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Literatura académica sobre el tema "Mid-Pleistocene transition"

Autor: Grafiati

Publicado: 4 de junio de 2021

Última modificación: 27 de abril de 2022

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Artículos de revistas sobre el tema "Mid-Pleistocene transition"

Huybers, P. "Pleistocene glacial variability as a chaotic response to obliquity forcing". Climate of the Past Discussions 5, n.º 1 (21 de enero de 2009): 237–50. http://dx.doi.org/10.5194/cpd-5-237-2009.

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Abstract. The mid-Pleistocene transition from 40 ky to ~100 ky glacial cycles is generally characterized as a singular transition attributable to scouring of continental regolith or a long-term decrease in atmospheric CO2 concentrations. Here an alternative hypothesis is suggested, that Pleistocene glacial variability is chaotic and that transitions from 40 ky to ~100 ky modes of variability occur spontaneously. This alternate view is consistent with the presence of ~80 ky glacial cycles during the early Pleistocene and the lack of evidence for a change in climate forcing during the mid-Pleistocene. A simple model illustrates this chaotic scenario. When forced at a 40 ky period the model chaotically transition between small 40 ky glacial cycles and larger 80 and 120 ky cycles which, on average, give the ~100 ky variability.

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Huybers, P. "Pleistocene glacial variability as a chaotic response to obliquity forcing". Climate of the Past 5, n.º 3 (3 de septiembre de 2009): 481–88. http://dx.doi.org/10.5194/cp-5-481-2009.

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Abstract. The mid-Pleistocene Transition from 40 ky to ~100 ky glacial cycles is generally characterized as a singular transition attributable to scouring of continental regolith or a long-term decrease in atmospheric CO2 concentrations. Here an alternative hypothesis is suggested, that Pleistocene glacial variability is chaotic and that transitions from 40 ky to ~100 ky modes of variability occur spontaneously. This alternate view is consistent with the presence of ~80 ky glacial cycles during the early Pleistocene and the lack of evidence for a change in climate forcing during the mid-Pleistocene. A simple model illustrates this chaotic scenario. When forced at a 40 ky period the model chaotically transitions between small 40 ky glacial cycles and larger 80 and 120 ky cycles which, on average, give the ~100 ky variability.

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Maasch, KA. "Statistical detection of the mid-Pleistocene transition". Climate Dynamics 2, n.º 3 (febrero de 1988): 133–43. http://dx.doi.org/10.1007/bf01053471.

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Ao, Hong, Eelco J. Rohling, Chris Stringer, Andrew P. Roberts, Mark J. Dekkers, Guillaume Dupont-Nivet, Jimin Yu et al. "Two-stage mid-Brunhes climate transition and mid-Pleistocene human diversification". Earth-Science Reviews 210 (noviembre de 2020): 103354. http://dx.doi.org/10.1016/j.earscirev.2020.103354.

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Bowler, Jim M. y Mike Sandiford. "Dynamic Antarctic Ice: Agent for Mid-Pleistocene Transition". PAGES news 15, n.º 2 (octubre de 2007): 16–18. http://dx.doi.org/10.22498/pages.15.2.16.

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Tabor, Clay R. y Christopher J. Poulsen. "Simulating the mid-Pleistocene transition through regolith removal". Earth and Planetary Science Letters 434 (enero de 2016): 231–40. http://dx.doi.org/10.1016/j.epsl.2015.11.034.

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Medina-Elizalde, M. "The Mid-Pleistocene Transition in the Tropical Pacific". Science 310, n.º 5750 (11 de noviembre de 2005): 1009–12. http://dx.doi.org/10.1126/science.1115933.

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WANG, Ting, YouBin SUN y XingXing LIU. "Mid-Pleistocene climate transition: Characteristic, mechanism and perspective". Chinese Science Bulletin 62, n.º 33 (1 de noviembre de 2017): 3861–72. http://dx.doi.org/10.1360/n972017-00427.

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Diester-Haass, Liselotte, Katharina Billups y Caroline Lear. "Productivity changes across the mid-Pleistocene climate transition". Earth-Science Reviews 179 (abril de 2018): 372–91. http://dx.doi.org/10.1016/j.earscirev.2018.02.016.

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Deblonde, G. y W. R. Peltier. "A Paleoclimatic Model of the Mid-Pleistocene Climate Transition". Annals of Glaciology 14 (1990): 47–50. http://dx.doi.org/10.1017/s0260305500008247.

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A one-dimensional time-dependent ice-sheet model is employed to simulate ice-volume variations throughout the Pleistocene epoch of Earth history. The model is based upon the explicitly-described physics of ice-sheet accumulation and flow and the physics of the viscoeleastic relaxation of the Earth under the weight of the ice load. The model of the viscoelastic relaxation of the Earth incorporates the vertical variation of density and viscosity of its interior in great detail. An abrupt variation of some of the parameters that govern the height of the ice-sheet equilibrium line, and a gradual increase in the strength of a generalized feedback mechanism that is turned on after mid-Pleistocene time, lead to simulation of ice volume that has the general features of observed δ18O records, in particular the new high-resolution oxygen-isotope record from site ODP 677 (Peltier and others, 1989).

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Tesis sobre el tema "Mid-Pleistocene transition"

Russon, Thomas Ford. "Paleoceanography of the southern Coral Sea across the Mid-Pleistocene Transition". Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/4876.

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A comprehensive theory explaining the relationship between periodic variations in the Earths orbital parameters and the response of the climate system remains elusive. One of the key challenges is that of the Mid-Pleistocene Transition (MPT), during which the dominant mode of glacial/interglacial climatic variability shifted without any corresponding change in the mode of orbital forcing. Subtropical climate on orbital time-scales is sensitive to variability in both the low-latitude ocean/atmosphere circulation regime and the global carbon-cycle (through its effect on atmospheric greenhouse gas levels), both of which may have played a role in the shift in mode of global climate response to orbital forcing during the MPT. This thesis presents a series of multi-proxy (foraminiferal stable isotope and trace-metal) paleoceanographic reconstructions from the subtropical southwest Pacific, as seen in marine sediment core MD06-3018, from 2470m water depth and 23ºS in the New Caledonia Trough, southern Coral Sea. The core age-model, based upon magnetic stratigraphy and orbital tuning, yields a mean sedimentation rate at the site of 20mm/ka and a core-bottom age of 1600ka. The MD06-3018 reconstruction of New Caledonia Trough deep water chemistry, based on benthic 13C measurements, shows that the spatial chemistry gradient within the Southern Ocean between deep waters entering the Tasman Sea and the open Pacific was greater during glacial (relative to interglacial) stages over at least the past 1100ka. This gradient was, however, generally reduced on the >100kyr time-scale across the MPT, consistent with it being a period of reduced deep water ventilation in both hemispheres. The MD06-3018 Mg/Ca-derived reconstruction of subtropical southwest Pacific Sea Surface Temperature (SST) shows glacial/interglacial variability of 2-3ºC but no significant trends on the >100kyr time-scale over the duration of the record. An estimate of the uncertainty associated with the SST reconstruction demonstrates that no significant changes in reconstructed southern Coral Sea mean-annual SST can be identified between interglacial stages across the MPT. It is, therefore, unlikely that regional climatic change constituted the main cause for the observed middle Pleistocene expansion of coral reef systems. The >100kyr time-scale stability of southern Coral Sea SST means that the position of the southern boundary of the Pacific warm pool has also been stable over at least the past 1500ka. Comparison with other low-latitude Pacific reconstructions shows that the early Pleistocene warm pool was consequently more hemispherically asymmetric than its present configuration, with the latter being established by ~1000ka and implying significant changes in meridional atmospheric heat and moisture fluxes prior to the MPT. On orbital time-scales, the SST reconstruction shows a clear shift from dominant 40kyr to 100kyr modes of variability over the MPT, although significant 40kyr structure is also retained into the middle/late Pleistocene. In contrast, reconstructed hydrological cycle variability (based on coupled 18O-Mg/Ca measurements) shows only limited coherence with the obliquity cycle and a stronger relationship with the precession cycle. The decoupling of the reconstructed subtropical SST and hydrological cycle responses places constraints on the extent of orbitally paced fluctuations in the low-latitude ocean/atmosphere system. Instead, comparison of the MD06-3018 SST reconstruction with others from across the lowlatitude Pacific supports a dominant role for greenhouse gas forcing in low-latitude western Pacific glacial/interglacial SST variability across the Pleistocene. The subtropical multi-proxy climate reconstructions presented here show that the timing and sense of long-term (>100kyr time-scale) changes in the low-latitude ocean/atmosphere circulation regime are consistent with that system having been important in the expansion of northern hemisphere ice-volume during the early part of the MPT. However, the subtropical reconstructions also suggest that neither the low-latitude ocean/atmosphere circulation system nor the global carbon-cycle underwent a fundamental change in mode of response to orbital forcing during the transition. Instead, the origin of the 100kyr glacial/interglacial mode was most likely related to thresholds in the dynamics of the expanding northern hemisphere icesheets, leading in turn to the existence of significant inter-hemispheric asymmetry in the orbital time-scale climate response over the middle/late Pleistocene. Summary for Non-Specialists. Over the past five million years of its history, the Earths climate has undergone a series of regular, or nearly regular, fluctuations between warmer and colder states. These fluctuations take tens to hundreds of thousands of years to occur and are known as the ‘glacial/interglacial cycles’ on account of the associated changes in ice-sheet extent in the high-latitudes. The origin of these cycles is widely held to be the regular variations in form of the Earths orbit around the sun. In spite of decades of research, however, no complete ‘orbital theory of climate’ exists, mainly because the patterns of past climate variability, as reconstructed using ‘proxies’ for variables such as surface temperature, is much more complex than that of the orbital variations themselves. It follows that processes within the Earth system, especially those associated with large ice-sheets, the carbon-cycle and the ocean circulation system, act to substantially modify the climate response to the orbital variations. Over the past ten years, new observations from both ice-cores and low-latitude marine sediment cores have suggested that the dominant system(s) involved in setting the Earths response to the orbital variations may potentially be the carboncycle and/or the low-latitude ocean/atmosphere circulation regime rather than highlatitude ice-sheet dynamics, as was generally supposed previously. If this new view is correct, it has profound implications for the general sensitivity of the climate to the carbon-cycle on a range of time-scales - making its evaluation a scientific objective of considerable current importance. This thesis presents a series of reconstructions of aspects of climate and carbon-cycle variability for the subtropical southwest Pacific, as based on proxy measurements in a marine sediment core than spans the past 1,600,000 years at around 5000 year resolution. The key focus is on an interval called the ‘Mid- Pleistocene Transition’, during which time the mode of glacial/interglacial variability changed, indicating a fundamental change in one or more aspects of the response to the orbital forcing. The study site is well placed to investigate variability in both the carbon-cycle and low-latitude ocean circulation over the climatic transition as it lies between the Southern Ocean, a key source of carbon-cycle variability and the equatorial Pacific, where the modern El-Niño system arises. By characterizing variability in these systems, the potential role played by both systems in causing the change in mode of glacial/interglacial variability can be evaluated. The key findings of the thesis are that; firstly, changes in the long-term state of the low-latitude ocean circulation system may well have been important for the expansion of northern hemisphere ice-sheets during the early part of the Mid- Pleistocene Transition. Secondly, it provides further support for a close connection between variability in the carbon-cycle and low-latitude climate on orbital timescales but suggests that there is no clear evidence for either system undergoing a fundamental change in sensitivity to the orbital forcing during the transition.

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McClymont, Erin Louise. "Surface ocean circulation and organic carbon export across the mid-Pleistocene climate transition". Thesis, Durham University, 2004. http://etheses.dur.ac.uk/3129/.

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The mid-Pleistocene climate transition (MPT) marks a change in the nature of the climate system response to external forcing by insolation. This is represented first by the expansion of the northern hemisphere ice-sheets ca. 920 ka, and the emergence and dominance of glacial-interglacial oscillations with a 100-kyr period by 640 ka. The principal aim of this thesis is to understand the role of surface ocean circulation systems in the Atlantic and tropical Pacific and the strength of the biological carbon pump as drivers of the MPT. These two systems are examined as they exert important influences over global climate change through their impacts on heat and moisture transports, and carbon cycling and atmospheric CO2 concentrations. The robustness of the alkenone-derived U(^K)(_37') index for reconstructing past sea-surface temperatures (SSTs) during the mid-Pleistocene is confirmed. It is shown that the index is insensitive to changes in the alkenone source organisms, the Prymnesiophytes, has minimal impact on the relationship between and SST. Reconstructions of SSTs from the mid-high latitudes of the Atlantic Ocean and the tropical Pacific Ocean between 1500-500 ka reveal that a synchronous and global drop in surface ocean temperatures of more than 1oC occurred ca.1145 ka (from Marine Isotope Stage, MIS, 34). The global cooling is coincidental with a shift toward a 'La Nina'-state of atmospheric circulation within the tropical Pacific. By analogy with the modem climate system, this intensification of atmospheric circulation in the tropical Pacific would have reduced the flux of heat to the high northern latitudes. It is proposed that this development of a cooler global climate system eventually drove the mid-Pleistocene expansion of the northern hemisphere ice-sheets. However, the global cooling was accompanied by asynchronous expansion of sea-ice cover in the North Atlantic and North Pacific that reached its maximum extent ca. 990 ka. It is proposed that this initially limited the supply of moisture to the ice-sheet source regions. Thus, ice-sheet response lags the onset of the global cooling by nearly 300-kyr, occurring between 920 and 880 ka (MIS 22). The driving mechanism for the global cooling remains unclear, but may be related to a long-term decline in deep-water temperatures. It is accompanied by an increase in the export of organic carbon to the ocean floor at a global scale. This is interpreted to reflect a strengthening of the biological carbon pump, which may have maintained or even driven the cooling trend by drawing down atmospheric CO2 concentrations.

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Nicholl, Joseph Anthony Leo. "Changes in ice sheet dynamics across the mid-Pleistocene transition recorded in North Atlantic sediments". Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648858.

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Weirauch, Daniel R. "A high-resolution record of climate instability spanning ~1.0 million years across the mid-Pleistocene transition". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 131 p, 2007. http://proquest.umi.com/pqdweb?did=1472642111&sid=21&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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Peral, Marion. "Calibration of the clumped-isotope thermometer in foraminifera and its application to paleoclimatic reconstructions of the mid-Pleistocene in the Gulf of Taranto". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS382/document.

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Quantifier les variations de température océanique du passé est nécessaire pour comprendre les mécanismes qui régissent l’évolution climatique. Les méthodes de paléo-thermométrie classiques peuvent souffrir de limitation inhérente à l’écologie des organismes et/ou à cause de l’influence d'effets physico-chimiques (salinité, acidité de l’eau de mer…). Ce travail se focalise sur la technique de paléothermométrie Δ47, qui repose sur la mesure du « clumping isotopique » dans les carbonates. Il vise d’abord à établir une calibration appliquée aux foraminifères et ensuite à mettre en œuvre cette calibration pour l’étude des variations climatiques au cours de la transition du Pléistocène moyen (MPT). Notre calibration Δ47-température des foraminifères planctoniques et benthiques, prélevés dans des sédiments modernes, couvre une gamme de température de -2 à 25°C. Les valeurs de Δ47 sur 9 espèces de foraminifères présentent une excellente corrélation avec la température de calcification des organismes, estimée à partir des mesures isotopiques de l’oxygène. Les résultats obtenus confirment l’absence d’effets liés à l’écologie des foraminifères (effets vitaux et de taille des organismes) et démontrent que la salinité n’affecte pas les mesures de Δ47. Cette étude constitue une avancée méthodologique importante pour les futures études paléocéanographiques sur les foraminifères. La MPT correspond à une transition climatique marquée par un changement de fréquence des cycles glaciaires-interglaciaires (de 41 000 à 100 000 ans). La compréhension de cette période est un enjeu scientifique majeur pour appréhender la mise en place du climat actuel. Notre calibration Δ47-température a permis de quantifier les variations de températures au cours de la MPT en mer méditerranée (Section de Montalbano Jonico, sud de l’Italie) et particulièrement des stades isotopiques marins 31 et 19, considérés comme des analogues à l’Holocène. Les résultats indiquent que (i) les températures (Δ47) obtenues sont en adéquation avec les températures obtenues par d’autres paléothermomètres, (2) les températures permettent de retracer les changements de régime océanographique et hydrologique, et (3) la mesure du Δ47 est complément prometteur pour les études multi-méthodes en paléocéanographie
The quantification of past oceanic temperature changes is a critical requirement for understanding the mechanisms which regulate climate variations. Classical methods of paleothermometry could suffer from well-known limitations related to ecology and/or to physico-chemical biases (sea water salinity, acidity…). This work focuses on clumped-isotope carbonate thermometry (Δ47). It aims to establish a calibration of Δ47 foraminifera and use it to study past climatic variations through the Mid-Pleistocene Transition (MPT). Our Δ47 calibration in planktonic and benthic foraminifera collected from modern marine sediment covers a temperature range of -2 to 25 °C. The clumped-isotope compositions of 9 species of foraminifera show a robust correlation with the calcification temperature, estimated from the measurements of oxygen-18. These results confirm the absence of bias linked to foraminifer ecology (species-specific and foraminifer size effects) and provide evidence that salinity does not affect the Δ47 thermometer. This study constitutes significant methodological progress for future paleoceanographic applications in foraminifera.The MPT is a climatic transition characterized by a shift in the frequencies of glacial-interglacial cycles (from 41 000 to 100 000 years). Understanding the MPT is a major scientific objective, which underlies our effort to study the establishment of our present climate. Our Δ47 calibration was used to quantify temperature changes through the MPT in the Mediterranea Sea (Montalbano Jonico section, south of Italy), and in particular the marine isotopic stages 31 and 19, which may be described as Holocene analogues. We find that (1) Δ47 temperatures are in good agreement with temperatures reconstructed from other paleothermometers, (2) these results allow reconstructing changes in past oceanographic and hydrologic regime, and (3) Δ47 measurement are a promising component of multi-proxy paleoceanographic studies

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Ortolan, Riccardo. "Stratigrafia paleobiologica a macroinvertebrati marini nel Pleistocene inferiore-medio di Montalbano Jonico (Basilicata)". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24940/.

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La tesi analizza le dinamiche a macroinvertebrati bentonici marini lungo la “Sezione Ideale” di Montalbano Jonico (Matera) che era stata candidata a GSSP per il Pleistocene medio. Obiettivo è quello determinare se le associazioni a molluschi avessero risposto alle dinamiche glaciale interglaciale, individuate dagli isotopi stabili dell’ossigeno, anche in contesti relativamente profondi. Unendo tutti i dati raccolti è stato possibile affermare che le associazioni a macroinvertebrati bentonici abbiano risposto alle variazioni climatiche e hanno permesso di quantificare le oscillazioni del livello marino alla scala glaciale interglaciale. Inoltre, analizzando i depositi messisi in posto durante il MIS 19, sono state ricostruite delle oscillazioni a scala sub-milankoviana. Questo ha permesso di constatare che negli stadiali del MIS 19a siano documentate delle associazioni a macroinvertebrati bentonici con strutture tassonomiche simili a quelle rinvenute nel MIS 20. Le evidenze raccolte ci permettono di affermare che alla scala della ciclicità climatica di 104-5 anni il turnover faunistico sia associabile alle variazioni batimetriche, ad una scala a più alta frequenza (103-4 anni), il turnover sia invece maggiormente influenzato dalla stabilità dei parametri ambientali che contraddistinguono gli ambienti deposizionali campionati. Nel dettaglio periodi glaciali e stadiali del MIS 19a, sono caratterizzati da associazioni dominate da Ditrupa che indicata instabilità legata ad apporti sedimentari e/o torbidità dell’acqua. Mentre, periodi di interstadiali e interglaciali presentano depositi caratterizzati da associazioni dominate da Tritia e Alvania che testimoniano contesti di piattaforma esterna e ridotti apporti terrigeni. In conclusione, l’analisi delle associazioni a macroinvertebrati marini ha permesso di identificare i principali “driver” ambientali del turnover faunistico a diverse scale temporali e ricostruire le dinamiche paleoambientali lungo la Sezione Ideale.

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Tan, Ning. "Comprendre l’évolution de la cryosphère et du climat du Pliocène à la transition Plio-Pléistocène". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLV032/document.

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Cette thèse est consacrée à l’étude de l’interaction cryosphère-climat depuis le milieu du Pliocène jusqu’au quaternaire pendant l’installation pérenne de la calotte groenlandaise. Nous étudions d’abord les causes du développement et de la disparition de l’importante mais courte glaciation qui a eu lieu pendant le stade isotopique marin M2 (MIS M23.264-¬3.312 Ma). Ensuite, dans le cadre du programme international sur la modélisation du Pliocène (PLIOMIP2), nous étudions le climat de la période chaude du Plaisancien moyen(MPWP, 3.3-3.0Ma). Enfin, la troisième période étudiée est la transition Plio-Pléistocène transition (PPT, 3.0-2.5Ma), que nous avons étudiée grâce à un couplage asynchrone entre un modèle de climat et un modèle de calotte. A travers ces différentes périodes, nous avons amélioré la connaissance des relations entrepCO2, tectonique et climat pendant la transition d’un monde chaud et riche en CO2 vers le monde bien plus froid et à faible pCO2 des glaciations quaternaires. Ce résultat montre l’importance de mieux comprendre les relations entre dynamique océanique, pCO2 et climat
This thesis is devoted tounderstanding the interaction betweencryosphere and climate from the mid Plioceneto the early Quaternary during the onset ofNorthern Hemisphere Glaciation (NHG).Firstly, we investigate the causes for thedevelopment and decay of the large but shortliving glaciation that occurred during MarineIsotope Stage 2 (M2, 3.264-¬3.312 Ma);Secondly, in the framework of the internationalPliocene Model Intercomparison Project(PLIOMIP2), we study the climate of Mid-Piacenzian Warm Period (MPWP, 3.3-3.0Ma).Thirdly, we explore the Plio-PleistoceneTransition (PPT, 3.0-2.5Ma) with anappropriate asynchronously coupled climatecryosphere model. Through these differentperiods, we provide a better understanding ofthe relationship between pCO2, tectonics andclimat during the transition from a warm andhigh-CO2 world to the cold and low-CO2Quaternary glaciations. This work also pointsout the necessity to further study the linkbetween ocean dynamics, carbon cycle andclimate

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Caley, Thibaut. "De l'importance de l'Océan Indien pour les paléoclimats quaternaires : la mousson et le courant des Aiguilles". Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14331/document.

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L’océan Indien est le lieu de processus atmosphériques et océaniques majeurs dont les répercussions en terme climatique peuvent être de grandes importances. Cette thèse se propose de documenter les forçages, les variabilités, les impacts et les interactions de la mousson Indo-asiatique et du courant des Aiguilles à l’échelle orbitale (incluant les conditions glaciaires-interglaciaires) au cours de la période Quaternaire.Si le maximum d’insolation (minimum de précession et maximum d’obliquité) initie les fortes moussons Indo-asiatiques, des forçages internes au système climatique jouent également un rôle majeur pour expliquer leur dynamique (fort vents et précipitations), en particulier le changement de volume de glace de l’hémisphère Nord et l’export de chaleur latente de l’océan Indien Sud. La prédominance de ces forçages internes est propre à la mousson Indo-asiatique et la distingue des moussons boréales Africaines. Ceci indique que le concept de mousson globale n’est pas valable à l’échelle orbitale.Concernant l’hémisphère Sud, les variations de température de surface du courant des Aiguilles exercent un contrôle important sur le climat Sud Africain (la végétation et les précipitations). Ce courant permet également le transfert plus ou moins important de chaleur et de sel vers l’océan Atlantique Sud par l’intermédiaire de la migration de la convergence subtropicale et des vents d’ouest associés. Ce mécanisme, contrôlé fortement par la dynamique des hautes latitudes Sud, affecte la circulation thermo-haline globale et constitue un acteur important des transitions glaciaires-interglaciaires et des changements de mode de variabilité climatique au cours du Quaternaire (Transition Mid-Pleistocène et évènement du Mid-Brunhes). Les changements induits dans le climat de l’Hémisphère Nord, et notamment le volume de glace, pourraient ensuite se répercuter sur la dynamique de la mousson. En revanche, l’effet des moussons sur le courant des Aiguilles parait mineur. Toutefois, les interactions entre la mousson Indo-asiatique, l’ENSO et les éventuels IOD (dipôles climatiques de l’océan Indien) pourraient affecter la dynamique du courant
The Indian Ocean is the place of major atmospheric and oceanic processes with large potential repercussions on the global climatic system. This thesis investigates forcing, variations, impacts and interactions of the Indo-Asian monsoon and of the Agulhas current at the orbital scale (including glacial-interglacial conditions) over the Quaternary period.Insolation maximum (precession minimum and obliquity maximum) initiates strong Indo-Asian monsoons, but processes internal to the climate system, in particular Northern Hemisphere (NH) ice volume changes and the latent heat export of the south Indian Ocean, play a major role to explain their dynamics (strongest winds and precipitation). The predominance of these internal forcings is a specificity of the Indo-Asian monsoon and distinguishes it from African boreal monsoons. This indicates that the concept of a global monsoon at the orbital scale is a misnomer.Concerning the Southern hemisphere, sea surface temperature variations of the Agulhas current exert an important control upon the South African climate (vegetation and precipitation). This current also participates to the transfer of heat and salt towards the South Atlantic Ocean whose intensity is mainly related to the migration of the subtropical convergence and associated westerlies winds. This mechanism, strongly controlled by high southern latitudes dynamics, affects the global overturning circulation and plays an important role for glacial-interglacial transitions and changes in modes of climate variability during the Quaternary (Mid-Pleistocene Transition and Mid-Brunhes event). Induced Northern hemisphere climate changes, in particular ice volume, could in turn influence monsoon dynamics. On the other hand, the effect of monsoons on the Agulhas current seems to be of minor importance. However, interactions between the Indo-Asian monsoon, ENSO and the possible IOD (Indian Ocean climatic Dipole) could affect the dynamic of the current

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Sabine, Marjolaine. "Contribution relative des forçages climatiques et des processus sédimentaires dans la répartition spatio-temporelle des sédiments des mers nordiques (mers de Norvège, du Groenland et de Barents)". Thesis, Bordeaux, 2021. http://www.theses.fr/2021BORD0047.

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Ce travail présente une analyse des environnements sédimentaires marins profonds des mers nordiques à l’interface de l’Atlantique nord et de l’Arctique (mers du Groenland, de Norvège, de Barents et d’Islande) au cours du dernier million d’années. Il se base sur une base de données acoustiques (bathymétrie, imagerie multifaisceau) et sédimentologique (carottes calypso) issues de deux campagnes réalisées par le Shom. Les enregistrements sédimentaires ont montré une très grande variabilité des processus de sédimentation en jeu dans ces mers en fonction des périodes climatiques, avec notamment une sédimentation glaciomarine, gravitaire, contouritique, et hémipélagique. Ils ont également permis de se concentrer sur la chronologie des périodes de développement ou de retrait des calottes continentales périphériques (calotte du Groenland, calotte Fennoscandie et calotte de Barents et Svalbard), et du couvert de glace de mer. Une étude stratigraphique détaillée a été réalisée sur la base de différents outils (datations radiocarbones, géochimie isotopique, géochimie élémentaire, biostratigraphie sur microfossiles et nannofossiles calcaires, et analyses sédimentologiques). La reconstitution de l’historique d’évolution des apports sédimentaires et des processus responsables de ces apports depuis le Quaternaire moyen (début de la Mid-Pleistocene Transition, MPT) jusqu’à l’Holocène terminal, a permis de mieux caractériser l’impact des variations d’extension des calottes continentales sur la sédimentation des mers nordiques, mais aussi d’identifier les périodes de forte influence du couvert de glace Arctique (y compris calotte potentielle en maxima glaciaire) sur les mers nordiques, et les variations de l'influence des courants de surface et de fond dans la zone nord et la zone sud de ces bassins boréaux. Notamment, les variations d’influences des eaux de surface chaudes et salées de l’Atlantique nord ont pu être identifiées pour certaines périodes de temps
This study focuses on the study of the Middle Pleistocene to Late Quaternary sedimentation patterns and palaeoenvironmental conditions of the Nordic seas (Barents, Iceland, Norwegian and Greenland seas), which mark the transition between the North Atlantic and the Arctic oceans. It is based upon a compilation of acoustic data (bathymetry, multibeam imagery) and sedimentological data (calypso piston cores) retrieved during two cruises leaded by the Shom institute. Sedimentary records showed a large variability of the sedimentary processes at play in those seas, depending of the climatic stages and, thus, of extension or decay conditions of the surrounding ice-sheets. Glacimarine, contouritic, hemipelagic and gravity sedimentary facies are recorded in those sedimentary archives. High resolution stratigraphy was obtained using a combination of radiocarbon datings, XRF geochemistry, oxygen isotopic data and biostratigraphy. This allowed to investigate the sedimentary inputs and processes occurring in those seas from the Middle Quaternary (the beginning of the Mid-Pleistocene Transition) to the Late Holocene. It also allowed a better characterization of the variation in the boreal ice-sheet extension, and to identify periods of Atlantic Waters influence over the core sites

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Jonsson, Carl H. W. "Late-early to middle pleistocene vegetation and climate history of the Highland Valley, British Columbia, Canada". Thesis, 2017. https://dspace.library.uvic.ca//handle/1828/8922.

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The climate and vegetation history of the Middle Pleistocene transition in the interior of British Columbia (BC) is poorly understood due largely to the lack of records. Sediments from the overburden of the Teck Highland Valley Copper mine (HVC) of British Columbia straddle the Brunhes-Matuyama paleomagnetic transition, providing a opportunity to study this critical Pleistocene interval. The stratigraphy was described and sampled for paleomagnetic and pollen/spore analysis at reconnaissance scale. The HVC sediments consist mainly of (from bottom to top) a lower glacial drift, >50 m of lakebed sediments, ~50 m of gravel fan deposits, and a >60 m thick drift of mostly glacial till. These units were deposited by a valley glacier, lake, fluvial/debris flow events, and an ice sheet, respectively. Pollen and spore analyses, reveal at least 11 climate-vegetation intervals (9 zones, 2 more possible ones). These are broadly classified as either warm Pinus-Picea parkland and forest, cold Selaginella-rich steppe or arid Artemisia-Poaceae steppe. These intervals suggest a long paleo-environmental record at HVC and indicate fluctuations between glacial and interglacial climates which can tentatively be placed with Marine Isotope Stages 23 through 16 and younger. The HVC record is a unique sequence with the potential to reveal a much more detailed history of this critical time in Earth’s past. Implications of these findings are discussed.
Graduate
2018-12-06

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Capítulos de libros sobre el tema "Mid-Pleistocene transition"

Bonnefille, Raymonde, Rita Teresa Melis y Margherita Mussi. "Variability in the Mountain Environment at Melka Kunture Archaeological Site, Ethiopia, During the Early Pleistocene (~1.7 Ma) and the Mid-Pleistocene Transition (0.9–0.6 Ma)". En Vertebrate Paleobiology and Paleoanthropology, 93–114. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-75985-2_5.

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Sterelny, Kim. "The Pleistocene Social Contract". En The Pleistocene Social Contract, 54–92. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780197531389.003.0002.

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This chapter has three aims (i) it introduces the reader to the evolutionary puzzle of cooperation: why it is relatively rare despite its potential profits; (ii) it offers an account of the transition from the dominance-structured social world of the great apes and earliest hominins to a much more egalitarian and cooperative social order of the small mobile forager band of early to mid-Pleistocene hominins. Their cooperation mostly took the form of immediate return mutualism, and the chapter explains why this form of cooperation is more easily stabilized that reciprocation-dependent cooperation. (iii) It then offers an account of the transition from immediate return mutualism to cooperation through reciprocation: more efficient, potentially more profitable. But less inherently stable. The chapter connects the expansion of cultural learning to the stability of cooperation based on reciprocation.

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Willeit, Matteo. "Mid-Pleistocene Transition in Glacial Cycles Explained by Declining CO2 and Regolith Removal". En World Scientific Encyclopedia of Climate Change, 263–68. World Scientific, 2021. http://dx.doi.org/10.1142/9789811213953_0029.

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Schattner, Uri. "Early-to-mid Pleistocene Tectonic Transition Across the Eastern Mediterranean Influences the Course of Human History". En New Frontiers in Tectonic Research - At the Midst of Plate Convergence. InTech, 2011. http://dx.doi.org/10.5772/20123.

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Zheng, F., Q. Li, X. Tu, M. Chen, B. Li y Z. Jian. "Abundance Variations of Planktonic Foraminifers during Mid-Pleistocene Climate Transition at ODP Site 1144, Northern South China Sea". En Proceedings of the Ocean Drilling Program. Ocean Drilling Program, 2006. http://dx.doi.org/10.2973/odp.proc.sr.184.222.2006.

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Davias, Michael E. y Thomas H. S. Harris. "Postulating an unconventional location for the missing mid-Pleistocene transition impact: Repaving North America with a cavitated regolith blanket while dispatching Australasian tektites and giving Michigan a thumb". En In the Footsteps of Warren B. Hamilton: New Ideas in Earth Science. Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2553(24).

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ABSTRACT This thesis embraces and expands upon a century of research into disparate geological enigmas, offering a unifying catastrophic explanation for events occurring during the enigmatic mid-Pleistocene transition. Billions of tons of “Australasian tektites” were dispatched as distal ejecta from a target mass of continental sediments during a cosmic impact occurring ca. 788 ka. The accepted signatures of a hypervelocity impact encompass an excavated astrobleme and attendant proximal, medial, and distal ejecta distributions. Enigmatically, the distal tektites remain the only accepted evidence of this impact’s reality. A protracted 50 yr search fixated on impact sites in Southeast Asia—the location of the tektites—has failed to identify the requisite additional impact signatures. We postulate the missing astrobleme and proximal/medial ejecta signatures are instead located antipodal to Southeast Asia. A review of the gradualistic theories for the genesis and age of the “Carolina bay” landforms of North America finds those models incapable of addressing all the facts we observe. Research into 57,000 of those oriented basins informs our speculation that they represent cavitation-derived ovoid basins within energetically delivered geophysical mass surge flows emanating from a cosmic impact. Those flows are seen as repaving regions of North America under blankets of hydrated impact regolith. Our precisely measured Carolina bay orientations indicate an impact site within the Laurentide ice sheet. There, we invoke a grazing regime impact into hydrated early Mesozoic to late Paleozoic continental sediments, similar in composition to the expected Australasian tektites’ parent target. We observe that continental ice shielded the target at ca. 788 ka, a scenario understood to produce anomalous astroblemes. The ensuing excavation allowed the Saginaw glacial lobe’s distinctive and unique passage through the Marshall Sandstone cuesta, which encircles and elsewhere protects the central region of the intracratonic Michigan Basin. Subsequent erosion by multiple ice-age transgressions has obfuscated impact evidence, forming Michigan’s “Thumb” as an enduring event signature. Comprehensive suborbital modeling supports the distribution of distal ejecta to the Australasian tektite strewn field from Michigan’s Lower Peninsula. The mid-Pleistocene transition impact hypothesis unifies the Carolina bays with those tektites as products of an impact into the Saginaw Bay area of Lake Huron, USA. The hypothesis will be falsified if cosmogenic nuclide burial dating of Carolina bay subjacent stratigraphic contacts disallows a coeval regolith emplacement ca. 788 ka across North America. We offer observations, interdisciplinary insights, and informed speculations fitting for an embryonic concept involving a planetary-scale extraterrestrial impact.

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Stine, J., D. E. Sweet, J. W. Geissman, H. Baird y J. F. Ferguson. "Climate and provenance variation across the mid-Pleistocene transition revealed through sedimentology, geochemistry, and rock magnetism of the Blackwater Draw Formation, Southern High Plains, Texas, USA". En Untangling the Quaternary Period—A Legacy of Stephen C. Porter. Geological Society of America, 2020. http://dx.doi.org/10.1130/2020.2548(03).

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Foster, David R. y B. L. Turner II. "The Long View: Human–Environment Relationships in the Region, 1000 BC–AD 1900". En Integrated Land-Change Science and Tropical Deforestation in the Southern Yucatan. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780199245307.003.0010.

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The Yucatán Peninsula is a thick, low-lying, limestone shelf that rose fully above the Caribbean Sea and Gulf of Mexico during the Pleistocene (Folan 1983; Wilson 1980). Given its calcite and dolomite base, the entire peninsula northward from the Libertad Arch, which extends east–west across the central Petén, is a karstic landscape of coastal plains and interior uplands or hills dominated by solution features and subsurface drainage (Finch 1965; Jennings 1985; Weidie and Ward 1976; Wilhemy 1981). Permanent rivers and streams appear only in the southern, high rainfall, portion of the peninsula, largely along the lower-lying coastal plains and adjacent edges of the interior uplands. For the most part, the southern Yucatán peninsular region constitutes an undulating upland (about 80% of the landscape) composed of ridges and, to the south, cone karst (Figs. 2.1 and 2.2: upland-bajo distribution). Interspersed among the uplands are large, surface solution sinks or poljes (Weidie and Ward 1976), locally known as bajos (sometimes, akalches). These features infill with sediments, predominately montmorillonite clays, which impede subsurface drainage and retain surface water built up during the rainy season, creating seasonal wetlands. Otherwise, water percolates through the upland karst to subterranean aquifers, which generally lie deep below the surface. In the uplands proper, these aquifers may be more than 200m below the surface (Turner, 1983). The region occupies a transitional position between tropical monsoon (Am, Köppen classification) and tropical wet-dry (Aw) climates to the south and north respectively. The critical distinction between the two is the length and severity of the dry season, which increases northward. Overall, the climate is characterized by hot, humid summers and warm, dry winters, in which nortes (cold northern airstreams) penetrate the region for brief periods. Average annual precipitation ranges from about 900mm to in excess of 1,400mm, increasing to the south, the large majority of which falls during the wet season (mid-May through October) (Garcia 1970). Water deficits exist throughout the region during the mid-to-late dry season, stressing vegetation, wildlife, agriculture, livestock, and human settlement.

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Actas de conferencias sobre el tema "Mid-Pleistocene transition"

Tripathi, Shubham. "Eastern Arabian Sea Climate Change during Mid-Pleistocene Transition". En Goldschmidt2021. France: European Association of Geochemistry, 2021. http://dx.doi.org/10.7185/gold2021.3284.

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Jonas, A. S., M. A. C. Kars, T. Bauersachs, W. Rübsam y L. Schwark. "Decoupling of Nw Pacific from Global Climate Evolution Linked to the Mid-Pleistocene Transition and Mid-Brunhes Event". En 29th International Meeting on Organic Geochemistry. European Association of Geoscientists & Engineers, 2019. http://dx.doi.org/10.3997/2214-4609.201903064.

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Evans, Erica S. J. y Alan D. Rooney. "TESTING THE REGOLITH HYPOTHESIS: INVESTIGATING SUBSTRATE CHANGE THROUGH THE MID-PLEISTOCENE TRANSITION USING OSMIUM ISOTOPES". En GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-336850.

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Sweet, Dustin E., Jonathan Stine y J. W. Geissman. "THE EFFECT OF THE MID-PLEISTOCENE TRANSITION ON THE CHARACTER OF SEDIMENTATION ON THE SOUTHERN HIGH PLAINS". En GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-298799.

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Lindberg, Kurt, William Daniels, Isla S. Castaneda, Jeffrey M. Salacup y Julie Brigham-Grette. "TEMPERATURE VARIABILITY FROM ARCTIC LAKE EL’GYGYTGYN (FAR EAST RUSSIA) DURING THE MID-PLEISTOCENE TRANSITION BASED ON BRGDGTS". En Joint 69th Annual Southeastern / 55th Annual Northeastern GSA Section Meeting - 2020. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020se-344663.

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Petronis, Michael, R. Scott Anderson, Peter J. Fawcett, Spencer E. Staley y Sindy Lauricella. "PALEOMAGNETIC DATA FROM STONEMAN LAKE, ARIZONA PLACING CONSTRAINTS ON THE EVOLUTION OF TERRESTRIAL CLIMATE AND VEGETATION THROUGH THE MID PLEISTOCENE TRANSITION". En GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-337129.

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Starr, Aidan, Ian Hall, Stephen Barker, Sidney Hemming, Thomas Rackow, Xu Zhang, H. J. L. van der Lubbe et al. "The interglacial-glacial sequence of events at the Agulhas Plateau: Antarctic icebergs lead ocean circulation into ice ages and across the Mid-Pleistocene Transition". En Goldschmidt2021. France: European Association of Geochemistry, 2021. http://dx.doi.org/10.7185/gold2021.7345.

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Davias, Michael y Thomas H. S. Harris. "AN INCOMPREHENSIBLE COSMIC IMPACT AT THE MID PLEISTOCENE TRANSITION; SEARCHING FOR THE MISSING CRATER USING AUSTRALASIAN TEKTITE SUBORBITAL ANALYSIS AND CAROLINA BAYS' MAJOR AXES TRIANGULATION". En GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-332326.

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Lauricella, Sindy, Michael Petronis, Michael Petronis, Peter J. Fawcett, Peter J. Fawcett, R. Scott Anderson, R. Scott Anderson, Spencer E. Staley y Spencer E. Staley. "PRELIMINARY PALEOMAGNETIC DATA BEARING ON THE EVOLUTION OF TERRESTRIAL CLIMATE AND VEGETATION THROUGH THE MID-PLEISTOCENE TRANSITION: A 1.5 MA RECORD FROM STONEMAN LAKE, ARIZONA". En Joint 70th Annual Rocky Mountain GSA Section / 114th Annual Cordilleran GSA Section Meeting - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018rm-313950.

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Houghton, Jennifer, Daniele Scarponi y David Fike. "Impact of depositional facies on marine sedimentary pyrite textures and sulfur isotopes: a case study of the Early-Mid Pleistocene transition from the Valle di Manche section (Crotone Basin, Southern Italy)". En Goldschmidt2021. France: European Association of Geochemistry, 2021. http://dx.doi.org/10.7185/gold2021.4152.

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