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Huff, Amy K. "Multiple stable oxygen isotope analysis of atmospheric carbon monoxide and its sources /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9835376.
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Vaiglova, Petra. "Neolithic agricultural management in the Eastern Mediterranean : new insight from a multi-isotope approach." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:c8824136-da35-43b2-a700-f458d0cc2fdf.
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The work presented in this dissertation explores the nature of agro-pastoral strategies developed by Neolithic farmers as a way to understand how early food production was inter-twined with environmental and socio-economic opportunities and constraints. Towards this end, a multi-isotope approach is used to address questions of scale and intensity of crop cultivation and animal management at the archaeological sites of Kouphovouno, southern Greece, Makriyalos, northern Greece, and Çatalhöyük, south-central Turkey. Measurements of stable carbon, nitrogen, oxygen and strontium isotope values of carbonized plant remains, human and animal bone collagen and animal tooth enamel are used to examine the similarities and differences in the types of treatments that individual species of plants and animals received during the agricultural cycle at the distinct locations. The results show that farmers at the three sites developed variable methods for exploiting the arable and pastoral landscape and catering to their economic and culinary needs. The discussion considers the implications of these findings to our understanding of the complexity and adaptability of early farming systems.
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Lee, Vanessa Eileen. "Characterising dissolved nitrate in precipitation using stable nitrogen and oxygen isotopes /." Internet access available to MUN users only, 2005. http://collections.mun.ca/u?/theses,18576.
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Ahmed, Shakib. "Stable isotopic study of groundwater arsenic contaminated plume at Shepley's Hill Landfill." Thesis, Boston College, 2014. http://hdl.handle.net/2345/3876.
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Thesis advisor: Rudolph HonIn the northeast United States, arsenic (As) contamination in groundwater is frequently associated with historical landfill leachate plumes. Based on the history of Shepley's Hill Landfill (SHL) in Devens, MA, solid waste disposal activities spanned nearly a century of landfilling with little or no documentation of when or what waste material was disposed. Past geochemical investigations proved the presence of high levels of As in groundwaters within and around the SHL region. A total of 114 samples were collected from the SHL region and analyzed for their hydrogeochemistry and isotopic signature. Since the isotopic ratios of äD and ä18O can potentially be influenced by the mobilization process of As, this study attempts to identify any correlations between the stable isotopic ratios and the hydrogeochemistry of SHL waters. The results of the groundwater hydrogeochemical analysis show multiple relationships between metal concentrations and As concentration levels, typical of groundwater undergoing redox reactions. The result of the stable isotope analysis show significant fractionation of stable isotope ratios away from the meteoric water line. However, the role of strong redox gradients and various redox ladder reactions involving water did not produce a significant correlation with the isotopic fractionations present within different zones of the landfill. In most cases, the fractionations stand independent of the increase/decrease in As concentration and can be attributed to either unrelated chemical reactions within groundwater or evaporation
Thesis (MS) — Boston College, 2014
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Earth and Environmental Sciences
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Crosby, Maria Rose. "A Late Pleistocene to Mid-Holocene Stable Oxygen Isotope Record from a Belize Stalagmite." Thesis, Boston College, 2010. http://hdl.handle.net/2345/1393.
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Thesis advisor: Amy E. FrappierA ~7,000 year stable isotope record from a Central American stalagmite is presented as a record of rainfall and consequently Intertropical Convergence Zone (ITCZ) tropical rain belt strength over the late Pleistocene to mid-Holocene. The "amount effect" explains the well-documented inverse relationship between rainfall amount and stable oxygen isotope values observed in tropical monsoon regions and consequently in stalagmite calcite from those regions. ITCZ rainfall influences much of the Central American tropical region and here a ~7,000 year stable isotope record from stalagmite ATM1 harvested from Actún Tunichil Muknal Cave in Belize is presented as a record of ITCZ influenced rainfall during the late Pleistocene to mid-Holocene (5,561 ± 2,488 BP - 12,605 ± 284 BP). Three major oxygen isotope excursions occur within the record. These excursions correspond to the global cold Younger Dryas and 8.2 ka events and a relatively undocumented wet period around 6,300 bp. The Younger Dryas manifests as a relatively moist period in central Belize while the 8.2 ka event manifests as a relatively dry period. The reason for the opposite responses to cooling elsewhere in the globe is posited to be due to orbital forcings. The 6,300 bp relatively wet period appears to be synoptic in scale and two possible triggers for the isotope excursion are presented: eustatic sea level rise causing lagoonal constriction, warming of water off the coast of Belize, and thus increased evaporation and precipitation over the study region; and hurricane clusters, evidenced in the region in the succeeding 1,000 years, in which the location of the Azores High funnels hurricanes to make landfall near the central Belize region. ATM1 provides evidence for tropical leads and/or lags to global climate events and bolsters the idea that high and low latitude climate relationships are complexly interlinked
Thesis (MS) — Boston College, 2010
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Geology and Geophysics
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Bedaso, Zelalem K. "Stable Isotope Studies of Paleoenvironment and Paleoclimate from Afar, Ethiopia." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3004.
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ABSTRACT
The sedimentary deposits of the Hadar Formation at Dikika and the Mount Galili Formation at Galili preserve a wealth of paleoenvironmental and paleoclimatic records spanning the last 5.29 Ma. Stable carbon and oxygen isotopic compositions of herbivore tooth enamel were analyzed for more than 600 specimens of 15 different taxa from 10 stratigraphic intervals. The application of carbon and oxygen isotopes here aims
principally at reconstructing shifts in the relative abundance of C4 grasses, and its implications for climate indicators including temperature, aridity, and seasonality. The full range of δ13Cenamel values throughout the Plio-Pleistocene signifies a wide range of foraging strategies by the fauna, which in turn reflects the mosaic of vegetation at Dikika and Galili. Estimates of ecosystem carbon isotope composition (δ13Cecosystem , which is given by average δ13Cenamel of each large vertebrate taxon weighted by the respective faunal abundance and the estimated daily biomass consumption) is used to asses shifts in the ecosystem-scale proportion of C3 and C4 vegetation. In the Plio-Pleistocene, the general paleoenvironmental conditions varied from wooded grassland to grasslands with the total amount of C4 grass cover on the landscape varying between 35% and 91%. Likewise, the paleohabitat reconstructions indicate the presence of grassland, wooded grassland, woodland habitats throughout the Pliocene and in Middle Pleistocene but the relative proportion of the habitats has changed substantially with time. Although this result agrees with the general trend towards more open grassland since the Late Miocene, a rebound of closed habitats and C3 resources from closed canopy woodlands or forests is evident in the middle Pliocene between 3.42 Ma and 3.24 Ma. These changes in the proportion of habitats could have affected the distribution and availability of preferred food resources and has an implication on the interaction of the animals on the paleolandscape and competition for resources.
18Oenamel values also show a wide range of variation within each stratigraphic member and through time. Temporal variation of δ13Cenamel values within a given taxon, as well as differences among sympatric taxa, document different aspects of the environment and climate, including changes in drinking water source, seasonality, and periods of strong
evaporation. Estimated δ13Cmeteoric water based on the most 18O-depleted hippo tooth enamel, displays values of -1.94 / (VSMOW) and -5.24 / (VSMOW) in the Middle Pleistocene of Asbole and middle Pliocene of Galili, respectively. A major shift in the isotopic composition of water at ~ 3.0 Ma was accompanied by a 6.0 / increase from middle Pliocene to the present. While a +3.8 / shift from early to middle Pliocene was documented. The isotopic composition of meteoric water between 4.6 Ma and 4.38 Ma was most 18O-enriched compared to the rest of the Pliocene estimates. Likewise, an increase in the estimated δ13Cmeteoric water values was documented in the Awash Valley and elsewhere in East Africa, which indicate a regional climate change since the early Pliocene. An increase in the aridity, which is expressed as mean annual water deficit (i.e., the difference between potential evapotranspiration and mean annual precipitation) is also evident since the early Pliocene. These changes during the Pliocene in the region may in part be attributed to a regional decrease in the amount of precipitation and changes in the moisture source superimposed on global climate changes.
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Collett, Martin. "Multi-proxy stable oxygen and carbon isotope evidence for Holocene climate change in western Ireland." Thesis, University of Liverpool, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250327.
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Twiddy, Edward James. "Applications of stable carbon and oxygen isotope analysis to some aspects of coastal environmental change." Thesis, Durham University, 1996. http://etheses.dur.ac.uk/1582/.
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Nakai, Wataru. "Examination of stable oxygen isotope as a tree ring proxy of tropical ring-less trees." Kyoto University, 2019. http://hdl.handle.net/2433/242922.
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Larsson, Simon. "A high-resolution oxygen isotope reconstruction of humidity changes in central Sweden during the late Holocene." Thesis, Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-105982.
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Records of stable oxygen isotope variations from a variety of proxies have been used in palaeoclimatic research since the 1950’s. Several studies have applied stable isotope analysis of lake sediments to reconstruct past climate changes in central and northern Sweden, including a study of Lake Blektjärnen in Jämtland, central Sweden, by Andersson (2010). In this study, sediments from that same lake were sampled for stable isotope analysis of bulk carbonates with the aim to improve the resolution of the isotopic record for the last two millennia. The results indicate a shift from relatively drier to wetter conditions between ~2,300–1,300 cal. years BP, generally wet conditions close to the Medieval Warm Period (~1,000–750 cal. years BP) and generally dry conditions during the Little Ice Age (~550–150 cal. years BP). These results are in agreement with previous palaeoclimatic reconstructions in the region. The isotopic record of Lake Blektjärnen was completed for the last ~2,350 years at a resolution of ~15 years per sample, three times higher than that of the previous study, displaying the advantages of bulk carbonate sampling for stable isotope analysis and providing a high-resolution dataset on humidity changes in central Sweden during the late Holocene.
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Brookman, Tom Hugo. "Stable isotope dendroclimatology of New Zealand kauri (Agathis australis (D. Don) Lindl.) and cedar (Libocedrus bidwillii Hook. F.)." Thesis, University of Canterbury. Department of Geological Sciences, 2014. http://hdl.handle.net/10092/9027.
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This thesis presents research that improves our understanding of the relationship between climate and tree-ring stable isotopes in New Zealand kauri (Agathis australis (D. Don) Lindl.) and cedar (Libocedrus bidwillii Hook. F). As a whole, this research creates a framework from which future investigations of stable isotope dendroclimatology can pursued at high temporal resolution across longer term temporal intervals. Such a framework is required to realize the full potential of New Zealand tree-ring records as archives of palaeoclimatic information. In the Southern Hemisphere, mid-to-high latitude terrestrial climate proxy records are sparse; the long-lived endemic conifers of New Zealand present a rare opportunity to gain valuable insight into Late-Quaternary and Holocene climatic change.
A major barrier to long stable isotope dendroclimatic proxy records has been the time-and-resource intensive nature of associated sample preparation and analytical processes. Through experimental assessment of the SBrendel α-cellulose extraction method, this research demonstrates that this simple processing method can, with some caveats, be successfully applied to resinous conifers, facilitating rapid chemical preparation of samples. Further efficiency gains are documented in through use of dual element low temperature pyrolysis of cellulose, providing carbon and oxygen stable isotope determinations on a single sample, rather than the traditionally separate analyses. These preliminary investigations into methodological efficiency enabled the ~3000 stable isotope determinations on kauri and cedar, on which the following investigations into isotopic variability, chronology quality and climate-isotope relationships are based.
Both kauri and cedar exhibit substantial intra and inter-tree isotopic variability, resulting in greater than normal sample numbers being required to isolate the common variance in composite time-series. Despite sampling 7 trees (18 cores) at one site and 8 trees (21 cores) at another, only oxygen isotope time-series reach an Expressed Population Signal score of 0.85, a common benchmark of chronology quality. Further investigations using high-resolution sequential sampling of single rings show that this variability extends to a sub-annual scale. Within single rings there are large ranges in δ13C and δ18O, generally corresponding with regular annual cycles of up to 4.6‰ for δ13C and 8.1‰ for δ18O. These data show high frequency (sub weekly) changes in δ18O, demonstrating sufficiently fine resolution for event-to-seasonal scale climate/weather reconstruction. However, that potential is complicated by the lack of strong climatic correlations with isotopic cycles.
Due to their stronger common signal, δ18O time series are investigated for inter-annual stable isotope dendroclimatic reconstruction from kauri and cedar. Bootstrapped correlation and multiple regression models show strong relationships between kauri and cedar δ18O and relative humidity, accumulated rainfall and soil moisture deficit. The correlations are strongest for all variables during the period from Autumn prior to growth to the current growth summer. Tree-ring δ18O in kauri and cedar is identified as an effective recorder of regional hydroclimate leading up to and during the Austral growth season.
While it is demonstrated that tree-ring δ18O holds significant promise for inter-annual palaeoclimate reconstruction, it is equally apparent from this research that stable isotope dendroclimatology in New Zealand faces significant challenges. Foremost is gaining an improved understanding of seasonal dendrochemical cycles and their relationship with tree-physiology. Increasing the spatial and temporal coverage of tree-ring isotope records is vital to realising New Zealand’s vast potential for stable isotope dendroclimatic reconstruction.
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Padgett, Abbey E. "Early-Middle Holocene Cultural and Climate Shifts in NW Africa: Paleoenvironmental Reconstruction Using Stable Isotopes of Land Snail Shells." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1522318834405742.
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Schollaen, Karina. "Tracking climate signals in tropical trees : new insights from Indonesian stable isotope records." Phd thesis, Universität Potsdam, 2014. http://opus.kobv.de/ubp/volltexte/2014/7194/.
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The tropical warm pool waters surrounding Indonesia are one of the equatorial heat and moisture sources that are considered as a driving force of the global climate system. The climate in Indonesia is dominated by the equatorial monsoon system, and has been linked to El Niño-Southern Oscillation (ENSO) events, which often result in severe droughts or floods over Indonesia with profound societal and economic impacts on the populations living in the world's fourth most populated country. The latest IPCC report states that ENSO will remain the dominant mode in the tropical Pacific with global effects in the 21st century and ENSO-related precipitation extremes will intensify. However, no common agreement exists among climate simulation models for projected change in ENSO and the Australian-Indonesian Monsoon. Exploring high-resolution palaeoclimate archives, like tree rings or varved lake sediments, provide insights into the natural climate variability of the past, and thus helps improving and validating simulations of future climate changes.
Centennial tree-ring stable isotope records | Within this doctoral thesis the main goal was to explore the potential of tropical tree rings to record climate signals and to use them as palaeoclimate proxies. In detail, stable carbon (δ13C) and oxygen (δ18O) isotopes were extracted from teak trees in order to establish the first well-replicated centennial (AD 1900-2007) stable isotope records for Java, Indonesia. Furthermore, different climatic variables were tested whether they show significant correlation with tree-ring proxies (ring-width, δ13C, δ18O). Moreover, highly resolved intra-annual oxygen isotope data were established to assess the transfer of the seasonal precipitation signal into the tree rings. Finally, the established oxygen isotope record was used to reveal possible correlations with ENSO events.
Methodological achievements | A second goal of this thesis was to assess the applicability of novel techniques which facilitate and optimize high-resolution and high-throughput stable isotope analysis of tree rings. Two different UV-laser-based microscopic dissection systems were evaluated as a novel sampling tool for high-resolution stable isotope analysis. Furthermore, an improved procedure of tree-ring dissection from thin cellulose laths for stable isotope analysis was designed.
The most important findings of this thesis are: I) The herein presented novel sampling techniques improve stable isotope analyses for tree-ring studies in terms of precision, efficiency and quality. The UV-laser-based microdissection serve as a valuable tool for sampling plant tissue at ultrahigh-resolution and for unprecedented precision. II) A guideline for a modified method of cellulose extraction from wholewood cross-sections and subsequent tree-ring dissection was established. The novel technique optimizes the stable isotope analysis process in two ways: faster and high-throughput cellulose extraction and precise tree-ring separation at annual to high-resolution scale. III) The centennial tree-ring stable isotope records reveal significant correlation with regional precipitation. High-resolution stable oxygen values, furthermore, allow distinguishing between dry and rainy season rainfall. IV) The δ18O record reveals significant correlation with different ENSO flavors and demonstrates the importance of considering ENSO flavors when interpreting palaeoclimatic data in the tropics.
The findings of my dissertation show that seasonally resolved δ18O records from Indonesian teak trees are a valuable proxy for multi-centennial reconstructions of regional precipitation variability (monsoon signals) and large-scale ocean-atmosphere phenomena (ENSO) for the Indo-Pacific region. Furthermore, the novel methodological achievements offer many unexplored avenues for multidisciplinary research in high-resolution palaeoclimatology.Die tropischen Gewässer um Indonesien sind eine der äquatorialen Wärme- und Feuchtigkeitsquellen, die als treibende Kraft des globalen Klimasystems betrachtet werden können. Das Klima in Indonesien ist geprägt durch das Australisch-Indonesische Monsunsystem. Weiterhin besteht eine Verknüpfung mit El Niño-Southern Oszillation (ENSO) Ereignissen, die oft zu schweren Dürren oder Überschwemmungen in der Region mit tiefgreifenden gesellschaftlichen und wirtschaftlichen Folgen führen. Der neueste IPCC-Bericht legt dar, dass ENSO auch in den nächsten 100 Jahren das vorherrschende Klimaphänomen im tropischen Pazifik bleiben wird. Ferner wird davon ausgegangen, dass sich die ENSO-bezogenen Niederschlagsextrema intensivieren werden. Wenig Übereinstimmung herrscht jedoch bislang zwischen den Klimasimulationsmodellen in Bezug auf die voraussichtlichen Veränderungen von ENSO und dem Australisch-Indonesischen Monsunsystem. Hochaufgelöste Paläoklima-Archive, wie z.B. Jahrringe oder warvierte Seesedimente, geben Auskunft über die natürliche Klimavariabilität der Vergangenheit und können somit dazu beitragen, die Computersimulationen der künftigen Klimaentwicklung zu verbessern und zu validieren. Hundertjährige stabile Jahrring-Isotopenchronologien | Das Hauptziel dieser Doktorarbeit war es, dass Potenzial von tropischen Jahrringen zur Aufzeichnung von Klimasignalen herauszustellen und deren Evaluierung als Paläoklimaproxys. Im Detail wurden stabile Kohlenstoff- (δ13C) und Sauerstoff- (δ18O) Isotopenverhältnisse in Teakbäumen analysiert, und die ersten gut replizierten hundertjährigen (AD 1900-2007) stabilen Isotopenchronologien aus Java (Indonesien) erstellt. Dabei wurden verschiedene klimatische Einflussgrößen getestet, ob diese signifikante Korrelationen mit den Jahrringparametern aufzeigen. Weiterhin wurden hochaufgelöste intra-annuelle Sauerstoffisotopenzeitreihen erstellt, um den Transfer des saisonalen Niederschlagssignals in den jeweiligen Jahrring zu bemessen. Die ermittelte Sauerstoff-Isotopenchronologie wurde anschließend auf mögliche ENSO Signale hin untersucht. Methodische Errungenschaften | Ein zweites Ziel dieser Arbeit war es neue Verfahren zur Analyse stabiler Isotope in Baumjahrringen zu entwickeln und zu optimieren. Zwei verschiedene UV-Lasermikrodissektions-Systeme wurden getestet als neues präzises Präparationswerkzeug für stabile Isotopenstudien. Darüber hinaus wurde eine verbesserte Methode für die Probenaufbereitung stabiler Isotopenmessungen anhand von Zellulose-Dünnschnitten entwickelt. Die wichtigsten Ergebnisse dieser Doktorarbeit sind: I) Die hier vorgestellten neuartigen Techniken zu Probenvorbereitung verbessern die Analyse stabiler Isotope für Jahrringstudien in Hinsicht auf Präzision, Effizienz und Qualität. Es wurde gezeigt, dass die UV-Lasermikrodissektion eine wertvolle Technik ist, um die Beprobung von Pflanzengewebe in höchster Auflösung und beispielloser Präzision durchzuführen. II) Es ist gelungen, einen Leitfaden für ein modifiziertes Verfahren der Zelluloseextraktion an Gesamtholz-Dünnschnitten und der anschließenden Jahrringaufbereitung zu erstellen. Diese neuartige Methode optimiert die Analyse stabiler Isotopenzeitreihen in zweierlei Hinsicht: schnellere und effiziente Zelluloseextraktion und präzise Trennung der Jahrringsequenzen in inter-annueller bis intra-annuelle Auflösung. III) Die hundertjährigen stabilen Jahrring-Isotopenchronologien weisen signifikante Korrelationen mit dem regionalen Niederschlag auf. In den hochaufgelösten stabilen Sauerstoffisotopenwerten spiegelt sich deutlich das Niederschlagssignal der Trocken- und der Regenzeit wieder. IV) Die stabile Sauerstoffisotopenzeitreihe zeigt signifikante Korrelationen mit verschiedenen ENSO Phasen. Dies betont, dass die verschiedenen ENSO Phasen bei der Interpretation von tropischen Paläodaten zu berücksichtigen sind. Die Ergebnisse der Dissertation zeigen, dass saisonal aufgelöste stabile Sauerstoffisotopenchronologien von indonesischen Teakbäumen ein geeigneter Proxy für mehrhundertjährige Rekonstruktionen der regionalen Niederschlagsvariabilität (Monsun-Signale) und großräumiger Ozean-Atmosphären-Systeme (ENSO) für den Indopazifik ist. Darüber hinaus bieten die neuartigen methodischen Errungenschaften viele neue Ansätze für multidisziplinäre hochaufgelöste Studien in der paläoklimatologischen Forschung.
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Underwood, Sandra Jean. "Stable isotope (18 O/16 O and D/H) studies of cascade volcanic arc magmatism." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/underwood/UnderwoodS0509.pdf.
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Al-Qattan, Nasser M. E. N. A. A. "Interpretation of Oxygen Isotopic Values (d18O) of North American Land Snails." Miami University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=miami1404460805.
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Myers, David John. "OXYGEN AND HYDROGEN STABLE ISOTOPE RATIOS IN MISSISSIPPI RIVER FLOODPLAIN INVERTEBRATES: IMPLICATIONS FOR DISPERSAL AND FOOD WEB ANALYSIS." OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/311.
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Understanding energy fluxes within and between floodplain water bodies, and between rivers and their floodplains is essential for comprehending the dynamics of modern, altered river systems. Floodplain aquatic invertebrates may move between habitats deliberately (through emergence and dispersal) or through passive transport during flooding. This movement may represent a significant flux of energy and an essential food web subsidy. I assessed the usefulness of the stable isotopes of hydrogen and oxygen (D and 18O respectively) for identifying the origins and movements of macroinvertebrates in Mississippi River floodplain water bodies. I sampled water and invertebrates from the Mississippi River, intermittent and permanent floodplain wetlands, and tributaries during 2007 and 2008. Results showed consistent relationships between δD and δ18O signatures in invertebrate tissues and their home water bodies. I also investigated whether δD and δ18O could be used as a multivariate "fingerprint" to trace a captured invertebrate back to its environment of origin. Results showed that δD can be a useful tracer of the movement of floodplain invertebrates in some cases, although δ18O is likely not suitable for that purpose.
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Birkos, Elizabeth. "Controls on Stable Oxygen Isotope Concentrations in Coropuna and Quelccaya Peruvian Ice Cores Over the Last 200 Years." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1238093120.
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Currens, Benjamin J. "DEUTERIUM AND OXYGEN-18 DIFFUSION IN A CONFINED AQUIFER: A NUMERICAL MODEL OF STABLE ISOTOPE DIFFUSION ACROSS AQUITARD-AQUIFER BOUNDARIES." UKnowledge, 2016. http://uknowledge.uky.edu/ees_etds/40.
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The stable isotopes 2H and 18O, combined with noble gases and radioisotopes (e.g., 3H, 14C, 36Cl), are used to infer groundwater age and climate during recharge. Flow regimes within low-velocity flowpaths and long residence times could allow an aquitard-aquifer diffusive flux to alter isotope abundance. Consequently, the diffusion of isotopes (e.g., 14C, 2H and 18O) between aquifers and confining layers needs to be considered in such conditions. In this study, COMSOL Multiphysics was used to determine if diffusion of 18O (and 2H by proxy) from a bounding aquitard could explain observed downgradient enrichment of 2H and 18O within a regional aquifer. Using the geologic and hydraulic properties of the lower Wilcox aquifer of the Mississippi Embayment aquifer system in Missouri and Arkansas, the advection-dispersion equation was solved along a 1-D groundwater flow domain, coupled with a cross-contact aquitard-aquifer diffusive flux. Although the observed signal within the lower Wilcox was not matched, a sensitivity analysis indicated the importance of the isotope composition gradient between the aquifer and aquitard. Furthermore, groundwater velocity was suggested as a controlling influence on aquitard-aquifer exchange that could alter aquifer isotope composition.
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Gentry, David Keith. "Seasonal isotope and trace-metal profiles of serially-sampled Conus gastropods: proxies for paleoenvironmental change." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/3871.
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We test the fidelity of shallow-water gastropod skeletons as multi-proxy archives of seasonal paleo-environmental change by performing isotopic and trace-metal analyses on specimens of Conus ermineus from the Gulf of Mexico. Four adult specimens were collected from Stetson Bank in the Flower Garden Banks National Marine Sanctuary during the summer of 2002. Shell samples were milled along axes of growth to produce time-series profiles spanning up to eight years. We corrected the profiles for growth rate effects and compared the tuned results with in situ temperature and salinity records at the reef surface and temperature profiles from nearby surface buoys. Examination of sample densities in δ18O cycles shows that shell growth is faster during summers and slower during winters. Tuning the profiles versus time yields δ18O values that co-vary closely with seasonal temperatures to a high degree of coherency (R2 = 0.84). The δ13C profiles show cyclic variation modified by ontogenetic decreases in δ13C. These ontogenetic trends are attributable to decreasing metabolic efficiency, while seasonal cycles reflect hydrographic changes in the gastropods habitat. Salinity and δ13C of dissolved inorganic carbon show a strong correlation at Stetson Bank (R2 = 0.80), and early summer shell δ13C minima coincide with local salinity minima during times of peak river discharge. The terminations of these δ13C minima occur during annual upcoast reversals of shelf currents in this area. These effects are augmented by summer stratification and productivity minima that further decrease seawater δ13C. Sr/Ca ratios increase through ontogeny, most likely due to decreasing metabolic efficiency. However, seasonal variations in Sr/Ca profiles show strong similarity with δ18O profiles, confirming the temperature dependence of Sr/Ca and minimal influence of salinity on shell δ18O at Stetson Bank. The results of this study show that tuned δ18O and Sr/Ca profiles can be used to reconstruct seasonal paleotemperatures. Carbon isotope profiles and environmental data also demonstrate the utility of Conus δ13C as a proxy for freshwater flux and shelf circulation.
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Rebenack, Carrie E. "A Carbon and Oxygen Stable Isotope-Dendrochronology Study of Trees from South Florida: Implications for the Development of a High-Resolution Subtropical Paleoclimate Record." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/3009.
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The global paleoclimate archive is lacking in tropical dendrochronology studies as a result of limitations from inconsistent tree-ring production imposed by precipitation-driven seasonality. The slash pine, Pinus elliottii Engelm. var. densa, is the dominant canopy species of Big Pine Key (BPK) rocklands and has been shown to produce complicated, but distinct, ring structures; however, traditional dendrochronology studies have not established correlations between ring width measurements and major climate drivers controlling South Florida precipitation. My study utilized the carbon (δ13C) and oxygen (δ18O) isotope records in the α-cellulose component of tree-rings to extract information about the physiological responses of trees to climate and tropical cyclone activity. The δ13C measurements in the earlywood and latewood of four P. elliottii var. densa trees were used to build a chronology (1922-2005) and to distinguish annual growth from intra-annual density fluctuations (IADFs). Empirical orthogonal functions were used to determine individual response to precipitation, El Niño-Southern Oscillation (ENSO), and the Atlantic Multidecadal Oscillation (AMO). There is a distinct relationship between the δ13C values of cellulose and ENSO; however the nature (direct vs. inversely correlated) is temporally controlled by the prevailing phase of the AMO. The appearance of some IADFs coincide with the timing of El Niño winters occurring during the cool AMO phase, resulting in enriched δ13C values. The additional precipitation may encourage tree growth, but subsequent dry periods may slow growth and cause the tree to employ water-conservation strategies. Tree growth is influenced by the major climate drivers and the control they exert over the timing of precipitation; however, growth is ultimately controlled by the microenvironment surrounding individual trees. The δ18O and δ13C values of the latewood cellulose were compared to tropical cyclone activity occurring within a 100km radius of BPK. Tropical storms and depressions appeared as anomalously depleted values in the δ18O residual record, reflecting large amounts of tropical rain. The effects of hurricanes varied by storm; however, many of the major hurricanes (category 3-5) were preserved as an enrichments in the δ13C value of the following earlywood season. The application of stable isotope analyses greatly increases the breadth of paleoclimate information available from the trees.
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Morin, Samuel. "Analyse de la composition isotopique de l'ion nitrate dans la basse atmosphère polaire et marine." Phd thesis, Université Paris-Est, 2008. http://tel.archives-ouvertes.fr/tel-00326229.
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Les oxydes d'azote atmosphériques (NOx=NO+NO2) sont des composés clefs en chimie de l'environnement, jouant un rôle central pour la capacité oxydante de l'atmosphère et le cycle de l'azote. La composition isotopique du nitrate atmosphérique (NO?3 particulaire et HNO3 gazeux), constituant leur puits ultime, renseigne sur leur bilan chimique. Le rapport 15N/14N donne une indication de leurs sources, alors que l'anomalie isotopique en oxygène (?17O=d17O-0.52×d18O) révèle la nature de leurs mécanismes d'oxydation. Des études couplées de d15N et ?17O d'échantillons de nitrate atmosphérique collectés dans l'Arctique, en Antarctique et dans l'atmosphère marine au dessus de l'Océan Atlantique, où le bilan des NOx est souvent mal connu ont été effectuées. À ces fins, le défi que constitue la mesure simultanée des trois rapports isotopiques du nitrate (17O/16O, 18O/16O et 15N/14N) dans le même échantillon représentant moins d'une micromole a été relevé. La solution adoptée tire avantage des propriétés d'une bactérie dénitrifiante, utilisée pour convertir le nitrate en N2O, dont la composition isotopique totale a été mesurée en utilisant un système automatisé de chromatographie en phase gazeuse et spectrométrie de masse de rapport isotopique. Les principaux résultats obtenus via les isotopes de l'oxygène permettent l'identification claire de transitions saisonnières entre voies d'oxydation des NOx, y compris le rôle majeur des composés halogénés réactifs au printemps polaire en régions côtières. Les isotopes de l'azote ont quant à eux permis d'apporter de nouvelles contraintes sur le cycle de l'azote dans les régions polaires, grâce au fractionnement significatif induit par les phénomènes de remobilisation post-dépôt affectant le nitrate dans le manteau neigeux, et l'émission de NOx qui en découle
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Hamilton, Bryan T. "Small Mammals in portions of Great Basin National Park Susceptible to Groundwater Withdrawal: Diversity and Stable Isotope Perspectives." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/1705.
Full textAbstract:
To support population growth in Las Vegas, Nevada, large scale increases in groundwater pumping are planned across the state. This pumping could affect riparian areas in Great Basin National Park by lowering groundwater levels, reducing stream flows, and xerifying riparian vegetation. Great Basin National Park (GBNP) is mandated to manage its resources unimpaired for future generations. Loss of biodiversity is unacceptable under this mandate. If groundwater levels are reduced beyond a threshold, aquatic and riparian diversity would be lost, but the effects on small mammal communities are less clear. To provide baseline information and to consider the effects of groundwater withdrawal a priori, we sampled and compared small mammal communities in two watersheds susceptible to groundwater withdrawal and one non-susceptible watershed. We also used to stable isotopes of nitrogen, carbon, deuterium and oxygen to characterize small mammal communities. Evenness was higher in susceptible watersheds, which were distinct in species composition. Riparian and upland habitats in susceptible watersheds supported complementary small mammal communities, while communities in the non-susceptible watershed were more homogenous. Susceptible watersheds are located at the lowest elevations of GBNP where habitat heterogeneity due to the contrast between mesic riparian and xeric upland habitats is important in maintaining small mammal diversity. Partitioning was primarily seen in nitrogen and carbon isotopes which reflect feeding ecology (trophic level and primary production source), but was also seen in oxygen isotopes. Major differences in nitrogen and carbon isotopes were between taxonomic groups, while similarity was highest within these groups. Shrews and ermine were highest in nitrogen reflecting their high trophic positions. Harvest and piñon mice were intermediate in nitrogen suggesting omnivory, while chipmunks, voles, woodrats and pocket mice were apparently herbivorous. Carbon ratios were consistent with C3 based diets but were relatively enriched in Sigmodontinae species. Small mammal deuterium was similar to stream water suggesting that stream water is an important water source of water to small mammals. Oxygen enrichment relative to stream water and precipitation suggested that small mammals are sensitive to body water evaporation. Contrary to a previous study, oxygen isotopes were inversely related to water use efficiency. Increases in the rate of groundwater pumping adjacent to Great Basin National Park could lower water tables, reduce stream flows, and xerify riparian vegetation. We suggest that groundwater levels, streams flow and riparian vegetation, in addition to small mammal species composition will be important response variables in monitoring the effects of groundwater withdrawal. If predictions of groundwater withdrawal are realized, groundwater levels, stream flows, vegetation, microclimate, and invertebrates riparian dependent as well as small mammals will be negatively affected resulting in a decrease in diversity and loss of riparian species from affected areas.
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Munizzi, Jordon. "Changes in Neolithic Subsistence Patterns on Flores, Indonesia Inferred by Stable Carbon, Nitrogen, and Oxygen Isotope Analyses of Sus from Liang Bua." Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5681.
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Despite an abundance of archaeological material recovered from sites in Island Southeast Asia, the timing and route by which cultigens first arrived in Wallacea remains unclear. Many of the staple crops now grown on these islands were domesticated in mainland Asia, and were deliberately introduced by humans at an unknown point during the Holocene, through several possible routes. In this study, the δ13C, δ15N and δ18O values of subfossil bones and teeth attributed to Sus celebensis and Sus scrofa are analyzed. These materials, which span the last 5160 years at Liang Bua, Flores, Indonesia are used to determine if and when there was a shift towards agricultural intensification, and whether this intensification included the integration of domesticated C4 crops. The δ13C and δ15N values of the bone and dentin collagen samples indicate an abrupt shift towards enrichment in 13C and depletion in 15N at some time between 5160 and 2750 yBP. This hints at changes in human subsistence patterns that may have included the clearing of forests, and the integration of non-endemic C4 cultigens such as foxtail millet (Setaria italica) onto the island. No statistically significant variation in the δ18O values of the enamel carbonate samples over time is observed, suggesting that once they appeared on Flores, semi-domesticated pigs became an important part of the island ecosystem, and were bred and raised on Flores instead of being continuously imported from elsewhere.M.A.
Masters
Anthropology
Sciences
Anthropology
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Roberts, Patrick. "Fruits of the forest : human stable isotope ecology and rainforest adaptations in Late Pleistocene and Holocene Sri Lanka." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:9f314a01-b062-4a9c-9f55-7db943294866.
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Despite ecological, anthropological, and archaeological debate surrounding their desirability as habitats for human occupation, tropical rainforests have received relatively little attention in discussions of Homo sapiens' Pleistocene dispersal. Sri Lanka has yielded some of the earliest dated fossil and material culture evidence (c. 38-35,000 cal. years BP) for our species in a modern rainforest context beyond Africa. Nevertheless, assertions in Sri Lanka, and elsewhere, regarding early human rainforest reliance have been largely based on coarse or 'off-site' palaeoenvironmental records, and the overall role of these environments in human subsistence strategies has remained uncertain. This study applies stable carbon and oxygen isotope analysis to Sri Lankan human fossil, and associated faunal, tooth enamel dated to between 36-29,000 and 3,000 cal. years BP, in order to directly test human rainforest resource reliance, reconstruct a stable isotope ecology, and develop 'on-site' palaeoenvironmental records for Late Pleistocene-Holocene Sri Lankan rainforest foragers. Stable carbon and oxygen isotope analysis of modern Sri Lankan primates, and stable carbon, oxygen, and nitrogen isotope analysis of modern plant samples from the Polonnaruwa Nature Sanctuary, are also performed to investigate the ecology of Sri Lankan primates on which Late Pleistocene-Holocene forager subsistence strategies were focused. The results demonstrate that Homo sapiens relied on rainforest resources in Sri Lanka from c. 36-29,000 cal. years BP until the Iron Age c. 3 cal. years BP, even when open environments, and their corresponding resources, were available. This remains the case through periods of evident environmental change at the Last Glacial Maximum and even upon the arrival of agriculture in the island's tropical forests. The primate stable isotope data prove difficult to interpret as ecological niche separation in the absence of observation data. Nonetheless, humans were evidently able to not only use but also rapidly specialise in the exploitation of South Asia's rainforests.
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Rowell, Kirsten. "Isotopic Logs of The Sea of Cortez: Oxygen and Carbon Stable Isotopes in Otoliths of Marine Fish Record the Impact of Diverting the Colorado River from the Sea." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/194512.
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I use microchemistry in fish otoliths to test the hypothesis that diverting Colorado River flow from reaching the Gulf of California has impacted two endemic fish: the threatened gulf Corvina, (Cynoscion othonopterus) and the endangered totoaba (Totoaba macdonaldi). The oxygen and carbon stable isotope ratios in otoliths help to reconstruct conditions of the environment during key life history stages before and after the damming and diverting the Colorado River. The δ¹⁸O in otoliths illustrate that both C. othonopterus and T. macdonaldi seek out brackish habitat provided by the Colorado River during their early life history. The δ¹⁸O of C. othonopterus otolith have a strong negative correlation with Colorado River flow. I found that previously published relationships between otolith δ¹⁸O and ambient temperature along with δ¹⁸O of the water are sufficient to predict ranges of expected δ¹⁸O values for T. macdonaldi in the field. The δ¹⁸O in pre-dam T. macdonaldi otoliths show significant divergence from modern T. macdonaldi otoliths’ values, indicating that these fish used the brackish waters of the Colorado River estuary. The δ¹³C in T. macdonaldi otoliths has a significant proportion of its δ¹³C derived from diet. Pre-dam T. macdonaldi juveniles have a significantly different diet, which reflects that the Colorado River estuary had higher productivity before diversion of the river. Lastly, T. macdonaldi grew faster before the dams and in association with Colorado River flow measured by the δ¹⁸O.
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Roden, John S., James A. Johnstone, and Todd E. Dawson. "Regional And Watershed-Scale Coherence In The Stable-Oxygen and Carbon Isotope Ratio Time Series in Tree Rings Of Coast Redwood (Sequoia Sempervirens)." Tree-Ring Society, 2011. http://hdl.handle.net/10150/622643.
Full textAbstract:
Coast redwood (Sequoia sempervirens) ecosystems are strongly influenced by the presence of
summer marine fog, and variation in fog frequency is closely linked to climate variation in the NE Pacific region. Because oxygen isotope composition (𝛿¹⁸O) of organic matter records distinct water sources (e.g. summertime fog vs. winter precipitation) and carbon isotopes (𝛿¹³C) are typically sensitive to humidity and water status, it then follows that inter-annual variation in tree-ring isotope ratios, which are coherent across multiple sites, should preserve a potentially powerful proxy for climate reconstruction. Here we present an analysis of a 50-year time series for both 𝛿¹⁸O and 𝛿¹³C values from subdivided tree rings obtained from multiple redwood trees at multiple sites. Within-site and between site correlations were highly significant (p < 0.01) for the 𝛿¹⁸O time series indicating a regionally coherent common forcing of 𝛿¹⁸O fractionation. Within-site and between-site correlation coefficients were lower for the 𝛿¹³C than for the 𝛿¹⁸O time series although most were still significant (at least to p < 0.05). The hypothesized reason for the differences in the correlation is that carbon isotope discrimination is more sensitive to microenvironmental and tree-level physiological variation than is 𝛿¹⁸O fractionation. Stable-isotope variation in tree-ring cellulose was similar between slope, gully and riparian micro-habitats within a single watershed, implying that minor topographic variation when sampling should not be a major concern. These results indicate that stable-isotope time series from
redwood tree rings are strongly influenced by regional climate drivers and potentially valuable proxies for Pacific coastal climate variability.
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Jones, Penelope Jean. "Climate change, water stress and agriculture in the Indus Civilisation, 3000-1500 BC." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/270736.
Full textAbstract:
This thesis investigates the relationship between climate, agriculture and social change in South Asia’s Bronze Age urban Indus Civilisation. Specifically, my research tests the hypothesis that an abrupt weakening of the Indian Summer Monsoon ca 2100 cal BC led to increasing crop water stress, and hence potentially contributed to the Civilisation’s decline by reducing food supply. This hypothesis is frequently invoked in discussions of the Civilisation’s end, yet until now, has not been empirically tested. Using material excavated from several Indus settlements, this study uses a novel combination of isotopic techniques to directly test the connection between climate change and agricultural stress. These techniques are first, oxygen isotope analysis of faunal bones and teeth; and second, stable carbon isotope analysis of crop remains. The oxygen analyses provide detailed records of monsoon intensity at a local, human scale, while the carbon analyses provide an empirical test of whether crop water stress increased. Applied in parallel across a diverse suite of Indus sites, these techniques together provide an archaeologically and ecologically-nuanced analysis of climatic impacts. The archaeological analyses are supported by a methodological study, which investigates how water status relates to the stable carbon isotope signature in barley (Hordeum vulgare) and the Indian jujube (Ziziphus mauritiana) along a climatic transect in north-western India today. Overall, the isotopic results suggest that at the sites sampled here, climate change probably had minimal impacts on crop water availability. This does not necessarily mean that climate change had no impacts on agriculture across the greater Indus sphere, and indeed there are hints that there may have been climatic stress in more vulnerable settings. However, at the sites studied here, any hydrological consequences of climate change—including the 4.2 ka event—appear to have had neither a lasting nor a pervasive impact on the adequacy of crop water supply. This is an important finding, and necessitates a clear refinement of how we think about climatic sensitivity, climatic vulnerability, and climatic impacts across—and indeed beyond—the greater Indus.
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Grant, George W. "Characterization and climate reconstruction of the Ekblaw site, Quttinirpaaq NationalPark, Canada." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1556837847169027.
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Evans, Nicholas Philip. "Isotope systematics of gypsum and its hydration water." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/290136.
Full textAbstract:
Triple oxygen and hydrogen isotope analysis of the structurally-bound water in gypsum can provide a direct measure of past hydrologic variability. This thesis presents the development of the water extraction and isotopic measurement procedures, the calculation of the gypsum-water isotope fractionation factors, and the application of the method to constrain the palaeohydrologic conditions in two temporally and geographically disparate sites. Measurement of the isotopic composition of gypsum hydration water is used to examine the hydrological changes that occurred during the Terminal Classic Drought of the Maya lowlands (~800-1000 CE), coincident with the period when the Classic Maya Civilization of Mesoamerica collapsed. The data provide a complete and direct archive of hydrological conditions that have previously been limited to ice core records. Mean annual rainfall is shown to have decreased by between 41% and 54%, with intervals of up to 70%, compared to present-day conditions. This study has also shown for the first time that relative humidity was 2%-7% lower during the Terminal Classic Drought compared to today. The methodology is also applied to the massive gypsum deposits in the marginal and deep basins of the Mediterranean to interpret the chemical evolution of parent water bodies during the Messinian Salinity Crisis (5.97-5.3 Ma). By combining the measurement of gypsum hydration water with other traditional (e.g. strontium) and novel (e.g. calcium and barium) isotope tracers, the hydrological changes during the deposition of Primary Lower Gypsum units of the Sorbas Basin in southeastern Spain, the Upper Gypsum units of Sicily, and deep basin deposits have been constrained. The results indicate that all deposits experienced a significant freshwater contribution to the mother fluids from which they formed. It is proposed that obliquity-controlled sea level and eccentricity-modulated precession, superimposed on longer-term tectonic restriction of the Mediterranean-Atlantic exchange, together controlled the varying depositional environments during the formation of the Messinian Salt Giant. This thesis demonstrates that the analysis of gypsum hydration water is a powerful tool for palaeoclimate reconstruction. The methodology can be applied to gypsum (and other hydrated minerals) in a wide range of settings across geological space and time, providing a rich source of information about the environmental conditions under which they formed.
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Müller, Inigo Andreas [Verfasser], Wolfgang [Akademischer Betreuer] Bach, and Timothy G. [Akademischer Betreuer] Ferdelman. "The pivotal role of sulfite species in shaping the oxygen isotope composition of sulfate: new insights from a stable isotope perspective / Inigo Andreas Müller. Gutachter: Wolfgang Bach ; Timothy G. Ferdelman. Betreuer: Wolfgang Bach." Bremen : Staats- und Universitätsbibliothek Bremen, 2013. http://d-nb.info/1072076942/34.
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Dubbert, Maren [Verfasser], and Christiane [Akademischer Betreuer] Werner. "Water balance and productivity of a Mediterranean oak woodland: Quantifying understory vegetation impacts by development of a stable oxygen isotope partitioning approach / Maren Dubbert. Betreuer: Christiane Werner." Bayreuth : Universität Bayreuth, 2014. http://d-nb.info/1060010348/34.
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Labuhn, Inga. "Climate Variability in Southwest France During the Last 2000 Years : Proxy Calibration and Reconstruction of Drought Periods Based on Stable Isotope Records from Speleothems and Tree Rings." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01063541.
Full textAbstract:
The characterization of natural climate variability is important in order to understand the climate response to natural forcings and to identify anthropogenic influences. The aim of this thesis is to reconstruct climate changes in the southwest of France, a region which is characterised by recurrent drought periods, where high resolution proxy records of the last millennia were lacking.The reconstruction is based on multiple proxies from two continental archives: speleothems and tree rings. Their combination can make use of the strengths of each archive while compensating their weaknesses. There are two principal objectives: first, to gain a better understanding of the climatic and non-climatic influences on each proxy; and second, to reconstruct drought periods in the past.The oxygen isotopic composition (δ18O) of speleothem fluid inclusions and tree ring cellulose is controlled to a large extent by the δ18O of precipitation, which can serve as a tracer of the atmospheric circulation. In order to interpret these proxies in terms of climate, it is necessary to understand how the climate signal becomes recorded in the proxy, and which processes modify the original signal during the formation of the archive.Measurements of δ18O in precipitation, cave drip water, and fluid inclusions in modern speleothem samples from Villars Cave demonstrated that the isotopic composition of cave drip water corresponds to the pluri-annual average precipitation. The speleothem fluid inclusions, in turn, preserve the isotopic composition of the drip water. Based on this calibration, it is possible to reconstruct drip water isotope variability using fluid inclusions in a more than 2000 year old stalagmite, which has been dated by laminae counting, as well as U-Th and 14C measurements. Changes in the cave environment, e.g. the vegetation cover, are indicated by other proxies from the same stalagmite (stable isotopes in calcite and trace element concentrations), but these changes do not seem to impact the fluid inclusion δ18O significantly.The isotopic composition of tree ring cellulose from Quercus spp. in the study area is strongly influenced by climate conditions during the summer. However, non-climatic influences on the isotopic composition of cellulose are identified. They are linked to the age of the trees and to site hydrology, and must be accounted for in the sampling and analytical procedures. Crossdated cores from living trees and timber wood in historic buildings near Angoulême are used to build an annually resolved chronology of cellulose δ18O. Significant correlations with meteorological data enable a calibration and a reconstruction of drought periods since 1360 AD.Lastly, this thesis explores a novel approach of integrating oxygen isotope records from speleothem fluid inclusions and tree ring cellulose from closely located sites to reconstruct both high- and low-frequency variability of droughts in the past.
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Gregoricka, Lesley Ann. "Mobility, Exchange, and Tomb Membership in Bronze Age Arabia: A Biogeochemical Investigation." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1321290287.
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Espinoza, Pepe. "Trophic dynamics in the northern Humboldt Current system : insights from stable isotopes and stomach content analyses." Thesis, Brest, 2014. http://www.theses.fr/2014BRES0066/document.
Full textAbstract:
Le nord du système du Courant de Humboldt (NHCS), le long des côtes péruviennes, est l'une des régions océanique les plus productives au monde. Il représente moins de 0.1% de la surface des océans mondiaux mais contribue actuellement à plus de 10% des captures mondiales en poissons, avec l’anchois Engraulis ringens comme espèce emblématique. Comparé aux autres systèmes d’upwelling de bord Est, la forte productivité en poissons ne peut être expliquée par une productivité primaire plus élevée. Par contre, le NCHS est la région où El Niño, et la variabilité climatique en général est la plus notable. D’autre part, les eaux de surface oxygénées recouvrent une zone de minimum d’oxygène extrêmement intense et superficielle. L’objectif principal de ce travail est de mieux comprendre les relations trophiques au sein du NHCS en combinant l'analyse de contenus stomacaux et d'isotopes stables. Cette étude se focalise sur une variété d’organismes allant des bas niveaux trophiques comme le zooplancton aux prédateurs supérieurs (oiseaux et les otaries à fourrure). Elle combine des études de contenus stomacaux ponctuelles et sur le long terme d’espèces clés telles que l’anchois et la sardine Sardinops sagax et une analyse plus globale, basée sur l'utilisation d'isotopes stables et considérant l’ensemble du réseau trophique dans les années récentes (2008 – 2012). Les analyses des contenus stomacaux d'anchois et de sardine ont permis de revisiter l'écologie de ces espèces. En effet, bien que le phytoplancton domine largement les contenus stomacaux en termes d’abondance numérique, le zooplancton est de loin la composante alimentaire la plus importante pour ces deux espèces en termes de carbone. Dans le cas de l’anchois, les euphausiacés contribuent à plus de 67.5% du carbone ingéré, suivis par les copépodes (26.3%). Sélectionner les proies les plus grandes telles que les euphausiacés procure un avantage énergétique pour l’anchois dans cet écosystème où les carences en oxygène imposent de fortes contraintes métaboliques aux poissons pélagiques. La sardine se nourrit de zooplancton plus petit que l’anchois (copépodes plus petits et moins d’euphausiacés). Ainsi, la compétition trophique entre les sardines et les anchois est minimisée dans le NSCH par le partage de la ressource zooplancton selon sa taille, comme cela a déjà été montré dans d’autres écosystèmes. Ces résultats remettent en question la compréhension première de la position des petits poissons pélagiques (zooplanctonophage et non phytoplanctonophage) dans la chaine trophique ce qui implique de reconsidérer le fonctionnement et les modèles trophiques du NCHS. Afin d’obtenir une compréhension plus globale de la position trophique relative des principaux composants du NHCS une approche basée sur des analyses d’isotopes stables (δ13C et δ15N) a été utilisée. Pour ce faire, la signature isotopique d'échantillons de 13 groupes taxonomiques (zooplancton, poissons, calmars et prédateurs supérieurs) prélevés entre 2008 et 2011 a été déterminée. Les valeurs de δ15N obtenues sont fortement impactées par l’espèce, la taille et la latitude. Le long de la cote péruvienne, la zone de minimum d’oxygène devient en effet plus intense et plus superficielle au sud de ~7.5ºS impactant fortement la valeur de δ15N de la ligne de base. Nous avons donc utilisé un modèle linéaire à effet mixte prenant en compte les effets latitude et taille afin de prédire la position trophique relative des composants clés de l’écosystème. Ces analyses isotopiques confirment les résultats issus des contenus stomacaux sur le régime alimentaire de l’anchois et mettent en évidence l’importance potentielle d’une composante souvent négligée de l’écosystème, la galathée pélagique Pleuroncodes monodon. En effet, nos résultats supportent l’hypothèse selon laquelle cette espèce s’alimenterait en partie sur les oeufs et larves d’anchois, menaçant ainsi les premiers stades de vie des espèces exploitées. [...]The northern Humboldt Current system (NHCS) off Peru is one of the most productive world marine regions. It represents less than 0.1% of the world ocean surface but presently sustains about 10% of the world fish catch, with the Peruvian anchovy or anchoveta Engraulis ringens as emblematic fish resource. Compared with other eastern boundary upwelling systems, the higher fish productivity of the NHCS cannot be explained by a corresponding higher primary productivity. On another hand, the NHCS is the region where El Niño, and climate variability in general, is most notable. Also, surface oxygenated waters overlie an intense and extremely shallow Oxygen Minimum Zone (OMZ). In this context, the main objective of this study is to better understand the trophic flows in the NHCS using both stomach content and stable isotope analyses. The study focuses on a variety of organisms from low trophic levels such as zooplankton to top predators (seabirds and fur seals). The approach combines both long-term and specific studies on emblematic species such as anchoveta, and sardine Sardinops sagax and a more inclusive analysis considering the 'global' food web in the recent years (2008 –2012) using stable isotope analysis.Revisiting anchovy and sardine we show that whereas phytoplankton largely dominated anchoveta and sardine diets in terms of numerical abundance, the carbon content of prey items indicated that zooplankton was by far the most important dietary component. Indeed for anchovy euphausiids contributed 67.5% of dietary carbon, followed by copepods (26.3%).Selecting the largest prey, the euphausiids, provide an energetic advantage for anchoveta in its ecosystem where oxygen depletion imposes strong metabolic constrain to pelagic fish. Sardine feed on smaller zooplankton than do anchoveta, with sardine diet consisting of smaller copepods and fewer euphausiids than anchoveta diet. Hence, trophic competition between sardine and anchovy in the northern Humboldt Current system is minimized by their partitioning of the zooplankton food resource based on prey size, as has been reported in other systems.These results suggest an ecological role for pelagic fish that challenges previous understanding of their position in the foodweb (zooplanktophagous instead of phytophagous), the functioning and the trophic models of the NHCS.Finally to obtain a more comprehensive vision of the relative trophic position of NHCS main components we used stable isotope analyses. For that purpose we analyzed the δ13C and δ15N stable isotope values of thirteen taxonomic categories collected off Peru from 2008 - 2011, i.e., zooplankton, fish, squids and air-breathing top predators. The δ15N isotope signature was strongly impacted by the species, the body length and the latitude. Along the Peruvian coast, the OMZ get more intense and shallow south of ~7.5ºS impacting the baseline nitrogen stable isotopes. Employing a linear mixed-effects modelling approach taking into account the latitudinal and body length effects, we provide a new vision of the relative trophic position of key ecosystem components. Also we confirm stomach content-based results on anchoveta Engraulis ringens and highlight the potential remarkable importance of an often neglected ecosystem component, the squat lobster Pleuroncodes monodon. Indeed, our results support the hypothesis according to which this species forage to some extent on fish eggs and larvae and can thus predate on the first life stages of exploited species. However, the δ13C values of these two species suggest that anchoveta and squat lobster do not exactly share the same habitat. This would potentially reduce some direct competition and/or predation
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Kuiper, Yvette Dominique. "Isotopic constraints on timing of deformation and metamorphism in the Thor–Odin dome, Monashee Complex, southeastern British Columbia." Thesis, Department of Geology, University of New Brunswick, 2003. http://hdl.handle.net/1882/46.
Full textAbstract:
New and existing U–Pb and 40Ar/39Ar geochronological data, and oxygen and
hydrogen stable isotope data, are combined with structural and metamorphic data from Thor–Odin, the southern culmination of the Monashee Complex. This leads to a new interpretation of the timing of deformation and metamorphism. Amphibolites in Thor–Odin with hornblende 40Ar/39Ar dates between ~75–70 and ~51 Ma experienced more 18O- and D-depletion than amphibolites with older dates. The younger dates that were previously interpreted as cooling ages, may have resulted from complete or partial Ar loss in the presence of meteoric fluids that were introduced into the rock during extension.
Monazite crystals in pelitic schist, quartzite and orthogneiss, which have U–Pb ages younger than 40Ar/39Ar hornblende ages in amphibolite in northwest Thor–Odin, may have grown during tension in the presence of fluids. Titanite, xenotime and zircon dates may be interpreted in the same way. Thus, the U–Pb dates that were previously interpreted as representing peak of metamorphism and the hornblende 40Ar/39Ar dates that were previously interpreted as representing cooling ages, may be interpreted as reflecting meteoric fluid penetration of the crust during regional extension. This implies that the age of the thermal peak of metamorphism is older than ~75–70 Ma. Migmatisation in a basement orthogneiss in Thor–Odin occurred at ~1.8 Ga. Dissolution rims are preserved in zircon between ~1.8 Ga domains and 52 Ma overgrowths. Because growth of new zircon (and possibly other U–Pb accessory phases) did not take place, any geological event that occurred during the ~1.8 Ga to 52 Ma time interval is not recorded. Cordilleran deformation and metamorphism may have taken place within that time interval, e.g. in the Middle Jurassic and/or mid- to Late Cretaceous, the time of Cordilleran deformation and metamorphism in the rocks overlying the Monashee Complex.
The Joss Mountain orthogneiss, west of the Monashee Complex in the Selkirk Allochthon, is dated at 362 +/– 13 Ma. F3 folding in pelitic schist at Joss Mountain is constrained between ~73 and ~70 Ma. Existing structural, metamorphic and geochronological data in, and close to, the Shuswap Metamorphic Complex in the southern Canadian Cordillera are shown to be consistent with a channel flow model.
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Jansen, Kirstin. "Stable Isotopes and Metabolite Profiles as Physiological Markers for the Drought Stress Sensitivity in Douglas-Fir Provenances (Pseudotsuga menziesii (MIRB.) FRANCO)." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19617.
Full textAbstract:
In Mitteleuropa werden zukünftig häufigere Trocken- und Hitzeperioden mit wirtschaftlichen Einbußen in der Waldwirtschaft erwartet. Die Douglasie (Pseudotsuga menziesii (Mirb.) Franco) wird als Alternative für die wirtschaftlich bedeutsame, jedoch trockenheitsempfindliche Fichte diskutiert (Picea abies (L.) H.Karst.). Zwei Unterarten, die Küsten- (FDC) und die Inlandsdouglasie (FDI), sind im ausgedehnten natürlichen Verbreitungsgebiet in Nordamerika beheimatet, welches ein großes Potenzial für die Auswahl produktiver und trockenresistenter Herkünfte bietet. Unser Ziel war, die Trockenreaktion verschiedener Douglasienherkünfte unter Verknüpfung morphologischer und physiologischer Parameter und die der Trockenheitsresistenz bzw. -empfindlichkeit zugrundeliegenden Mechanismen zu erforschen. Ein Herkunftsversuch in Südwestdeutschland ermöglichte die Untersuchung 50-jähriger Douglasien verschiedener Herkünfte entlang eines Höhengradienten. Unter kontrollierten Bedingungen simulierten wir die Effekte einer Hitzewelle auf Jungbäume zweier Provenienzen. Wir analysierten die Kohlenstoff- und Sauerstoff-Stabilisotopenzusammensetzung, den Gaswechsel der Blätter, Veränderungen im Stoffwechsel und das Baumwachstum.
Unsere Ergebnisse zeigen bei FDC aus humiden Regionen hohe Wachstumseinbußen unter Trockenheit und moderat bis stark verringerte stomatäre Leitfähigkeit, unterstützt durch Photoprotektion. FDC aus Regionen mit starker Sommertrockenheit reagierten kaum mit Stomataschluss und Wachstumseinbußen auf Trockenheit, jedoch mit starker Osmoregulation und Monoterpen-Emissionen, welche zur Trockenresistenz beitragen könnten. FDI aus einer ariden Region zeigten hohe An, geringes Wachstum und stark antioxidative und photoprotektive Mechanismen.
Die Herkünfte unterscheiden sich stark in ihrer Trockenreaktion und ihren Schutzmechanismen. Der Anbau trockenresistenter Herkünfte wird an Standorten von Vorteil sein, für die eine Häufung von ariden Sommerperioden vorhergesagt wird.In Central Europe, more frequent periods of dry and hot weather are expected in the future with economic losses in the forestry sector. Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) is discussed as a timber species alternative to the economically important but drought-sensitive spruce (Picea abies (L.) H. Karst.). Two subspecies, the coastal (FDC) and the interior Douglas-fir (FDI), are native to an extensive natural range in North America, offering a great potential for the selection of productive and drought tolerant provenances. Our goal was to investigate the drought response of different Douglas-fir provenances on the morphological and physiological level, as well as the mechanisms underlying drought resistance or susceptibility. A provenance trial in southwestern Germany established in 1958 allowed the study of 50-year-old Douglas-fir trees of diverse provenances along a height gradient. Under controlled conditions, we simulated the effects of a heat wave on young trees of two provenances. We analyzed carbon and oxygen stable isotopic composition, leaf gas exchange, changes in metabolism and tree growth. FDC from humid regions responded to drought with strong growth decline and a medium to strong stomatal closure, supported by enhanced instantaneous photoprotection. FDC from regions with very dry summer conditions showed a small growth decline and anisohydric regulation of stomatal conductance under drought, supported by high levels of osmotic adjustment. High monoterpene emissions might contribute to the drought resistance. FDI from an arid region showed high assimilation rates, low growth potential and a high antioxidant, photoprotective, drought and heat protective potential. The provenances differ greatly in their dry reaction and their protective mechanisms. The cultivation of drought resistant crops will be beneficial at sites predicted to accumulate arid summer periods.
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Wellman, Toby. "Carbon and oxygen stable isotopes from recent and fossil Australian crustaceans /." Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09SB/09sbw4528.pdf.
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Mutchler, Scott R. "Oxygen stable isotopic analysis of calcite by Raman microprobe spectrometry." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-05092009-040655/.
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Warrington, Anita Glasgow. "Stable isotopes of carbon and oxygen in the shells of terrestrial molluscs." Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316976.
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Harwood, Kirsty. "Variation in the stable isotopes of oxygen and carbon within forest canopies." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360330.
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Brown, James E. "Ion Microprobe δ18O-contraints on Fluid Mobility and Thermal Structure During Early Slip on a Low-angle Normal Fault, Chemehuevi Mountains, SE California." Ohio University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1448361194.
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ZNEIMER, STEPHANIA. "Stable isotopic composition of southern Illinois precipitation from (2012-2017) summary." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2578.
Full textAbstract:
This study examines variability in the isotopic composition of precipitation in southern Illinois, USA using a 5-year, event-based record, novel in its duration and in potential to extract important isotopic information of precipitation in a dynamic region, and the seasonality of major moisture sources. The isotopic composition of precipitation exhibited seasonal variations in δ18O and δ2H, where values are distinctively higher (lower) during summer (winter). Average values for d-excess were the highest (lowest) during autumn (summer). Seasonality is also present in events originating from the Gulf of Mexico (GOM), isolated by Langrangian methods. GOM JJA events showed more isotopically depleted precipitation than of non-GOM events due to a stronger “amount effect” signal (R2 = -0.40). To date, the amount effect has never been reported this far inland in the US. Precipitation analysis as it related to the ENSO phases exhibited statically significant differences in d-excess values. Precipitation events that occurred during a La Niña phase exhibited positive d¬-excess values, with an average value of 25.18‰. δ18O and δ2H values during El Niño phase were on average more depleted. Overall results highlight that the GOM, as a dominating moisture source, and ENSO phases can modulate the seasonal and intra-seasonal variability in the isotopic composition of precipitation in this region. The data collected, from a single location, can highlight moisture dynamics occurring on a regional scale and highlight the importance of the GOM as prevailing source of moisture for the Midwestern US. The second part of this study involved determining what were the best predictors for 18O and d-excess values. The study revealed that sea surface temperature and oxygen isotope values in the ambient vapor were the best predictors for 18O values but were the poorest predictors of d-excess values. The best predictors of d-excess were land surface characteristics such as the volumetric soil moisture, evaporation from bare soil variable, as well as SST, temperature of the air and specific humidity of the air. However, these predictors worked best with positive d-excess values that equaled or above 20‰.
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Stephenson, Richard Javier. "Tropical land snails as precipitation proxies: Oxygen stable isotopes of shells from Trinidad Island." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563273765452653.
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Duffy, Margaret R. "Determining the biological turnover rate of phosphate in agricultural soils using stable oxygen isotopes." Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1593864445251739.
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Woodley, Ewan James. "Reconstructing the climate of Scotland using stable carbon and oxygen isotopes in tree-rings." Thesis, Swansea University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678326.
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Robbins, John A. "Stable isotopes, marine paleoclimates, and human subsistence on California's Channel Islands." Ann Arbor, Mich. : ProQuest, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1442835.
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Thesis (M.S. in Geology)--S.M.U., 2007.Title from PDF title page (viewed Mar. 18, 2008). Source: Masters Abstracts International, Volume: 45-05, page: 2387. Adviser: Robert Gregory. Includes bibliographical references.
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Winhusen, Eric. "PRECAMBRIAN SEAWATER TEMPERATURE ANALYSIS USING OXYGEN ISOTOPES FROM HAMERSLEY CARBONATES, WESTERN AUSTRALIA." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin992268720.
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Brooks-English, Nathanael Talman. "Stable Isotopes in the Spines of Columnar Cactus: a New Proxy for Climate and Ecophysiological Research." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195268.
Full textAbstract:
There are relatively few annually resolved climate proxies in arid and semi-arid regions. Columnar cactuses are common in these regions and the stable isotopes of carbon and oxygen in durable spines record variations in rainfall, humidity and ecophysiology as they grow in series along the sides of cactuses. Despite their spines, columnar cactuses provide important ecosystem resources and services in drought prone areas, however, the impact that long-term climate variability and infrequent storms (El Niño or tropical storms) have on the ecology and ecophysiology of columnar cactus is less clear. Stable isotopes in trees and corals serve as useful proxies of climate and ecophysiological information, but for cactus we lack the most rudimentary information about the isotopic systems and their links to the environment. Here, we present an isotopic framework that begins with developing semi-empirical mechanistic models of δ¹³C, δ¹⁸O and δ²H variation in saguaro cactuses that link physical and physiological fractionation factors in stem water and spines to rainfall and humidity. We also review a novel method for determining the age of spines, an important step in developing useful chronologies of isotopic variation in spines. The mechanistic models combined with local climate records enhance our understanding of isotopic variation in daily and annually dated spine δ¹³C and δ¹⁸O records and explain the statistical association of δ¹³C and δ¹⁸O in spines with rainfall, vapor pressure deficit, and El Niño enhanced winter rains. While there are still some challenges to overcome, we expect that isotopic spine series will be used as climate proxies to answer questions regarding regional climate variability or to enhance current models of past and future climates. Likewise, ecophysiologists can use the isotopic spine series in conjunction with gas exchange or carbohydrate studies to look at reproductive or biological responses to changing environments.
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Barger, Erin E. "Migration of Recharge Water Downgradient from the Santa Catalina Mountains into the Tucson Basin Aquifer." Thesis, The University of Arizona, 1996. http://hdl.handle.net/10150/249235.
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Aquifers in the arid alluvial basins of the southwestern U.S. are recharged predominantly by infiltration from streams within the basins and by water entering along the margins of the basins from surrounding mountains (mountain -front recharge). The Tucson Basin of Southeastern Arizona is such a basin. The Santa Catalina Mountains form the northern boundary of this basin and receive more than twice as much precipitation (about 70 cm/yr) as the basin does (about 30 cm/yr). In this study environmental isotopes were employed to investigate the migration of precipitation basinward through joints and fractures. Water samples were obtained from springs in the Santa Catalina Mountains. Stable isotopes and thermonuclear bomb-produced tritium enabled qualitative characterizations of flow paths and flow velocities. Stable isotopic measurements fail to display a direct altitude effect. Tritium values indicate that although a few springs discharge pre-bomb water, most springs discharge waters from the 1960's or later.
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Bantelmann, Eva. "Biosphere-Atmosphere CO₂ exchange in a mountainous grassland ecosystem investigated with stable carbon and oxygen isotopes /." Zürich : ETH, 2006. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16656.
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