climate change in the Central Kenya Rift." Phd thesis, Universität Potsdam, 2003. http://opus.kobv.de/ubp/volltexte/2005/107/.
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Diese Arbeit beschäftigt sich mit der Rekonstruktion von Klima in historischen Zeiten im tropischen Ostafrika. Nach einer Übersicht über die heutigen klimatischen Bedingungen der Tropen und den Besonderheiten des ostafrikanischen Klimas, werden die Möglichkeiten der Klimarekonstruktion anhand von Seesedimenten diskutiert. Es zeigt sich, dass die hoch gelegenen Seen des Zentralen Keniarifts, als Teil des Ostafrikanischen Grabensystems, besonders geeignete Klimaarchive darstellen, da sie sensibel auf klimatische Veränderungen reagieren. Veränderungen der Seechemie, wie sie in den Sedimenten aufgezeichnet werden, eignen sich um die natürlichen Schwankungen in der Quartären Klimageschichte Ostafrikas nachzuzeichnen. Basierend auf der guten 40Ar/39Ar- und 14C-Datierbarkeit der Seesedimente wird eine Chronologie der paläoökologischen Bedingungen anhand von Diatomeenvergesellschaftungen restauriert. Dabei zeigen sich für die Seen Nakuru, Elmenteita und Naivasha kurzfristige Transgression/ Regressions-Zyklen im Intervall von ca. 11.000 Jahren während des letzten (ca. 12.000 bis 6.000 J.v.H.) und vorletzten Interglazials (ca. 140.000 bis 60.000 J.v.H.). Zusätzlich kann ein allgemeiner, langfristiger Trend der Seeentwicklung von großen Frischwasserseen hin zu stärker salinen Gewässern innerhalb der letzen 1 Mio. Jahre festgestellt werden. Mittels Transferfunktionen und einem hydro-klimatischen Modellansatz können die restaurierten limnologischen Bedingungen als klimatische Schwankungen des Einzugsgebietes interpretiert werden. Wenngleich auch der zusätzliche Einfluss von tektonischen Veränderungen auf das Seeeinzugsgebiet und das Gewicht veränderter Grundwasserströme abgewogen werden, zeigt sich, dass allein geringfügig erhöhte Niederschlagswerte von ca. 30±10 % zu dramatischen Seespiegelanstiegen im Zentralen Keniarift führen. Aufgrund der etablierten hydrrologisch-klimatischen Wechselwirkungen werden Rückschlüsse auf die natürliche Variabilität des ostafrikanischen Klimas gezogen. Zudem wird die Sensitivität der Keniarift-Seen in Bezug auf die Stärke der äquatorialen Insolation und hinsichtilch variabler Oberflächenwassertemperaturen des Indischen Ozeans bewertet.In this work, an approach of paleoclimate reconstruction for tropical East Africa is presented. After giving a short summary of modern climate conditions in the tropics and the East African climate peculiarity, the potential of reconstructing climate from paleolake sediments is discussed. As demonstrated, the hydrologic sensitivity of high-elevated closed-basin lakes in the Central Kenya Rift yields valuable guaranties for the establishment of long-term climate records. Temporal fluctuations of the limnological characteristics saved in the lake sediments are used to define variations in the Quaternary climate history. Based on diatom analyses in radiocarbon- and 40Ar/39Ar-dated sediments, a chronology of paleoecologic fluctuations is developed for the Central Kenya Rift -lakes Nakuru, Elmenteita and Naivasha. At least during the penultimate interglacial (around 140 to 60 kyr BP) and during the last interglacial (around 12 to 4 kyr BP), these lakes experienced several transgression-regression cycles on time intervals of about 11,000 years. Additionally, a long-term trend of lake evolution is found suggesting the general succession from deep freshwater lakes towards more saline waters during the last million years. Using ecologic transfer functions and a simple lake-balance model, the observed paleohydrologic fluctuations are linked to potential precipitation-evaporation changes in the lake basins. Though also tectonic influences on the drainage pattern and the effect of varied seepage are investigated, it can be shown that already a small increase in precipitation of about 30±10 % may have affected the hydrologic budget of the intra-rift lakes within the reconstructed range. The findings of this study help to assess the natural climate variability of East Africa. They furthermore reflect the sensitivity of the Central Kenya Rift -lakes to fluctuations of large-scale climate parameters, such as solar radiation and sea-surface temperatures of the Indian Ocean.
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Dugmore, Andrew J. "Holocene glacier fluctuations around Eyjafjallajökull, south Iceland : a tephrochronological study." Thesis, University of Aberdeen, 1987. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=166196.
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Stratigraphic studies of layers of volcanic ash, or tephra, in buried soils have been used to date accurately Holocene glacier fluctuations in Southern Iceland. 132 stratigraphic sections up to 11m deep, and containing up to 78 tephra layers, were logged to a resolution of 0.25cm. The chronological framework was completed with 12 radiocarbon dates, and by examing the association of the tephra stratigraphy with moraines representing former ice margins, a chronology of Holocene glacier fluctuations was constructed. The forelands of five glaciers were studied: Seljavallajokull, Gigjokull and Steinholtsjokull (outlets of Eyjafjallajokull) and Solheimajokull and Klifurarjokull (outlets of Myrdalsjokull). This study has shown for the first time that large glaciers existed in mid-Holocene Iceland because after 700 BP and before 4500 BP Solheimajokull extended at least 4km beyond its present limits, and terminated at less than 100m above sea level. Other major advances of this glacier culminated before 3100 BP, and between 1400-1200 BP. In the tenth century AD Solheimajokull was also longer than during the late Little Ice Age (1700-1900 AD). In contrast, Klifurarjokull and all the outlets of Eyjafjallajokull reached a maximum Holocene extent during the late Little Ice Age. It is proposed that the anomalous behaviour of Solheimajokull may be explained as a result of catchment changes caused by the growth of the Myrdalsjokull ice cap. The great human impact on the landscape since the Norse Settlement (c870-930 AD) has also been assessed as a result of the extensive study of the aeolian sediments lying between numerous, accurately dated tephra layers. These studies show that a zone of chronic soil erosion developed in the natural upland pastures immediately after the Norse Settlement and slowly swept down hill to reach lowlying areas during the last 400 years.
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Ceballos, Lina Isabel. "North pacific gyre oscillation synchronizes climate fluctuations in the eastern and western boundary systems." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26552.
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Thesis (M. S.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2009.Committee Chair: Di Lorenzo, Emanuele; Committee Member: Bracco, Annalisa; Committee Member: Webster, Peter J.. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Deschenes, Olivier, and Michael Greenstone. "The Economic Impacts of Climate Change: Evidence from Agricultural Profits and Random Fluctuations of Weather." MIT Joint Program on the Science and Policy of Global Change, 2006. http://hdl.handle.net/1721.1/31205.
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This paper measures the economic impact of climate change on agricultural land in the United States by estimating the effect of the presumably random year-to-year variation in temperature and precipitation on agricultural profits. Using long-run climate change predictions from the Hadley 2 Model, the preferred estimates indicate that climate change will lead to a $1.1 billion (2002$) or 3.4% increase in annual profits. The 95% confidence interval ranges from –$1.8 billion to $4.0 billion and the impact is robust to a wide variety of specification checks, so large negative or positive effects are unlikely. There is considerable heterogeneity in the effect across the country with California’s predicted impact equal to –$2.4 billion (or nearly 50% of state agricultural profits). Further, the analysis indicates that the predicted increases in temperature and precipitation will have virtually no effect on yields among the most important crops. These crop yield findings suggest that the small effect on profits is not due to short-run price increases. The paper also implements the hedonic approach that is predominant in the previous literature. We conclude that this approach may be unreliable, because it produces estimates of the effect of climate change that are very sensitive to seemingly minor decisions about the appropriate control variables, sample and weighting. Overall, the findings contradict the popular view that climate change will have substantial negative welfare consequences for the US agricultural sector.Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/).
Greenstone acknowledges generous funding from the American Bar Foundation.
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Mewis, Heike. "Ecological stability of Indo-Pacific coral reefs during Quaternary climatic fluctuations." Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17456.
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Rezente Korallenriffe sind einer ganzen Reihe von Bedrohungen ausgesetzt. Das Pleistozän bietet die Gelegenheit Veränderungen an Korallenriffgemeinschaften durch Klimaschwankungen hinweg zu studieren und mit heutigen Riffen zu vergleichen. Am besten sind pleistozäne Riffe in der Karibik untersucht, während aus dem Indo-Pazifik, der über eine deutlich höhere Biodiversität verfügt, bisher nur wenige quantitative Studien vorliegen. Frühere Studien zeigen eine erstaunliche Stabilität und Langlebigkeit der Korallengemeinschaften hinsichtlich Diversität und taxonomischer Zusammensetzung trotz extremer Meeresspiegelschwankungen und starker klimatischer Veränderungen im Quartär. Die vorliegende Arbeit behandelt zwei Regionen, aus der quantitative Daten auf Artniveau über die Zusammensetzung der fossilen Korallengemeinschaften bisher weitestgehend fehlten: das tropische Vanuatu (Südpazifik) und der subtropische Sinai, Ägypten (nördliches Rotes Meer). In Vanuatu sind mindestens 5 fossile Riffterrassen mit einem Alter von etwa 5000 - 400.000 Jahren überliefert, von denen 4 detailliert untersucht werden konnten. Veränderungen in der Diversität wurden sowohl lateral als auch vertikal nur mit unterschiedlichen Riffhabitaten in Verbindung gebracht. Die Riffe waren insgesamt über die Interglaziale bin ins mittlere Holozän hinweg stabil. Nur die Gattung Acropora scheint erst in den letzten 96.000 Jahren häufiger zu werden. In Ägypten wurden Daten aus der jüngsten interglazialen Terrasse (MIS 5e, ~125.000 Jahre) mit rezenten Daten aus dem Roten Meer verglichen und eine Migration von Arten nach Norden während des letzten Interglazials belegt. Diese Beobachtung unterstützt frühere Arbeiten, die eine Verschiebung der Riffdiversität in höhere Breiten verbunden mit einer Abnahme der Diversität in niederen Breiten aufzeigten, sowie Studien, die das nördliche Rote Meer als mögliches Refugium für Korallen im Zuge der weiteren Klimaerwärmung sehen.The Pleistocene provides the opportunity to study changes of coral reef communities through times of climate change, and to compare fossil to recent reefs. Whereas Pleistocene reefs from the Caribbean are well studied and understood, the much larger Indo-Pacific region with a greater coral diversity is represented by only a few quantitative studies on community ecology. Previous studies observed an astonishing persistence and stability in community composition and diversity throughout several interglacial episodes until today, which is contradictory to the claim that recent coral reefs are especially sensitive to climate change. The present study deals with two Indo-Pacific regions that so far lacked quantitative data of fossil reef communities: tropical Vanuatu (Coral Sea) and subtropical Sinai, Egypt (northern Red Sea). In Vanuatu at least seven fossil reef terraces with ages between 5,000 and 400,000 years are preserved, of which four could be studied in more detail. A great variability was observed among terraces and especially among sub-environments within terraces. Reefs remained stable in terms of diversity throughout the Pleistocene and Holocene but it seems that the dominance of the coral genus Acropora is a fairly recent phenomenon in Vanuatu, because this genus does not play a large role in terraces older than 96,000 years (MIS 5c). In Egypt quantitative and binary data from the last interglacial episode (MIS 5e) were compared with data from the recent Red Sea and adjacent regions. These show a northward migration of coral taxa during the last MIS5e. This observation confirms earlier studies that demonstrated a range expansion of tropical reef communities towards higher latitudes, and supports studies that suggest the northern Red Sea and especially the Gulf of Aqaba as future refuge for corals during climate warming. These results indicate that coral reefs were able to cope with dramatic environmental changes in the absence of anthropogenic impact.
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García, Juan Luis. "Late-Pleistocene Glacial and Climate Fluctuations in the Torres del Paine Region (51ºS), Southern South America." Fogler Library, University of Maine, 2011. http://www.library.umaine.edu/theses/pdf/GarciaJL2011.pdf.
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Fall, Patricia Lynn. "Vegetation dynamics in the southern Rocky Mountains: Late Pleistocene and Holocene timberline fluctuations." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184610.
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Plant macrofossils and pollen from six small basins in western Colorado are used to trace the history of vegetation and climate over the last 15,000 years. The late-glacial upper timberline was 2800 m, and sparse krummholz Picea grew up to 3200 m. Summer temperatures were 3° to 5°C cooler than today. The late Pleistocene climate was influenced by winter storms from the Pacific. Precipitation shifted to a summer-dominated pattern by at least 9000 yr B.P. with the development of the summer monsoon. Plant fossils from bogs and lakes located near modern ecotones track the elevations of the temperature-controlled upper timberline and the moisture-controlled lower forest through the Holocene. Between 9000 and 4000 yr B.P., the Picea engelmannii-Abies lasiocarpa forest covered a broader elevational range, with upper timberline 200-300 m higher than today. Mean annual temperatures were 1.8°C warmer, and mean summer temperatures were 2.1°C warmer, than today. Temperatures were still about 1°C warmer prior to 2000 yr B.P. The lower limits of the montane and subalpine forests were 100-200 m below their modern elevations from 9000-4000 yr B.P. Mean annual precipitation was 50-100 mm greater. By 2600 yr B.P. the modern lower forest borders were established. Modern pollen dispersal, transportation, and deposition was sampled in atmospheric collectors, moss polsters, and surface lake sediments. Annual accumulation rates range between 1000 and 5000 grains cm⁻²yr⁻¹. Modern influx (grains cm⁻²yr⁻¹)averages: 1100 in alpine tundra, 2700 in the subalpine forest, 3400 in the montane forest, and 200 in shrub steppe. Pollen spectra in atmospheric traps and moss polsters reflect local vegetation, and provide effective modern analogs for pollen accumulation in peat bogs. In forested environments 80-90% of the pollen deposition in small lakes (< 5 ha) with no inflowing streams comes from atmospheric input. Pollen spectra in open vegetation are distorted by pollen from other vegetation types. At least half of the pollen deposition in small alpine lakes comes from taxa growing up to 1500 m lower in elevation.
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Viens, Robert J. "Late Holocene climate change and calving glacier fluctuations along the southwestern margin of the Stikine Icefield, Alaska /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/6737.
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Proust, Jean-Noël. "Expression sédimentologique et modélisation des fluctuations glaciaires : exemple des dépôts du Protérozoïque terminal au Mali occidental /." Strasbourg : Institut de géologie, 1993. http://catalogue.bnf.fr/ark:/12148/cb356968567.
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Gudmundsson, Hjalti Johannes. "Holocene glacier fluctuations and tephrochronology of the Öræfi district, Iceland." Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/15756.
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The aims of this thesis are to refine the tephrochronology of the Öræfi district, SE Iceland and assess the Holocene glacier fluctuations of the Öræfajökull ice cap. The pattern and timing of glacier fluctuations are determined using glacial geomorphology and tephrochronology, and the implications for palaeoclimate are assessed. Iceland is important to the study of global and regional climatic change because it is located close to both the marine and atmospheric Polar Fronts widely regarded as the key factors in the climate of the North Atlantic region. Six outlet glaciers were studied: Svinafellsjökull, Virkisjökull, Kotárjökull and Kviárjökull originating from the Öræfajökull ice cap and Skaftafellsjökull and Morsárjökull originating from the Vatnajökull ice cap. A long history of glacier fluctuations were found with a similar temporal pattern of glacier oscillation between the outlets of Vatnajökull and Öræfajökull. A maximum of eight advances have been identified. The oldest advance is inferred to date from the maximum of the last Glaciation ca. 18000 yrs BP. The first advance in the Holocene occurred ca. 9700 BP during a still-stand of the last Termination. The onset of the Neoglaciation occurred between 6000 BP and 4600 BP with an expansion of all of the studied glaciers. Subsequent smaller advances have been dated to ca. 3200 BP, ca. 1800 BP, ca. 700 BP, ca. 200 BP and ca. 80 BP. The most significant movement of the Polar front during the Holocene is likely to have occurred around 5000 BP, and, as a consequence, an estimated temperature cooling of ca. 2.5°C took place in Iceland, perhaps the greatest cooling since the last Termination. Within the broad pattern of change, glaciers in the study area show variability which represents local precipitation patterns, contrasting topography and change in glacier process. In this thesis a total of 22 silicic tephra layers are identified from over 90 profiles in the study area. The majority of these layers are dated to the latter part of the Holocene. Three silicic tephras were deposited during historical time (post 900 AD) namely, Vö ca. 900AD,HI104 and Ö1362. The Vö ca. 900 AD and the H1104 tephras are located for the first time. Specific prehistoric (pre 900 AD) tephras identified include Hekla-Ö, Hekla-4 and Hekla-S. The tephrochronology of the Öræfi district is also used to assess the eruption history of the Öræfajökull stratovolcano during the Holocene. Prehistoric eruptions are dated to ca. 9200 BP, ca. 6500 BP(?), ca. 4700 BP, ca. 2800 BP and ca. 1500 BP. Jökulhlaups accompanied the eruptions of 1727 AD, 1362 AD and ca. 1500 BP and are likely to have followed older eruptions of the volcano. A strong relationship occurs between volcanic activity of the Öræfajökull stratovolcano and the pattern of glacier fluctuations. This is explained as a response to isostatic crustal adjustment during ice cap growth and decay, and indicates a general relationship between volcanic activity and climate change.
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O'Neal, Michael Aaron. "Late Little Ice Age glacier fluctuations in the Cascade Range of Washington and northern Oregon /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6727.
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Marshall, Paul. "Palaeoenvironmental, climatic and sea-level fluctuations and sequence stratigraphy of the Scottish Bathonian." Thesis, University of Aberdeen, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325229.
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Kenzler, Michael [Verfasser]. "Ice-sheet dynamics and climate fluctuations during the Weichselian glaciation along the southwestern Baltic Sea coast / Michael Kenzler." Greifswald : Universitätsbibliothek Greifswald, 2017. http://d-nb.info/1136983570/34.
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Clarke, Shawne. "An experimental study on the influence of climatic fluctuations on solifluction, Fosheim Peninsula, Ellesmere Island, Northwest Territories." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0032/MQ38739.pdf.
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Clarke, Shawne Arianne. "An experimental study on the influence of climatic fluctuations on solifluction, Fosheim Peninsula, Ellesmere Island, Northwest Territories." Thesis, University of Ottawa (Canada), 1998. http://hdl.handle.net/10393/4538.
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A field experiment, involving direct manipulation of surface microclimate, was undertaken in the continuous permafrost zone to examine the influence of climatic fluctuations on solifluction rates and movements throughout the active layer. Movements and soil temperature were measured continuously from 1993-1997 using five electro-mechanical meters and thermocouple cables on an 8$\sp\circ$ colluvial slope in Hot Weather Creek valley, Ellesmere Island. Natural variation of movement among the years and the meters was measured until summer of 1996 when surface climatic treatments (surface warming, wetting, a combination of these two, and cooling) were performed. The longer-term effects of the treatments were monitored until August 1997. Near-surface measurements alone do not provide an accurate picture of solifluction in areas with two-sided freezing ("cold" permafrost) because there can be substantial variation in movement rates at depth. In addition, multi-year average rates potentially hide a considerable range of annual variability and do not allow for the examination of a relationship between climatic fluctuations and annual movement. (Abstract shortened by UMI.)
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Rioual, Patrick. "Diatom assemblages and water chemistry of lakes in the French Massif Central : a methodology for reconstruction of past limnological and climate fluctuations during the Eemian period." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326170.
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Giraud, Fabienne. "Recherche des périodicités astronomiques et des fluctuations du niveau marin à partir de l'étude du signal carbonaté des séries pélagiques alternantes : application au crétacé inférieur du Sud-Est de la France (Bassin vocontien)... /." Lyon : Centre des sciences de la Terre, 1995. http://catalogue.bnf.fr/ark:/12148/cb35786572m.
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Zamrane, Zineb. "Recherche d’indices de variabilité climatique dans des séries hydroclmatiques au Maroc : identification, positionnement temporel, tendances et liens avec les fluctuations climatiques : cas des grands bassins de la Moulouya, du Sebou et du Tensift." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT181/document.
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Ce travail consiste à caractériser la variabilité temporelle et spatiale des séries chronologiques de paramètres hydroclimatiques (pluies, débits) au niveau de trois grand bassins au Maroc ; (bassins de la Moulouya, du Sebou et du Tensift) et à chercher les liens entre cette variabilité hydrologique et les fluctuations climatiques matérialisées par différents indices climatiques, NAO, SOI, WMOI. L’approche d’étude est basée le traitement statistique des séries temporelles, liée aux dimensions temps et espace.Les grands bassins versants d'échelle continentale comme le Tensift, le Sebou et la Moulouya en climat méditerranéen sous influence océanique, intègrent sur des grandes surfaces la réponse hydrologique aux changements climatiques et environnementaux (fluctuations du climat, précipitations, débits) à de larges échelles spatiales et temporelles, mais également les modifications du milieu physique d’origine anthropique (changements d’occupation des sols, aménagements…), ce qui rend parfois difficile l’identification des liens entre la variabilité hydrologique et la variabilité climatique. Les principaux objectifs de ce travail sont de déterminer et de quantifier les relations entre la variabilité hydroclimatique et les fluctuations du climat à l’échelle de chaque bassin étudié et de ses principaux sous-bassins, via l'utilisation de méthodes d’analyses spectrales adaptées à l’étude des processus non stationnaires (analyse en ondelettes continues, analyse de la cohérence par ondelettes). Plusieurs modes de variabilités sont identifiés à partir de l’analyse par station (pluies et débits), du cycle annuel au mode 16-22 ans, cette analyse sera complétée par une analyse par maille, dont les données sont issues d’un fichier (SIEREM) couvrant la période 1940-1999, où on identifie des fréquences de 1an au 8-16 ans, distinguées sur des périodes différentes au niveau de chaque bassin, permettant ainsi une décomposition de la variabilité spatiale des signaux mis en évidence. Trois principales discontinuités sont identifiées en 1970, 1980 et 2000. La contribution des indices climatiques est assez importante elle est entre 55% et 80%This work is to characterize the temporal and spatial variability of hydroclimatic time series (rainfall, flow) at three large basins in Morocco; (basins of the Sebou and Moulouya Tensift) and look links between the hydrologic variability and climate fluctuation materialized by various climate indices, NAO, SOI, WMOI. The approach to study is based on statistical analysis of time series, related to time and space dimensions.The great watershed of continental scale as Tensift, Sebou and Moulouya in Mediterranean climate under oceanic influence, integrate over large areas the hydrological response to climate and environmental changes (climate fluctuations, precipitation, flows) not only to large spatial and temporal scales, but also to changes in the physical environment anthropogenic (land use changes, developments ...), which sometimes makes difficult to identify the links between hydrological variability and climate variability. The main objective of this work is to determine and quantify the relationships between hydrological variability and climate fluctuations (regionalised precipitation, climate change indexes) across each studied basin and its main sub-basins, via using spectral analysis methods adapted to the study of non-stationary processes (continuous wavelet analysis, coherence analysis wavelet). Many modes of variability are identified from the station analysis (rainfall and flow rates), the annual cycle to 16-22 years, this analysis will be complemented by a grid analysis, the data come from a (SIEREM) file covering the period from 1940 to 1999, which will allow a better understanding of the spatial variability of signals set highlighted. Which is identified frequencies the 1 year 8-16 years, distinguished different time periods at each basin, three main discontinuities identified in 1970, 1980 and 2000. The contribution of climatic indices is important enough it is between 55% and 80%
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Jakob, Kim Alix [Verfasser], and Oliver [Akademischer Betreuer] Friedrich. "Late Pliocene to early Pleistocene millennial-scale climate fluctuations and sea-level variability: A view from the tropical Pacific and the North Atlantic / Kim Alix Jakob ; Betreuer: Oliver Friedrich." Heidelberg : Universitätsbibliothek Heidelberg, 2017. http://d-nb.info/1180985788/34.
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Jakob, Kim [Verfasser], and Oliver [Akademischer Betreuer] Friedrich. "Late Pliocene to early Pleistocene millennial-scale climate fluctuations and sea-level variability: A view from the tropical Pacific and the North Atlantic / Kim Alix Jakob ; Betreuer: Oliver Friedrich." Heidelberg : Universitätsbibliothek Heidelberg, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:16-heidok-229425.
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Jallet, Arthur. "Effet de la sélection fluctuante sur le pathogène du blé Zymoseptoria tritici par une approche d'évolution expérimentale." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS349.
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Un défi important en Biologie est de comprendre comment les organismes s’adaptent à des environnements fluctuants et de déterminer l’importance relative de la plasticité phénotypique et des mutations dans cette adaptation. Nous avons examiné la réponse d’un pathogène du blé (Zymoseptoria tritici) aux fluctuations de température grâce à des approches de transcriptomique, de phénotypage (fitness relative et pathogénie) et de génomique. Pour cela, une évolution expérimentale a été menée in vitro à partir de deux clones ayant évolué dans trois régimes thermiques : à 17°C, à 23°C et en température fluctuante. Le niveau d’expression de 11% du génome a évolué de manière distincte entre les deux génotypes fondateurs en conditions de fluctuations. Nous avons également observé une plus forte densité de gènes différentiellement exprimés dans des régions connues pour être riches en éléments transposables. L’évolution en conditions fluctuantes a favorisé la robustesse du transcriptome. La fitness relative estimée dans les conditions d’évolution a augmenté uniquement pour les lignées fluctuantes issues d’un des deux génotypes fondateurs. La différence de croissance entre les deux ancêtres en conditions de fluctuations et leur différent niveau de plasticité d’expression pourraient expliquer ces résultats différents. Enfin, nous avons observé : i). des pertes de pathogénie in planta suite à l’évolution à 17°C et en fluctuations, ii). aucune perte de chromosomes accessoires, iii). de nombreuses mutations dans le génome, dont des mutations codantes dans des effecteurs. Ces travaux apportent de nombreux éléments de compréhension des mécanismes évolutifs et moléculaires sous-jacents à l’évolution de Z. tritici dans des environnements variablesAn important challenge in Biology is to understand how organisms adapt to fluctuating environments and to determine the relative significance of phenotypic plasticity and mutations in this adaptation. We examined the response of a wheat pathogen (Zymoseptoria tritici) to temperature fluctuations using transcriptomics, phenotyping (relative fitness and disease level) and genomics. With this goal, we conducted an in vitro experimental evolution from two Z. tritici clones that evolved in three thermal conditions: at 17°C, at 23°C and under temperature fluctuations. Expression level of 11% of the genome evolved in a different way between the two founder genotypes that evolved under fluctuating conditions. We also observed a higher density of differentially expressed genes in regions known to be enriched in transposable elements. Evolution under fluctuating selection promoted robustness of the transcriptome. The relative fitness estimated in the same conditions as for the experimental evolution did increase for fluctuating lineages only for one of the founder genotypes. The difference of growth between the two ancestors in fluctuating conditions and their distinct level of expression plasticity could explain these opposite results. Finally we observed: i). in planta pathogenicity losses for lineages evolved at 17°C or under fluctuations ii). no accessory chromosome loss, iii). many de novo mutations, including coding mutations in effector genes. This work contributes to shade light on the evolutionary and molecular mechanisms underlying the evolution of Z. tritici in variable environments
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Fouinat, Laurent. "Les territoires de montagne face aux changements globaux : une étude rétrospective autour de la station de ski des Deux Alpes." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAA026/document.
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Ce travail de thèse vise à reconstituer les conditions paléo-environnementales ayant eu lieu dans la vallée de l’Oisans à partir des archives naturelles représentées par les sédiments lacustres. Par une approche multi-marqueurs, nous visons à reconstituer tout à la fois : i) les fluctuations glaciaires en Oisans; ii) les modifications des activités humaines en montagne et leurs influence sur les flux de matière lors d’événements extrêmes ; iii) comprendre la relation entre changements climatiques, changements d’usage et évolution des aléas en haute montagne. Cette étude a permis de mettre en évidence les changements globaux, regroupant la variabilité climatique et les pratiques humaines, ayant influencés l’érosion autour des lacs de La Muzelle et du lac du Lauvitel durant les derniers millénaires.Les résultats principaux ont montrés que l’érosion du lac de la Muzelle a été largement dominé par l’activité glaciaire notamment avec la présence à certaines époques de fines particules détritiques liées à l’abrasion sous glaciaire. Ces dernières ont révélées une relation aux pluies torrentielles encore jamais observées auparavant, leur présence en période d’extension glaciaire étant synonyme d’une augmentation du nombre de dépôts lacustres de crues. Les activités humaines, en majeure partie représentées par l’utilisation agro-pastorale de l’espace avoisinant les lacs, ne sont clairement identifiables que lors des 300 dernières années au lac de la Muzelle. Le lac de Lauvitel est situé à une altitude moindre, dont la majorité du bassin versant est maintenant une réserve intégrale. Les études palynologiques ont mis en évidence certaines périodes d’activités humaines plus marquées. Les événements extrêmes enregistrés dans les sédiments dulac regroupent d’une part les crues, dont l’enregistrement permet une comparaison régionale de l’occurrence de ces événements et de mettre en évidence les changements de circulations atmosphériques à l’échelle des Alpes. D’autre part, les avalanches de neige lourde, dont peu d’enregistrements sont disponibles dans la bibliographie. Nous les avons identifiés grâce à l’utilisation du CT scan l’élaboration d’une nouvelle méthodologie basée sur la différence de densité relative des sédiments. Le comptage et la quantification des apports de matériel détritique grossier aux seins d’une matrice de sédiment lacustre fin, a permis d’identifier les apports liés à cet aléa au cours du temps. Nous avons ensuite reconstitué les événements d’avalanche de neige lourde déposés dans le lac de Lauvitel sur les derniers 3500 ans, dont l’occurrence intervient préférentiellement lors des périodes de retraits glaciairesThis doctoral thesis aims to a paleo-environmental reconstitution of the Oisans valley based on the natural archive of lake sediments. From a multi-proxy approach, we aim to reconstruct: i) Glacial fluctuation reconstruction in Oisans valley; ii) human activities evolution in mountain area and their influences on sediment fluxes especially during extreme events; iii)understand the relationship between climate change, use of mountain lands and natural hazard.Through this study, we identified processes of global change, comprising natural climate variability and human practices, which affected erosion patterns around Lakes Muzelle and Lauvitel during the last millennia. Main results have shown that erosion in the lake Muzelle watershed was dominated in the past by glacial activity, in particular with the presence of fine detrital particles related to subglacial abrasion. They were identified to have a relationship never observed before; during glacial extension their presence is triggering a higher number of flood deposits. At this location, human activities were identified through agro-pastoral activities and more precisely by the coprophilous fungi spore counting, revealing cattle presence since 300 years. Lake Lauvitel is located at lower altitude, which most of the watershed is now situated in an Integral Reserve. Palynological investigations lead to identification of periods of higher human activities in the valley. Extreme events recorded in Lake Lauvitel sediment are on the one hand torrential floods, which allowed a comparison with other reconstructions highlighting changes in the climatic settings in the Alps. On the other hand, wet avalanches deposits were identified with the use of a CT scan and the development of a new methodology based on relative density differences in the sediment. The counting and the quantification of coarse detrital matter within the lacustrine fine sediment matrix allowed income identification of this hazard though time. We then reconstructed wet avalanches events deposited in Lake Lauvitel during the last 3500 years, which occurrence is preferentially during glacial retreats
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Perondi, Cleiva. "Análise da eolução do ambiente proglacial das geleiras Ecology, Sphinks, Baranowski, Tower e Windy, Ilha Rei George, Antártica." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/180993.
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Esta dissertação objetiva investigar a evolução geomorfológica dos ambientes proglaciais (geleiras Ecology, Sphinx, Baranowski, Tower e Windy) da margem leste do campo de gelo Warszawa (62°12’0” S - 58°30’0” W) na Ilha Rei George, Antártica, entre 1956 - 2017. Dados obtidos por sensores remotos, como Aster GDEM2, imagens Sentinel-2 (2017) e WorldView-2 (2014), possibilitaram o mapeamento geomorfológico das formas de relevo de mesoescala proglaciais. A variação frontal e de área total das geleiras foi estimada e mapeada com dados de imagens de satélite (Sentinel-2 de 2017 e WorldView-2 de 2014) e vetores de variação frontal de 1956, 1979, 1988 e 2000. Evidenciou-se um contínuo processo de retração nas geleiras Ecology, Sphinx, Baranowski, Tower e Windy, com perda total de área de 33%, 25%, 37%, 71% e 30%, respectivamente, no período. A geleira Windy apresentou mudanças recentes em seu término de maré para terrestre, formando uma área proglacial com a exposição de formas de relevo deposicionais glaciais. Estimou-se um aumento das áreas livres de gelo de 6,3km² no período entre 1956-2017. Em resposta ao processo de retração glacial, há exposição de formas de relevo nos ambientes livres de gelo na área de estudo com a formação da rede de drenagem fluvioglacial e glaciolacustre e a formação de ambientes proglaciais com exposição de morainas laterais, frontais, latero-frontais e eskers. As áreas livres de gelo recentes são suscetíveis a processos de retrabalhamento por ação gravitacional, eólica e pluvial. Foram determinados três estágios de evolução do ambiente proglacial das geleiras associadas às feições geomorfológicas geradas em cada fase. Como mudança ambiental detectada está a sucessão de ambientes proglaciais, paraglaciais e periglaciais.This dissertation aims to investigate the proglacial geomorphological evolution (Ecology, Sphinx, Baranowski, Tower and Windy glaciers) in the western sector of Warszawa Ice Cap (62°12’0” S 58° 30’ 0” W), Admiralty Bay coast, King George Island, Antarctica between 1956 and 2017. Data obtained by remote sensors, such as Aster GDEM2, Sentinel-2 (2017) and WorldView-2 (2014) images, were applied in geomorphological mapping of the proglacial mesoscale landforms. Glacial retreat and fluctuations of glaciers areas were estimated (using Sentinel-2 images, acquired in 2017, WorldView-2 data, acquired in 2014, and outline data of the 1956, 1979, 1988 and 2000). The results evidenced the continuous retreat processes in period for Ecology, Sphinx, Baranowski, Tower and Windy glaciers, with of 33%, 25%, 37%, 71% and 30% of the area lost, respectively. The Windy glacier changed of outlet glacier for land terminus conditions in latest decades, with a recent proglacial environment development. In response to glacial retreat processes there is a glacial landforms exposition in new ice-free environments in the study area. Was recorded an increase of the 6.3km² in ice-free land areas between 1956 and 2017 in in the western sector of Warszawa Ice Cap. As response the retreat processes there are the development of the glacio-fluvial drainage network, glacio-lacustrine landforms and the formation of proglacial ice marginal environments with lateral moraines, lateral-frontal moraines, frontal moraines, eskers. Recent ice-free areas are susceptible to gravitational, wind and pluvial reworking process. Three stages of evolution of the proglacial environments of the glaciers associated with the geomorphological features formed in each phase and environmental changes in response the glacier retreat was determined. Was detected the succession of proglacial for paraglacial and periglacial environments as evidence of the environmental change.
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Austin, P. J. E. "Palaeoconductivity, lake level fluctuations and trace element history of the Aral Sea since 400 AD : assessing the impact of natural climatic variability and anthropogenic activity." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1446039/.
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As part of the INTAS funded CLIMAN project into Holocene climatic variability and the evolution of human settlement in the Aral Sea basin, fossil diatoms obtained from Chernyshov Bay in the Aral Sea have been examined in order to reconstruct conductivity and lake level change since ca. 400 AD. In an effort to establish whether fluctuations in lake level are a result of natural climatic variation or human activity across the region, the values of 613C of organic material (8I3Corg) have also been determined. The extent of anthropogenic impact on the lake has also been assessed by ascertaining the history of trace metal (Cd, Pb and Hg) contamination. Palaeoconductivity has been derived using the EDDI diatom-conductivity transfer function. Results indicate a waterbody that fluctuates between fresh and oligosaline conditions which is punctuated by three phases of elevated conductivity, all within the mesosaline range and corresponding low lake levels at ca. 400 AD, ca. 1195 - 1355 AD and ca. 1780 AD to the present day. These regressions are confirmed by diatom habitat requirements, where, due to the morphology of the lake, planktonic species are indicative of regressive phases. The C/N ratio of organic material (< 10) throughout the core indicates that 8,3Corg provides a record of within lake productivity rather than switches of vegetation in the lake's catchment. The highest values are seen to correspond with high diatom inferred conductivity and low lake levels, due to increased salinity, residence time and algai productivity. This suggests that the severity of the observed lake level changes were a result of the natural diversion of the principal source of the lake's hydrological inputs, the Amu Darya river and anthropogenic activity in the form of irrigation, social upheaval and military conflict. Since 400 AD, the trace metal record from Chernyshov Bay indicates no local or long range anthropogenic contamination of Pb and Hg. Increases of Cd over the last ca. 100 years may be related to increased fertilizer application in tandem with increased cultivation in the region.
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Meier, Wolfgang [Verfasser], Jussi [Akademischer Betreuer] Grießinger, and Jussi [Gutachter] Grießinger. "Past and recent climate variability and glacier fluctuations across the Southern Patagonian Andes - A multi‐parameter approach using tree‐ring parameters and remote sensing / Wolfgang Meier ; Gutachter: Jussi Grießinger ; Betreuer: Jussi Grießinger." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2021. http://d-nb.info/1225557976/34.
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Sanpera, Calbet Isis. "Global changes in headwater streams: effects of hydrological and nutrient fluctuations on the quality of basal resources = Canvis globals en rius de capçalera: efectes de les fluctuacions hidrològiques i dels nutrients en la qualitat dels recursos basals." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/145433.
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Streams are complex and highly diverse ecosystems. Within the stream network, headwater streams (1st to 3rd order) are highly important. Headwaters represent most of the total length, influence the structure and functioning of higher order streams, generate most of the water flow and support higher rates of biogeochemical processing, with a higher rate of nutrient removal. Moreover, they offer high habitat diversity, both within and among streams. From all the drainage basin, it is the riparian zone which has the greatest influence in the structure and functioning of these streams. The in-fall of vegetation and leaching from plant litter are major sources of energy for stream food webs. All energy available to consumers originates from primary producers from either out- or in-stream and food webs are fuelled by a complex mixture of allochthonous and autochthonous resources. In headwaters, allochthonous basal resources are generally larger than autochthonous energy sources. However, both the quantity and quality of allochthonous and autochthonous resources influence the stream structure and functioning. Quality of resources determines their potential nutritional value for the invertebrates feeding on them. The nutritional quality of organic matter (OM) can be assessed by measuring the elemental or biomolecule composition (polysaccharide, protein and lipid content). Lipids are the most efficient energy-storing compounds, and within lipids, fatty acids and sterols include essential molecules for consumers. In a context of global change, streams are highly affected by multiple direct and indirect anthropic impacts, such as climate change, land use changes and water course alterations, affecting hydrology and nutrient and light availability, which in turn affect the quality and quantity of basal resources. The aim of this thesis was to determine how environmental factors influence the quantity and quality (biochemical composition) of basal resources in headwater streams. Of the multiple environmental factors affected by global change, the present study focused on changes in hydrology and nutrient and light availability, with particular reference to headwater Mediterranean streams. This study has been mainly performed in Fuirosos, a Mediterranean stream in the northeast of the Iberian Peninsula, but also in the Mayfly creek artificial channels, in the Pacific Coast Mountains of Canada. Several methods were used, such as the measure of particulate and dissolved OM fluxes, elemental composition of OM, nutrient addition; chlorophyll content, bacterial density and extracellular enzymatic activities of biofilms, and the measurement of the biochemical quality of the basal resources. (i.e., epilithic and epipsammic biofilms, leaves and, transported particulate and dissolved OM). We have demonstrated that the El Niño Southern Oscillation (ENSO) affected riparian inputs to the stream through teleconnections that alter average precipitation (during El Niño periods, average annual precipitation was lower than in other periods, causing higher riparian inputs, due to the hydric stress of riparian trees while, during La Niña periods, precipitation was higher than at other times, leading to decreased riparian inputs). Drought periods caused a bimodal distribution of annual riparian inputs and reduced the quality of basal resources, whereas accumulated drought events diminished the riparian inputs. Floods decreased the benthic OM, increased the amount of transported OM and modified its quality. The addition of nutrients led to a decrease in carbon content, and higher light availability led to a decrease in protein content of allochthonous resources. Biofilm quality was generally higher with the addition of nutrients when light availability was higher. We consider that the nutritional quality of basal resources is a complex parameter. Whilst elemental and biochemical composition can sometimes be related, knowledge on the latter enables a better understanding of the mechanism by which abiotic changes affect the quality of resources. However, the complexity of measuring elemental composition, biochemical composition and fatty acid composition gradually increases. Hence, we suggest that the choice of the indicators of quality used would depend on the goal of the study that want to be performed and on the trade-off between analysis effort and information that wants to be obtained. Because food webs are fuelled by a complex mixture of allochthonous and autochthonous resources, the quantity and quality of these resources are limiting factors for stream secondary production. Hence, the changes observed in this study, will probably affect stream food webs.Els rius són ecosistemes complexes i molt diversos. Dins la xarxa fluvial, les rius de capçalera (de 1er a 3er ordre) tenen una gran importància. Els rius de capçalera representen la major part de la longitud total, influencien l’estructura i el funcionament dels rius d’ordre més gran, generen la major part del cabal i donen suport a taxes altes de processament biogeoquímic, amb una alta taxa d’eliminació de nutrients. A més a més, contenen un gran diversitat d’hàbitats, tant dins dels rius com entre ells. De tota la conca, és la zona ripària la que té una més gran influència en l’estructura i el funcionament d’aquests rius. La caiguda de la vegetació i el lixiviat de les fullaraca són importants fonts d’energia per les xarxes tròfiques. Tota l’energia disponible pels consumidors prové dels productors primaris tant de dins com de fora del riu i les xarxes tròfiques estan sustentades per una complexa barreja de recursos al•lòctons i autòctons. En els rius de capçalera, els recursos basals al•lòctons són generalment més importants que les fonts d’energia autòctones. Tot i això, tant la quantitat com la qualitat dels recursos al•lòctons i autòctons influencies l’estructura i el funcionament d’aquests rius. La qualitat dels recursos determina el seu valor nutritiu potencial pels invertebrats que s’alimenten d’ells. La qualitat nutritiva de la matèria orgànica (MO) es pot ser avaluada mesurant la composició elemental o de biomolècules (contingut de polisacàrids, proteïnes i lípids). Els lípids són els components d’emmagatzematge d’energia més eficients, i dins dels lípids, els àcids grassos I els esterols inclouen molècules essencials pels consumidors. En un context de canvi global, els rius estan afectats de forma molt important per múltiples impactes antròpics directes i indirectes, tals com el canvi climàtics, els canvis d’usos del sòl i les alteracions dels cursos fluvials; els quals afecten la hidrologia i la disponibilitat de nutrients i llum, els quals al seu torn, afecten la quantitat i la qualitat dels recursos basals en els rius de capçalera. Dels múltiples factors ambientals afectats pel canvi global, aquest estudi es centra en els canvis en la hidrologia i la disponibilitat de llum i nutrients, en particular als rius de capçalera Mediterranis. Aquest estudi ha estat realitzat principalment a Fuirosos, un riu Mediterrani al nord-est de la Península Ibèrica, però també als canals artificials de Mayfly creek, a les muntanyes de la costa Pacífica de Canadà. En aquest estudi s’han utilitzat diversos mètodes, tal i com la mesura dels fluxos de MO particulada i dissolta, la composició elemental de la MO, l’addició de nutrients; el contingut de clorofil•la, la densitat bacteriana i les activitats enzimàtiques extracel•lulars del biofilm i la mesura de la qualitat bioquímica dels recursos basals (és a dir, els biofilms epilítics i epipsàmics, les fulles i la MO particulada i dissolta transportada). Hem demostrar que El Niño/Oscil•lació del Sud (ENOS) va afectar les aportacions ripàries al riu a través de teleconnexions que van alterar la precipitació mitjana (durant els períodes de El Niño, la precipitació mitjana anual era més baixa, provocant un augment de les aportacions ripàries, degut a l’estrès hídric dels arbres, mentre que durant els períodes de La Niña, la precipitació era més alta que en altres moments, portant a una disminució de les aportacions ripàries). Els períodes de sequera van causar una distribució bimodal de les aportacions ripàries anuals i van reduir la qualitat dels recursos basals, mentre que els episodis de sequera acumulats van provocar la disminució de les aportacions ripàries). Les avingudes van provocar la disminució de la MO bentònica, van augmentar la quantitat de MO transportada i van modificar la seva qualitat. L’addició de nutrients va portar a una disminució del contingut de carboni, i una disponibilitat més alta de llum va provocar una disminució del contingut de proteïnes dels recursos al•lòctons. La qualitat del biofilm era generalment més alta amb l’addició de nutrients quan la disponibilitat de llum era més alta. Considerem que la qualitat nutritiva dels recursos basals és un paràmetre complex. Tot i que la composició elemental i bioquímica poden estar relacionades en alguns casos, el coneixement d’aquesta última permet una millor comprensió dels mecanismes a través dels quals els canvis abiòtics afecten la qualitat dels recursos. Tot i això, la complexitat de mesurar la composició elemental, la composició bioquímica i els àcids grassos, augmenta gradualment. Així doncs, suggerim que la tria dels indicador de qualitat utilitzats dependrà de l’objectiu de l’estudi que es vulgui realitzar i en el balanç entre l’esforç d’anàlisi i la informació que es vol obtenir. Com que les xarxes tròfiques estan sustentades per una complexa barreja de recursos al•lòctons i autòctons, la quantitat i la qualitat d’aquests recursos són factors que limiten la producció secundària en el riu. Així doncs, els canvis observats en aquest estudi, afectaran probablement les xarxes tròfiques fluvials.
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Mewis, Heike [Verfasser], Wolfgang [Akademischer Betreuer] Kießling, Liliane [Akademischer Betreuer] Rueß, and Thomas [Akademischer Betreuer] Brachert. "Ecological stability of Indo-Pacific coral reefs during Quaternary climatic fluctuations : case studies from Vanuatu and Egypt / Heike Mewis. Gutachter: Wolfgang Kießling ; Liliane Rueß ; Thomas Brachert." Berlin : Lebenswissenschaftliche Fakultät, 2016. http://d-nb.info/1093477040/34.
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Rossi, Aurélien. "Analyse spatio-temporelle de la variabilité hydrologique du bassin versant du Mississippi : rôles des fluctuations climatiques et déduction de l'impact des modifications du milieu physique." Rouen, 2010. http://www.theses.fr/2010ROUES013.
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Les grands bassins versants d'échelle continentale, comme le Mississippi, intègrent la réponse hydrologique aux changements climatiques et environnementaux (fluctuations du climat, précipitations, débits, flux sédimentaires) à de larges échelles spatiales et temporelles, mais également les modifications du milieu physique d'origine anthropique (changements d’occupation des sols, aménagements. . . ), ce qui rend parfois difficile l'identification des liens entre la variabilité hydrologique et la variabilité climatique. Les principaux objectifs de ce travail sont de déterminer et de quantifier les relations entre la variabilité hydrologique et les fluctuations du climat (précipitations régionalisées, indices climatiques) à l'échelle du bassin versant du Mississippi et de ses principaux sous-bassins ; via l'utilisation de méthodes d'analyses spectrales adaptées à l'étude des processus instationnaires (analyse en ondelettes continues, analyse de la cohérence par ondelettes). La variabilité hydrologique du Mississippi et de ses principaux affluents est structurée par plusieurs modes de variabilité, s'exprimant de l'échelle annuelle aux échelles inter-annuelle (2-4 ans, 3-6 ans, 5-8 ans), décennale (8-16 ans, 12-16 ans) et à plus long terme (22 ans, 22-26 ans). Ces modes de variabilité sont fortement similaires à ceux observés dans les précipitations (avec une cohérence moyenne de 77% à 89% selon les sous-bassins), et opèrent aux mêmes échelles de temps que la variabilité des principales fluctuations du climat affectant la région (ENSO, PDO, AMO, NAO, NAM et PNA), préalablement identifiés et synthétisés par une méthodologie similaire. La variabilité des débits du bassin versant du Mississippi se trouve influencée par un ensemble de téléconnections (cohérence de 63% à 66% en moyenne avec l'ensemble des indices climatiques), opérant toutefois à différentes échelles spatiales et temporelles, et qui évoluent au cours du temps (relations à divers degrés suivant les différentes échelles de temps, le mode de variabilité du climat mis en jeu et le sous-bassin versant considéré). De plus, la variabilité hydrologique du Mississippi et de ses principaux affluents s'inscrit plus largement dans le cadre d'une rupture majeure du système climatique et des systèmes hydrologiques à l'échelle globale observée vers 1970, qui se traduit notamment par une augmentation et une plus forte variabilité des débits, ainsi que des changements de la composition spectrale des paramètres hydrologiques et climatiques. En ce sens, la construction d'un indice "hydro-climatique unifié" à été proposée en reprenant l'ensemble des caractéristiques globales du système climatique et celles plus spécifiques à l'échelle régionale (échelle des sous bassins versants). Enfin, même si la majorité des paramètres hydrologiques se trouve apparemment très fortement liée par les paramètres climatiques, d'autres facteurs, comme les modifications du milieu physique (occupation des sols, aménagements. . . ), peuvent avoir une influence non-négligeable sur l’évolution de certains paramètres hydrologiques (hauts et bas débits), mais qui serait beaucoup plus localisée dans le temps et l'espace (i. E. , elle ne serait pas associée à l'existence d'oscillations dans l'hydrologie). A l'exception des flux hydrosédimentaires, marqués par de profonds changements qui ont pu être reliés aux aménagements du bassin versant et quantifiés par une méthodologie de modélisation spectrale (diminution des flux de sédiments en suspension exportés à l'exutoire d’environ 2,25. 108 t. An-1 sur la période 1950-1975), ces influences apparaissent spatialement localisées, et restent difficiles à caractériser. Outre leurs faibles contributions, ceci provient également du fait que ces modifications du milieu physique agissent simultanément avec d'autres facteurs pouvant modifier la réponse hydrologique, comme les changements observés dans le climat, qui reste le facteur principal des changements observésGreat River watersheds, as the Mississippi River in North America, integrate climate and environmental changes (climate fluctuations, precipitations, streamflow, sediment loads) at near-continent scale, as well as anthropogenic changes in physical environment (land uses, river management. . . ) in their hydrologic response, which makes sometimes difficult the identification of linkages between hydrological and climate variability. The main objectives of this work is to determine and quantify the relationships between hydrological variability and climate fluctuations (regionalized precipitations, climate indices) of the Mississippi River and its main tributaries, using spectral approaches adapted to (the study of non-stationary processes (continuous wavelet transform, wavelet coherence). Hydrological variability of the Mississippi River and its main tributaries is structured by several scales of variability, from annual to inter-annual (2-4y, 3-6y, 5-8y), decadal (8-16y, 12-16y) and multi-decadal scales (22y, 22-26y). These modes of streamflow variability are very similar to those observed in regionalized precipitations (mean coherency is estimated from 77% to 89% according to the sub-watershed), and operates at same time-scales variability of the main climate fluctuations affecting this region (ENSO, PDO, AMO, NAO, NAM et PNA), preliminary identified and synthesized using an similar methodology. Streamflow variability of the Mississippi River watershed appears influenced by several teleconnections (mean coherency of 63% to 66% with all climate indices), which operate at different spatial and temporal scales and change across time. Furthermore and not surprisingly, the hydrological variability of the Mississippi River and its main tributaries appears to be closely linked to a major shift in the climate system – as well as many other hydrosystems around the world – observed at global scale around 1970. This change would result in an increase in both streamflow mean and variance, as highlighted by changes in the spectral content of climate and hydrological parameters. In this way, a so-called "hydro-climatic" index was proposed in order to resume all those characteristics of the climate system that would imprint the typical scales of variability detected in the hydrological processes analyzed according to each sub-watershed. Finally, even if the majority of hydrological parameters appears strongly affected by climate parameters, others factors such as changes in physical environment (land use, river management. . . ) could also significantly influence hydrological parameters (e. G. Low and high streamflow). We could detect such human-induced changes in the variability of suspended sediment loads and show that it involved a decrease in suspended sediment loads up to 2,25. 108 metric t. Y-1 between 1950 and 1975 using a spectral modelling approach. However, the influence of these physical environmental changes in hydrology would be associated to trends or to very localized changes in space and time, rather than associated to the existence of oscillations in hydrological parameters as we could detect them. We then conclude that, despite the potential strong influence of environmental changes, climate fluctuations remain the main factor involved in the observed hydrological changes
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Dieppois, Bastien. "Etude par analyses spectrales de l'instabilité spatio-temporelle des téléconnexions basse-fréquences entre les fluctuations globales du secteur Atlantique et les climats de l'Europe du NW (1700-2010) et du Sahel ouest-africain (1900-2010)." Phd thesis, Université de Rouen, 2013. http://tel.archives-ouvertes.fr/tel-00843683.
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L'étude des impacts du changement climatique actuel est soumise à plusieurs contraintes. Premièrement, si avant la révolution industrielle la variabilité du climat est uniquement conduite sur une large gamme d'échelle par des forçages naturels, cela n'est pas le cas au XXe siècle. Deuxièmement, les effets de ce changement montrent des variations significatives à l'échelle régionale. Ainsi, sur la base d'analyses spectrales, ces travaux réexaminent l'instabilité spatio-temporelle des téléconnexions entre la variabilité climatique globale du secteur Atlantique et les climats régionaux du NW Europe et de l'Afrique de l'Ouest. L'examen des longues séries climatiques de l'Angleterre et du Nord de la France révèle des tendances similaires pour les températures, mais désappariée pour les précipitations. Différente phase de renforcement des échelles de variabilité multi- et inter-décennale ont été détectée, ce qui suggère des " fluctuations " du control climatique global. Sur ces échelles, la relation statistique entre les températures et l'Oscillation Multi-décennale Atlantique (AMO) est marquée par un changement de phase au XIXe siècle. Les précipitations semblent cohérentes avec l'indice AMO à l'échelle 30-60 ans et avec l'Oscillation Nord Atlantique (NAO) aux échelles 50-80 et 16-23 ans. Toutefois, la relation NAO/pluie présente une grande instabilité en raison des fluctuations spatiales des régimes NAO. Après le Petit Age Glaciaire, les deux pôles semblent glisser vers le SW en hiver et printemps. De plus, une fraction de la variance du champ Nord-Atlantique de pression au niveau de la mer (SLPs), capturée par l'indice NAO, pourrait être associée à d'autres régimes atmosphériques. En Afrique de l'Ouest, l'étude des fluctuations temporelles de la variabilité des précipitations sahéliennes révèle une organisation zonale, plus particulièrement exacerbée à l'échelle quasi-décennale. Les téléconnexions avec les températures de surface (SSTs) de l'Atlantique, qui s'organise différemment suivant l'échelle de variabilité, présentent également des modifications d'Est en Ouest. Au cours du XXe siècle, les précipitations au Sahel semblent rarement s'établir simultanément avec les SSTs Atlantique Nord et Tropical Sud. Une relation en phase avec les SSTs de l'Atlantique Nord s'effectue uniquement lors des périodes humides (e.g. années 1950) aux échelles multi- ou quasi-décennale. Ces téléconnexions sont orientées selon un plan NW-SE, ce qui suggère des modulations non-uniformes du balancement de la ZCIT. Les téléconnexions avec les SSTs de l'Atlantique Tropical Sud sont associées à une structure dipolaire opposant les régions guinéenne et sahélienne. Cela s'accorde donc avec des modulations de la position latitudinales de la ZCIT. Néanmoins, celle-ci dépendrait de l'échelle, de la période étudiée et de l'état des SSTs du Pacifique. Les anomalies quasi-décennales impliquées dans ces contrastes zonaux varient au cours du temps. Dans les années 1950/60, le flanc occidental de l'Afrique de l'Ouest montre des variations du flux d'Harmattan, des mouvements ascendant sur la région sahélienne et des mouvements subsidents subtropicaux. Dans les années 1970/80, des fluctuations du gradient interhémisphérique de pression et température pourrait conduire des variations du flux de mousson, et plus généralement des décalages nord/sud de la ZCIT.
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Bergamin, Rodrigo Scarton. "Variação espacial e temporal de espécies arbóreas em florestas da Mata Atlântica : perspectivas sobre o efeito das mudanças climáticas e planejamento da conservação." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/170132.
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Distintos padrões de composição de espécies de plantas podem ser observados ao longo de metacomunidades, pois espécies variam de acordo com os diferentes tipos de ambiente e também com a distância geográfica, dado o processo de dispersão. Ainda, estes mecanismos podem causar variação temporal na composição ou abundância de espécies em um sítio devido a alterações que estes mecanismos podem sofrer. Compreender como as mudanças na composição de espécies no espaço, definida como beta diversidade, ou no tempo estão relacionadas ao clima passado, atual ou futuro podem ajudar no planejamento de conservação de uma região. Assim, esta tese esta dividida em quatro capítulos e aborda questões relacionadas com mudanças espaçotemporais na composição de espécies sob uma perspectiva de planejamento de conservação e mudanças climáticas na Mata Atlântica. O primeiro capítulo apresenta um banco de dados com a informação de ocorrência de 1917 espécies de plantas arbóreas distribuídas em 206 comunidades na Mata Atlântica, em diferentes formações florestais (Floresta Atlântica stricto sensu (s.s.), Floresta com Araucária e Floresta Estacional). O segundo capítulo relacionou padrões de beta diversidade com a efetividade da rede de áreas protegidas nas formações florestais do sul da Mata Atlântica (Floresta Atlântica, Floresta com Araucária e Floresta Estacional). Encontramos altos valores de turnover e baixo aninhamento para todas as formações florestais, por isso recomendamos que esforços adicionais precisam almejar o aumento no número de áreas protegidas, especialmente para a Floresta com Araucária e a Floresta Estacional. A maioria das áreas protegidas no sul da Mata Atlântica estão concentradas na região leste, priorizando a Floresta Atlântica s.s. O terceiro capítulo trouxe novas perspectivas sobre a dinâmica da Floresta com Araucária no tempo através da modelagem de nicho ecológica. Durante as flutuações climáticas do Quaternário, estudos palinológicos indicavam uma expansão da Floresta com Araucária, porém nossos resultados demonstraram uma retração da área de cobertura desta floresta, principalmente nas zonas de contato com outras formações florestais. Também observamos que futuramente, se a temperatura continuar aumentando como previsto, a Floresta com Araucária sofrerá uma drástica redução na sua distribuição. Por fim, o capítulo quatro investigou como as espécies de árvores estão respondendo aos efeitos de mudanças climáticas em parcelas permanentes localizadas em ecótonos de florestas Atlânticas. Os resultados mostram que espécies tropicais estão migrando em direção a áreas de maior altitude, ou seja mais frias. Espécies tropicais que já ocorrem em áreas vi de Floresta com Araucária estão apresentando maiores taxas de recrutamento e crescimento, e menor mortalidade do que espécies temperadas, características da Floresta com Araucária.Distinct patterns of plant species composition can be observed along metacommunities, as species vary in relation to different types of environment and also to the geographic distance, given the dispersal process. These mechanisms may yet lead temporal variation in species composition or abundance in a given place due to fluctuations on these mechanisms. Understanding how changes in species composition across the space, defined as beta diversity, or in time are related with past, current and future climate changes can help conservation planning in a given region. Thus, this thesis is divided into four chapters and discusses shifts in species composition across space and time under the perspective of conservation planning and climate changes in the Atlantic Forest. The first chapter shows a database with 1917 tree species occurrence distributed in 206 sites across distinct forest formations in the Atlantic Forest biome (Atlantic Rainforest, Araucaria Forest and Seasonal Forest). The second chapter related beta diversity patterns with the effectiveness of the current network of protected areas in southern Brazilian Atlantic forests (Atlantic Rainforest, Araucaria Forest and Seasonal Forest). We found high values of turnover and low nestedness for all forest formations, thus additional conservation efforts must target an increase in the number of protected areas, especially for the Araucaria Forest and the Seasonal Forest. Most protected areas are currently limited to the eastern region and prioritize the Atlantic Rainforest. The third chapter brought new insights about the Araucaria Forest dynamics in time through ecological niche models. During the climatic fluctuations of the Quaternary, palynological studies indicated an expansion of the Araucaria Forest, however our results demonstrated an overall retraction of the cover area, mainly in boundary zones with other forest formations. Yet, we showed that in the future, if the temperature continues to increase as expected, the Araucaria Forest would suffer a drastic reduction in its distribution. Finally, the fourth chapter investigated how tree species are responding to climatic changes in permanent plots located in Atlantic forests ecotones. Our results showed that tropical species are migrating towards to colder areas in higher altitudes. Tropical species that already occur in Araucaria Forest areas are even presenting higher rates of recruitment and growth, and lower mortality than temperate species characteristics from the Araucaria Forest.
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Piuco, Roberta da Cruz. "Flutuação populacional, variação morfométrica e assimetria flutuante em Pygoscelis papua, no arquipélago das Shetlands do Sul, Antártica." Universidade do Vale do Rio dos Sinos, 2013. http://www.repositorio.jesuita.org.br/handle/UNISINOS/3331.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
CNPQ – Conselho Nacional de Desenvolvimento Científico e Tecnológico
UNISINOS - Universidade do Vale do Rio dos Sinos
INCT-APA - Instituto Nacional de Ciência e Tecnologia Antártico de Pesquisas Ambientais
Programa Antártico Brasileiro
SECIRM - Secretaria Interministerial para os Recursos do Mar
MMA - Ministério do meio Ambiente
O pinguim-papua (Pygoscelis papua) reproduz a partir de 46°S a 65°S. Apesar de sua ampla distribuição são consumidores costeiros e não migratórios, possuem um alto nível de filopatria e as populações estão restritas a ilhas de reprodução e faixas de forrageamento e apresentam variações contrastantes entre populações. Esta tese tem como objetivos: 1) avaliar as respostas do tamanho da população reprodutiva de pinguim-papua de acordo com fatores climáticos em Stinker Point, Ilha Elefante; 2) identificar o dimorfismo sexual de tamanho em caracteres morfométricos em adultos reprodutores de pinguins-papua em Stinker Point, Ilha Elefante, comparando-se com a técnica de sexagem molecular. Além disso, verificar a variação morfométrica da espécie em três locais do Arquipélago das Shetlands do Sul e comparar com dados da literatura e 3) quantificar um tipo potencial de assimetria em pinguins-papua nas ilhas Elefante e Rei George, caracterizando seus níveis assimétricos como uma forma de avaliar a qualidade do ambiente. A população reprodutiva de pinguim-papua respondeu significativamente ao Índice de Oscilação Antártica e à anomalia de temperatura durante o início do período reprodutivo. Provavelmente pelas variações climáticas extremas interferirem na decisão dos indivíduos de reproduzir ou não em um determinado ano. Na avaliação do dimorfismo sexual, através de medidas morfométricas, o comprimento do bico foi a medida de maior dimorfismo sexual (5,3%) e classificou corretamente 76,7% das aves, sendo em média as fêmeas maiores que os machos. Dentre as medidas morfométricas analisadas, todas apresentaram diferenças entre os locais do Arquipélago das Shetlands do Sul e Península Antártica. Dada a pouca acurácia das funções discriminantes na sexagem e as diferenças das medidas morfométricas conforme a área geográfica de pinguim-papua, é preciso ter cautela ao classificar indivíduos com base em uma única avaliação, de forma que a sexagem molecular apresentou melhor resultado. Quanto ao tipo de assimetria, os níveis observados refletem um padrão de assimetria flutuante (AF), porém sem diferença significativa. A ausência de altos níveis de AF indica que não há níveis cumulativos suficientes de estresses ambientais que pudesse causar distúrbios fisiológicos e alterar a homeostase do desenvolvimento normal nesta espécie na Antártica.
Gentoo penguin (Pygoscelis papua) breed from 46ºS to 65ºS. Despite its wide distribution are inshore consumers and non-migratory, have a high level of philopatry and populations are restricted to island breeding and foraging ranges and shown variations contrasting among populations. This thesis aims to: 1) to evaluate the breeding population size responses of the Gentoo penguin according to climate factor at Stinker Point, Elephant Island; 2) to identify the sexual dimorphism of size in the morphometric characteristics of male and female adult Gentoo penguins at Stinker Point, Elephant Island, compared with the technique of molecular sexing. Furthermore, to verify morphometric variation of the specie at three sites f the South Shetlands Archipelago and compare with literature data and 3) to quantify one kind of potential asymmetry in Gentoo penguins, breeding at Elephant and King George Islands and attempt to characterize their extremes of variation as a way of evaluating the current living quality of the environment. The breeding population size of Gentoo penguin responded significantly to the Antarctic Oscillation Index and the temperature anomaly during the early reproductive period. Probably by extreme climatic variations affecting the decision on breeding or skipping breeding in a given year. In the assessment of sexual dimorphism using morphometric characters, the bill length was the larger measure of sexual dimorphism (5.3%) and correctly classified 76.7% of the birds, were found females larger than males. Among the morphometric measurements analyzed, all showed differences among the sites of the South Shetlands Archipelago and Antarctic Peninsula. Given the limited accuracy of the discriminant function sexing and differences of these morphometric measurements according to the geographical area of Gentoo penguin, is necessary have caution to classify individuals based on a single assessment, so that the molecular sexing presented best result. For the type of asymmetry, the levels of asymmetry reflect a fluctuating asymmetry (FA) pattern, however no significant difference. Absence of high levels of observed FA in our study led us to think it indicates there are not sufficient cumulative levels of environmental stresses such that they might cause physiological disturbances and alter the homeostasis of normal development in this species in Antarctica.
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FIGUEIRÊDO, Bárbara Camboim Lopes de. "Análise multifractal da velocidade do vento em Pernambuco." Universidade Federal Rural de Pernambuco, 2014. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/4526.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The study of climate has great importance, given that a variation of climatic elements affect the economy of a certain region and life of the inhabitants. Climate variables temperature, humidity, atmospheric pressure, solar radiation, precipitation and wind can be affected by geophysical and environmental factors such as latitude, altitude, air mass, proximity to sea, sea currents and vegetation. Wind is the most complex climate element representing the natural phenomenon of turbulence, it is characterized by high temporal and spatial variability. Wind is generated by atmospheric air mass movement, and has influence on various environmental phenomena such as soil erosion, pollutant dispersal and transport of pollen and seeds. Knowing wind speed temporal and spatial distribution is crucial to evaluate the potential for generation of eolic energy. In this work we study long-term correlations in wind speed temporal series registered at twelve meteorological stations in the state of Pernambuco, Brazil. To this end we apply Multifractal Detrended Fluctuation Analysis (MF-DFA) on hourly wind speed data for the period 2008-2011. All the analyzed series exhibit multifractal properties with generalized Hurst exponents above 0.5 indicating persistent temporal dynamics for both, small and large fluctuations. We also calculate other multifractal measures Rényi exponent and singularity spectrum, and complexity parameters, position of maximum, width and asymmetry of multifractral spectrum. No correlation was detected between complexity parameters and the geographic parameters longitude, latitude and altitude of the station, except for asymmetry of multifractal spectrum: negative correlation with longitude for maximum wind speed and negative correlation with latitude for average wind speed. However for all stations the strength of multifractality (indicated by width of multifractal spectrum) is greater for maximum wind speed then for average wind speed. These results contribute to a better understanding of the nature of stochastic processes governing wind dynamics which is necessary for development of more accurate predictive models for wind speed temporal variability and diverse phenomena influenced by wind.
O estudo do clima tem grande importância visto que a variação em elementos climáticos afeta a economia de uma região e a vida das pessoas que ali habitam. As variáveis climáticas temperatura, umidade, pressão atmosférica, radiação solar, precipitação e vento podem ser influenciadas por diversos fatores, geofísicos e ambientais, tais como latitude, altitude, massas de ar, continentalidade e maritmidade, relevo e vegetação. Um dos mais complexos elementos do clima é o vento, pelo fato de representar um fenômeno natural de turbulência, caracterizado por uma grande variabilidade temporal e espacial. O vento é gerado pelo movimento das massas de ar e pode influenciar vários fenômenos ambientais como erosão do solo, dispersão de poluentes e transporte de pólen e sementes. O conhecimento da distribuição temporal e espacial da velocidade do vento é crucial para avaliação do potencial eólico de uma região. Neste trabalho estudaram-se correlações de longo alcance das séries temporais de velocidade do vento registradas em 12 estações meteorológicas durante o período de 2008 a 2011 no estado de Pernambuco aplicando-se o método Multifractal Detrended Fluctuation Analysis (MF-DFA) nas séries temporais horárias. Todas as séries analisadas mostram as propriedades multifractais com valores de expoente generalizado de Hurst acima de 0,5 indicando uma dinâmica persistente para pequenas e grande flutuações. Foram calculadas também as outras medidas multifractais, o expoente Rényi e o espectro multifractal bem como os parâmetros de complexidade: posição do máximo, largura e assimetria do espectro multifractal. Não foram encontradas correlação entre os parâmetros de complexidade e as coordenadas geográficas: longitude, latitude e altitude, exceto a medida de assimetria do espectro multifractal: correlação negativa entre a rajada e longitude e entre velocidade e latitude. Para todas estações as larguras do espectro multifractal foram maiores para a rajada que para a velocidade, indicando uma multifractalidade mais forte. Estes resultados contribuem para uma melhor compreensão da natureza dos processos estocásticos geradores da dinâmica do vento, necessária para o desenvolvimento de modelos confiáveis para predição da variabilidade temporal do vento e dos diversos fenômenos influenciados pelo mesmo.
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Behrooz, Roozbeh. "Phylogéographie de deux reptiles iraniens (le complexe Montivipera raddei et Ophisops elegans) et implication pour la conservation." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEP001.
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Les espèces de haute altitude (Sky-Islands) sont parmi les taxons les plus sensibles aux changements environnementaux et une meilleure connaissance de ces espèces (répartition, groupes génétiques, histoire d’évolution, etc.) est indispensable afin de définir les unités adaptées pour la conservation. Cette thèse a porté sur l’analyse moléculaire de deux gènes mitochondriaux (Cyt b et ND4) chez le groupe d’espèces Montivipera raddei et un gène mitochondrial (COI) chez l’Ophisops elegans dans les montagnes d’Iran qui sont des centres d’endémisme importants pour les reptiles. En me basant sur les données génétiques, je propose de considérer toutes les montivipère d’Iran comme une seule espèce ; Montivipera raddei comprenant trois sous-espèces ; Montivipera raddei albicornuta (nord du Zagros, Zanjan et nord-ouest de l’Iran jusqu’en Turquie), Montivipera raddei latifii (Alborz), et Montivipera raddei kuhrangica (centre du Zagros). Les temps de divergences obtenus entre les clades de montivipères semblent montrer des changements de la connectivité des populations pendant le Pléistocène qui résulte de l’effet fort des oscillations climatiques durant cette époque, notamment pendant les interglaciaires. Ce travail a aussi révélé une grande diversité génétique au sein des clades iraniens d’ophisops élégant ce qui pose la question de l’existence d’espèces/sous-espèces cryptiques en Iran. Finalement, ce travail a permis de définir des ESU pour les montivipères et l’ophisops élégant et notamment je propose que toutes les populations isolées du groupe d’espèces M. raddei et d’O. elegans montrant des haplotypes propres soient considérées comme des ESU pour la conservationHigh-altitude species (Sky-Islands) are among the most sensitive taxa to environmental changes and a better knowledge of these species (distribution, genetic groups, evolutionary history, etc.) is essential in order to define the adapted units for the conversation. This thesis focused on the molecular analysis of two mitochondrial genes (Cyt b and ND4) in the Montivipera raddei (Radde's Rock Viper) species group and a mitochondrial gene (COI) in Ophisops elegans (Snake-Eyed Lizard) in the mountains of Iran, which are important centers of endemism for reptiles. Based on the genetic data, I propose to consider all the Iranian montivipers as one species; Montivipera raddei comprising three subspecies; Montivipera raddei albicornuta (north of Zagros, Zanjan and northwestern Iran to Turkey), Montivipera raddei latifii (Alborz), and Montivipera raddei kuhrangica (central Zagros). The times of divergence between the clades of montivipers seem to show changes in the connectivity of populations during the Pleistocene, which results from the strong, effect of climatic oscillations during this period, especially during interglacial periods. This work also revealed a great genetic diversity within the Iranian clades of snake-eyed lizard, which raises the question of the existence of cryptic species / subspecies in Iran. Finally, this work made it possible to define ESUs for montivipers and snake-eyed lizards. In particular, I propose that all isolated populations of the M. raddei species group and O. elegans showing specific haplotypes to be considered as ESUs for conservation
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Lombard, Alix. "Les variations actuelles du niveau de la mer : Observations et causes." Phd thesis, Université Paul Sabatier - Toulouse III, 2005. http://tel.archives-ouvertes.fr/tel-00079969.
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Alors que depuis un peu plus de 2000 ans, le niveau moyen de la mer a peu varié, ce niveau s'est élevé d'environ 2 mm/an au cours du 20ème siècle. Cette hausse soudaine est attribuée au réchauffement climatique d'origine anthropique enregistré depuis plusieurs décennies. Depuis une douzaine d'années, on mesure de façon globale et précise les variations du niveau de la mer grâce aux satellites altimétriques Topex/Poseidon et Jason-1. Ces observations indiquent une hausse moyenne globale d'environ 3 mm/an depuis 1993, valeur sensiblement plus grande que celle des dernières décennies. Diverses observations disponibles depuis peu nous ont permis de quantifier les contributions des divers facteurs climatiques à la hausse observée du niveau de la mer : expansion thermique de la mer due au réchauffement des océans, fonte des glaciers de montagne et des calottes polaires, apport d'eau des réservoirs continentaux. Le bilan de ces nouvelles observations nous permet d'expliquer en partie la hausse observée du niveau de la mer. En particulier, nous montrons que l'expansion thermique des océans n'explique que 25% de la hausse séculaire du niveau de la mer enregistrée par les marégraphes depuis 50 ans, tandis qu'elle contribue à la hauteur de 50% à la montée du niveau marin au cours de la dernière décennie. Parallèlement, des études récentes estiment que la fonte des glaciers de montagne et des calottes polaires pourraient contribuer pour environ 1 mm/an à l'élévation du niveau de la mer au cours de la dernière décennie.
De plus, la forte variabilité régionale des vitesses d'évolution du niveau de la mer révélée par les observations altimétriques de Topex/Poseidon résulte en grande partie de l'expansion thermique. Nous mettons également en lumière l'importante variabilité spatio-temporelle décennale de l'expansion thermique des océans au cours des 50 dernières années, qui semble dominée par les fluctuations naturelles du climat. De plus nous posons pour la première fois la question du lien qui existe entre les fluctuations décennales de l'expansion thermique des océans et la contribution climatique des eaux continentales au niveau de la mer. Enfin, une analyse préliminaire des observations gravimétriques de la mission spatiale GRACE sur les océans nous permet d'évaluer les variations saisonnières du niveau moyen de la mer liées aux variations du bilan de masse d'eau des océans.
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Meyssignac, Benoit. "La Variabilité Régionale du Niveau de la Mer." Phd thesis, Université Paul Sabatier - Toulouse III, 2012. http://tel.archives-ouvertes.fr/tel-00779038.
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Au cours du XXème siècle, les mesures marégraphiques ont permis d'estimer la hausse du niveau de la mer global à 1.7 mm.a-1. Depuis deux décennies, les observations faites par les satellites altimétriques indiquent une hausse du niveau de la mer plus rapide, de 3.2 mm. a-1 sur la période 1993-2011. Grâce à leur couverture quasi-globale, les observations spatiales ont aussi révélé une forte variabilité régionale dans la hausse du niveau de la mer qui dépasse de beaucoup la hausse moyenne globale dans de nombreuses régions du globe. Cette composante régionale qui s'ajoute à la hausse globale pour donner le niveau de la mer total local, est essentielle dans l'étude des impacts de la hausse du niveau de la mer sur les régions côtières et les îles basses. Dans cette thèse, nous analysons les observations de la variabilité régionale de la hausse du niveau de la mer, nous proposons une reconstruction de cette variabilité régionale depuis 1950 (i.e. avant l'avènement de l'altimétrie spatiale) et nous étudions ses causes et ses origines. Tout d'abord, nous proposons une reconstruction de la variabilité régionale du niveau de la mer dans le passé (avant la période altimétrique) en combinant des données marégraphiques avec les structures spatiales propres de l'océan déduites des modèles d'océan. Cette méthode permet de reconstruire le niveau de la mer en 2 dimensions depuis 1950, sur la majeure partie du globe, avec une résolution proche de celle de l'altimétrie spatiale. Ensuite, nous appliquons la méthode de reconstruction pour estimer la variabilité régionale de la hausse du niveau de la mer passée dans trois régions sensibles au réchauffement climatique : le Pacifique tropical, la mer Méditerranée et l'océan Arctique. Nous en déduisons pour ces régions la hausse totale ( régionale plus moyenne globale) du niveau de la mer local au cours des dernières décennies. Pour les sites où l'on dispose de mesures du mouvement de la croûte terrestre, nous évaluons la hausse local du niveau de la mer relatif (i.e. hausse du niveau de la mer totale plus mouvement de la croûte local) depuis 1950. Le but est de permettre les études de l'impact local de la hausse du niveau de la mer aux échelles climatiques. Enfin, nous analysons l'origine de la variabilité régionale de la hausse du niveau de la mer pour déterminer si elle est due à l'activité anthropique ou si elle résulte de la variabilité naturelle du système climatique. Nous nous focalisons sur le Pacifque tropical qui est marqué par une très forte variabilité régionale de la hausse du niveau de la mer depuis 1993. Grâce a la reconstruction du niveau de la mer depuis 1950, nous montrons que cette variabilité régionale récente (17 dernières années) n'est pas stationnaire dans le temps mais qu'elle fluctue en lien avec une basse fréquence du mode de variabilité ENSO. Avec les modèles de climat du projet CMIP3, nous montrons de plus que cette variabilité régionale est essentiellement d'origine naturelle (variabilité interne du système climatique) et que l'impact anthropique y est trop faible pour l'instant pour y être détecté.
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Favillier, Adrien. "Impacts du changement climatique sur l’activité des avalanches dans les Alpes : apports de la dendrogéomorphologie pour la reconstitution spatiotemporelle de l’activité des avalanches dans un contexte de changements environnementaux dans les hautes vallées du Guil et du Rhône Disentangling the impacts of exogenous disturbances on forest stands to assess multi-centennial tree-ring reconstructions of avalanche activity in the upper Goms Valley (Canton of Valais, Switzerland) Spatio-temporal maps of past avalanche events derived from tree-ring analysis: a case study in the Zermatt valley (Valais, Switzerland) Tree-ring reconstruction of snow avalanche activity: Does avalanche path selection matter? Non-stationarities induced by land-cover changes in dendrogeomorphic reconstructions of snow avalanche activity: Insights from the Queyras massif (French Alps) Complex signals in regional tree-ring reconstructions of snow avalanches: lessons from the Goms valley (Swiss alps) Impacts des fluctuations climatiques sur l’activité des avalanches dans le Queyras." Thesis, Université Clermont Auvergne (2017-2020), 2019. http://theses.bu.uca.fr/nondiff/2019CLFAL024_FAVILLIER.pdf.
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Au 20ème siècle, les massifs montagneux, dont les Alpes, ont connu un réchauffement significatif avec une augmentation des températures deux fois plus importante que la moyenne mondiale. Un tel réchauffement altère les composantes de la cryosphère. Elle induit, par exemple, un passage des précipitations solides aux précipitations liquides, des phases de fonte des neiges plus fréquentes et plus intenses, ainsi qu’une forte diminution de la quantité de neige et une réduction de la durée de la couverture neigeuse. Aux horizons 2050–2100, les modèles climatiques prévoient que l'épaisseur du manteau neigeux sera considérablement réduite et que les propriétés de la neige, et notamment la stabilité du manteau neigeux, seront modifiées. Ces changements devraient entraîner des modifications importantes dans l'activité des avalanches. Parallèlement, l’afforestation induite par la déprise agro-sylvo-pastorale, la démocratisation des sports d'hiver et l'urbanisation des versants ont profondément modifié les paysages de montagne depuis le milieu du 18ème siècle, de même que l'exposition des individus. Dans ce contexte, une documentation précise de l'activité passée des avalanches est cruciale pour mettre en évidence et comprendre les impacts du réchauffement climatique sur l'activité avalancheuse. Jusqu'à présent, cette documentation s'appuyait sur des chroniques historiques ou des observations systématiques. Cependant, les premières sont souvent discontinues et axées sur des événements catastrophiques, tandis que les secondes se limitent à la seconde moitié du 20ème siècle, excluant toute comparaison avec des périodes climatiques distinctes – tel que les phases froides du Petit Âge Glaciaire, par exemple. Sur les versants forestiers, l'approche dendrogéomorphique apparaît être un complément fiable aux archives historiques et aux séries d'observations systématiques, car elle permet de reconstruire l'activité passée des avalanches, en continu, à l‘échelle des plusieurs siècles, avec une résolution annuelle. Pourtant, jusqu'à présent, même si de nombreuses reconstructions locales ont été proposées, la fiabilité de l’approche a été peu souvent analysée et aucune chronologie régionale – cruciale pour distinguer les interférences potentielles entre l'activité des avalanches, les fluctuations climatiques et les changements socio-économiques – n'a été développée dans les Alpes. Dans cette thèse de doctorat, des avancées méthodologiques significatives ont été réalisées afin (1) d’améliorer la détection des avalanches dans les cernes de croissance, (2) d’éliminer les non-stationnarités liées à la diminution du nombre d'arbres au cours du temps dans les reconstructions et (3) d’agréger les reconstructions locales en chronologies régionales. Sur la base de ces développements, des chronologies régionales pluriséculaires homogénéisées ont été développées (4) pour 10 couloirs d’avalanche de la vallée de Goms (Valais, Alpes suisses, 1880-2014) et (5) 11 couloirs du massif du Queyras (Alpes françaises, 1560-2016). Ces dernières ont été confrontées aux fluctuations climatiques et aux changements d'occupation du sol. À Goms, l'absence de signal climatique clair dans la chronologie régionale souligne les interférences induites par les non-stationnarités locales et démontre qu’une stratégie d'échantillonnage à l'échelle régionale devra nécessairement constituer un préalable au développement d’une chronologie robuste. Dans le massif du Queyras, la forte diminution de l'activité avalancheuse observée au cours du 20ème siècle est attribuée au réchauffement climatique et au processus d’afforestation des versantsFor the 20th century, high mountain areas, such as the Alps, have undergone a significant warming with temperature increase twice as much as the global average. Such warming strongly alters the cryosphere components. It induces, for example, a shift from solid to liquid precipitation, more frequent and more intense snowmelt phases or a strong decrease in the amount and duration of snow cover, especially at the elevation of the snowrain transition. In the future, climate models forecast that snow depth will be significantly reduced and that snow properties such as snow stability will be modified. These changes in snow cover characteristics and amounts are expected to induce significant changes in snow avalanches activity. At the same time, afforestation induced by the abandonment of agriculture and grazing, the democratization of winter recreation activities and the urban sprawl on the slopes have strongly modified the mountain landscapes since the mid-18th century as well as the exposition of individuals to snow avalanches. In this context, a precise documentation of past snow avalanche activity is crucial to decipher and to understand the impacts of the undergoing climate warming on the snow avalanche activity. To date, this documentation usually relies on historical chronicles or systematic observations. However, the firsts are often discontinuous and focused on catastrophic events. The seconds are limited to the second half of the 20th century thus precluding a comparison from climatically distinct period. On forested paths, the dendrogeomorphic approach is theoretically a reliable approach complement to historical archives and series of systematic observation to infer past snow avalanche activity. Yet, so far, the robustness of this approach has been poorly questioned and no regional chronology, crucial to disentangle potential interferences between snow avalanche activity, climate fluctuations and socio-economic changes, has been developed in the Alps. In this PhD thesis proposes new methodological frameworks to (1) detect avalanche events from tree-ring series, (2) remove non-stationarities related to the decreasing number of trees over time in the reconstruction and (3) aggregate locals reconstructions in regional chronologies. Based on these development, homogenized multicentennial regional chronologies developed (4) for 10 paths of the Goms Valley (Valais canton, Swiss Alps, 1880-2014) and (5) 11 paths from the Queyras Massif (French Alps, 1560-2016) are confronted to climatic fluctuations and land use changes. At Goms, the absence of clear climatic signal in the regional chronology evidence the interference with local nonstationarities and question the need for a sampling strategy at the regional scale to create a robust chronology. In the Queyras massif, the strong decrease of avalanche activity observed over the 20th century is attributed to global warming and to the afforestation process
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Huang, Pao-Wei, and 黃寶緯. "Climate variability responsible for the rainfall fluctuation in Indian." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/73zdur.
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