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Registros recuperados: 14
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Analyzing Large Paleoclimate Datasets: Implications for Past and Future Climate Change. ArchiMer
Shakun, Jeremy D.
This dissertation presents the results of statistical analyses of large climate datasets from two time intervals – the 20th century instrumental record and the proxy record of the last deglaciation – in order to understand the forcings and mechanisms of past climate variability. A longstanding question in climate dynamics concerns the origin of Pacific decadal variability (PDV). This issue is addressed by calculating the Southern Hemisphere equivalent of the Pacific Decadal Oscillation (PDO) index from Pacific sea surface temperature (SST) anomalies over the 20th century, which is found to be similar to its Northern Hemisphere counterpart. The Northern and Southern PDO indices both exhibit pronounced seasonality in autocorrelation with interannual...
Tipo: Text Palavras-chave: El Nino-Southern Oscillation; Pacific Decadal Oscillation; Paleoclimate; Deglaciation; Ocean circulation; Milankovitch; Greenhouse gases.
Ano: 2010 URL: https://archimer.ifremer.fr/doc/00495/60654/64151.pdf
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Constraints on Black Sea outflow to the Sea of Marmara during the last glacial-interglacial transition ArchiMer
Major, Candace; Ryan, William; Lericolais, Gilles; Hajdas, Irka.
New cores from the upper continental slope off Romania in the western Black Sea provide a continuous, high-resolution record of sedimentation rates, clay mineralogy, calcium carbonate content, and stable isotopes of oxygen and carbon over the last 20000 yr in the western Black Sea. These records all indicate major changes occurring at 15 000, 12 800, 8400, and 7 100 yr before present. These results are interpreted to reflect an evolving balance between water supplied by melting glacial ice and other river runoff and water removed by evaporation and outflow. The marked retreat of the Fennoscandian and Alpine ice between 15 000 and 14 000 yr is recorded by an increase in clays indicative of northern provenance in Black Sea sediments. A short return toward...
Tipo: Text Palavras-chave: Clay mineralogy; Stable isotopes; Sapropel; Younger Dryas; Deglaciation.
Ano: 2002 URL: http://archimer.ifremer.fr/doc/2002/publication-473.pdf
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Deglacial delta δ18 and hydrologic variability in the tropical Pacific and Indian Oceans ArchiMer
Gibbons, Fern T.; Oppo, Delia W.; Mohtadi, Mahyar; Rosenthal, Yair; Cheng, Jun; Liu, Zhengyu; Linsley, Braddock K..
Evidence from geologic archives suggests that there were large changes in the tropical hydrologic cycle associated with the two prominent northern hemisphere deglacial cooling events, Heinrich Stadial 1 (HS1; similar to 19 to 15 kyr BP; kyr BP = 1000 yr before present) and the Younger Dryas (similar to 12.9 to 11.7 kyr BP). These hydrologic shifts have been alternatively attributed to high and low latitude origin. Here, we present a new record of hydrologic variability based on planktic foraminifera-derived delta O-18 of seawater (delta O-18(sw)) estimates from a sediment core from the tropical Eastern Indian Ocean, and using 12 additional delta O-18(sw) records, construct a single record of the dominant mode of tropical Eastern Equatorial Pacific and...
Tipo: Text Palavras-chave: Indo-Pacific; Eastern Equatorial Pacific; Delta O-18 of seawater; Deglaciation; Heat transport.
Ano: 2014 URL: https://archimer.ifremer.fr/doc/00496/60737/65207.pdf
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Devising quality assurance procedures for assessment of legacy geochronological data relating to deglaciation of the last British-Irish Ice Sheet ArchiMer
Small, David; Clark, Chris D.; Chiverrell, Richard C.; Smedley, Rachel K.; Bateman, Mark D.; Duller, Geoff A. T.; Ely, Jeremy C.; Fabel, Derek; Medialdea, Alicia; Moreton, Steven G..
This contribution documents the process of assessing the quality of data within a compilation of legacy geochronological data relating to the last British-Irish Ice Sheet, a task undertaken as part of a larger community-based project (BRITICE-CHRONO) that aims to improve understanding of the ice sheet's deglacial evolution. As accurate reconstructions depend on the quality of the available data, some form of assessment is needed of the reliability and suitability of each given age(s) in our dataset. We outline the background considerations that informed the quality assurance procedures devised given our specific research question. We describe criteria that have been used to make an objective assessment of the likelihood that an age is influenced by the...
Tipo: Text Palavras-chave: British-Irish Ice Sheet; Deglaciation; Geochronology; Data compilations; Quality assurance; Bayesian.
Ano: 2017 URL: https://archimer.ifremer.fr/doc/00504/61598/65865.pdf
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External controls on turbidite sedimentation on the glacially-influenced Armorican margin (Bay of Biscay, western European margin) ArchiMer
Toucanne, Samuel; Zaragosi, Sebastien; Bourillet, Jean-francois; Dennielou, Bernard; Jorry, Stephan; Jouet, Gwenael; Cremer, Michel.
Sequence stratigraphic models predict increased sediment delivery to deep-water areas during sea-level lowstand. The Armorican margin (Bay of Biscay, western European margin) is an interesting area to test this hypothesis because the margin has a wide continental shelf, still partly flooded during sea-level lowstand, and the Armorican turbidite system has experienced fluctuating sediment fluxes since the last glacial period. The stratigraphic response of the Armorican turbidite system to sea-level oscillations and climate changes was assessed for the last 35,000 years through the study of the Guilcher, Crozon and Audierne levees. Millenial-timescale resolution chronostratigraphy allowed us to reconstruct the sediment accumulation and turbidite frequency,...
Tipo: Text Palavras-chave: Armorican margin; Bay of Biscay; Turbidite systems; Turbidity currents; Levee growth; External forcing; Deglaciation; Source-to-sink.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00070/18147/15708.pdf
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Glacial hydrologic conditions in the Black Sea reconstructed using geochemical pore water profiles ArchiMer
Soulet, Guillaume; Delaygue, G.; Vallet-coulomb, C.; Boettcher, M. E.; Sonzogni, C.; Lericolais, Gilles; Bard, E..
Chloride and delta O-18 compositions of interstitial water extracted from a long sediment core retrieved from the NW coast of the Black Sea allowed us to constrain the main hydrologic changes of the Back Sea during the Late Pleistocene and Holocene. Prior to its reconnection with the Mediterranean Sea (through the Marmara Sea) at approximately 9000 calendar yr before present (9 ka cal BP), the Black Sea has evolved as a fresh to brackish water lake. At the time of reconnection, hydrologic changes were drastic. Bottom water salinities changed from a few psu (practical salinity unit) to similar to 22 psu. Since solutes in the interstitial water column within sediments are advected and diffused the measured concentrations do not reflect those of past bottom...
Tipo: Text Palavras-chave: Black Sea; Interstitial water; Salinity; Water isotopes; Advection/diffusion modelling; Deglaciation.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00011/12239/9798.pdf
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Large sensitivity to freshwater forcing location in 8.2ka simulations ArchiMer
Morrill, Carrie; Ward, Ellen M.; Wagner, Amy J.; Otto-bliesner, Bette L.; Rosenbloom, Nan.
The 8.2ka event is a key test case for simulating the coupled climate response to changes in the Atlantic Meridional Overturning Circulation (AMOC). Recent advances in quantifying freshwater fluxes at 8.2ka from the proxy record have improved the realism of the forcing magnitude in model simulations, yet this forcing is still generally applied in an unrealistic geographic manner, across most of the Labrador Sea rather than just along the Labrador coast. Previous simulations with eddy- resolving ocean models have come to conflicting conclusions regarding the ability of such a coastally confined flow to impact the AMOC. These simulations have also not incorporated full atmosphere models nor have they used the new meltwater forcing values for 8.2ka. We use...
Tipo: Text Palavras-chave: Atlantic Meridional Overturning Circulation; Abrupt climate change; Deglaciation; 8; 2 ka event; Freshwater forcing; Coupled climate model simulation.
Ano: 2014 URL: https://archimer.ifremer.fr/doc/00496/60735/65213.pdf
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Methane seepage at Vestnesa Ridge (NW Svalbard) since the Last Glacial Maximum ArchiMer
Schneider, A.; Panieri, G.; Lepland, A.; Consolaro, C.; Cremiere, A.; Forwick, M.; Johnson, J. E.; Plaza-faverola, A.; Sauer, S.; Knies, J..
Multiple proxies in the geological record offshore NW Svalbard track shallow subseafloor diagenesis and seafloor methane seepage during the Last Glacial Maximum (LGM) extent and the disintegration of the Svalbard Barents Sea Ice Sheet (SBIS). Vestnesa Ridge, located at 79°N and in 1200 m water depth, is one of the northernmost known active methane seep sites and is characterised by a subseafloor fluid flow system, numerous seafloor pockmarks and gas flares in the water column. In this study, we develop a Late Pleistocene and Holocene stratigraphic framework, use stable oxygen and carbon isotope signatures (δ18O, δ13C) of benthic and planktic foraminifera, the mineralogical and carbon isotope composition of methane-derived authigenic carbonate (MDAC) and...
Tipo: Text Palavras-chave: Micropaleontology; Foraminifers; Stable isotopes; Methane seepage; Authigenic carbonate; Holocene; Pleistocene; Paleogeography; Deglaciation; Arctic Ocean.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00445/55652/60554.pdf
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Millennial-scale fluctuations of the European Ice Sheet at the end of the last glacial, and their potential impact on global climate ArchiMer
Toucanne, Samuel; Soulet, Guillaume; Freslon, Nicolas; Jacinto, Ricardo Silva; Dennielou, Bernard; Zaragosi, Sebastien; Eynaud, Frederique; Bourillet, Jean-francois; Bayon, Germain.
Reconstructing Northern Hemisphere ice-sheet oscillations and meltwater routing to the ocean is important to better understand the mechanisms behind abrupt climate changes. To date, research efforts have mainly focused on the North American (Laurentide) ice-sheets (LIS), leaving the potential role of the European Ice Sheet (EIS), and of the Scandinavian ice-sheet (SIS) in particular, largely unexplored. Using neodymium isotopes in detrital sediments deposited off the Channel River, we provide a continuous and well-dated record for the evolution of the EIS southern margin through the end of the last glacial period and during the deglaciation. Our results reveal that the evolution of EIS margins was accompanied with substantial ice recession (especially of...
Tipo: Text Palavras-chave: European ice-sheet; Channel River; Meltwater; Deglaciation; Neodymium; Termination.
Ano: 2015 URL: https://archimer.ifremer.fr/doc/00272/38346/36675.pdf
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New constraints on deglacial marine radiocarbon anomalies from a depth transect near Baja California ArchiMer
Lindsay, Colin M.; Lehman, Scott J.; Marchitto, Thomas M.; Carriquiry, Jose D.; Ortiz, Joseph D..
Previous studies have shown that radiocarbon activities (C-14) in the low-latitude, middepth Pacific and Indian Oceans were anomalously low during Heinrich Stadial 1 (HS1, similar to 17.8-14.6ka) and the Younger Dryas (YD, similar to 12.8-11.5ka), coincident with intervals of rising atmospheric CO2 concentration and declining atmospheric C-14. However, a full explanation of these events remains elusive due to sparse and sometimes conflicting data. Here we present new C-14 measurements on benthic and planktic foraminifera that, in combination with previously published measurements, enable us to reconstruct the C-14 depth gradient near Baja California. Vertical profiles were similar to present during the Last Glacial Maximum and BOlling/Allerod (14.6-12.8ka)...
Tipo: Text Palavras-chave: Radiocarbon; Deglaciation; Heinrich Stadial 1; Baja California; Benthic foraminifera.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00496/60797/64925.pdf
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The co-evolution of Black Sea level and composition through the last deglaciation and its paleoclimatic significance ArchiMer
Major, Candace O.; Goldstein, Steven L.; Ryan, William B.f.; Lericolais, Gilles; Piotrowski, Alexander M.; Hajdas, Irka.
The Black Sea was an inland lake during the last ice age and its sediments are an excellent potential source of information on Eurasian climate change, showing linkages between regionally and globally recognized millennial-scale climate events of the last deglaciation. Here, we detail changes from the last glacial maximum (LGM) through the transition to an anoxic marginal sea using isotopic (strontium and oxygen) and trace element (Sr/Ca) ratios in carbonate shells, which record changing input sources and hydrologic conditions in the basin and surrounding region. Sr isotope records show two prominent peaks between similar to 18 and 16 ka BP cal, reflecting anomalous sedimentation associated with meltwater from disintegrating Eurasian ice sheets that...
Tipo: Text Palavras-chave: Sea level changes; Black Sea; Deglaciation; Glaciation; Palaeoclimate; Palaeoceanography.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-2006.pdf
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The deglaciation of the northwest sector of the last British-Irish ice sheet : integrating onshore and offshore data relating to chronology and behaviour ArchiMer
Small, David.
It is now accepted that the last British-Irish Ice Sheet (BIIS) was highly dynamic and drained by numerous fast flowing ice streams. This dynamic nature combined with its maritime location made the BIIS sensitive to the rapid climate change that characterised the Last Glacial Interglacial Transition. Gaining an understanding of the behaviour of the BIIS at this time is important to explore the nature of forcing between ice sheets and climate. This thesis presents new chronological data relating to the deglaciation of the northwest sector of the BIIS (NW-BIIS) from onshore dating of moraines using cosmogenic exposure dating. This improved chronological framework is supported by offshore data in the form of a newly constructed Ice Rafted Detritus (IRD)...
Tipo: Text Palavras-chave: British-Irish Ice Sheet; Deglaciation; Cosmogenic; Ice rafted detritus; Provenance; Environmental change.
Ano: 2013 URL: https://archimer.ifremer.fr/doc/00499/61039/64446.pdf
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The first estimation of Fleuve Manche palaeoriver discharge during the last deglaciation: Evidence for Fennoscandian ice sheet meltwater flow in the English Channel ca 20-18 ka ago ArchiMer
Toucanne, Samuel; Zaragosi, Sebastien; Bourillet, Jean-francois; Marieu, Vincent; Cremer, Michel; Kageyama, Masa; Van Vliet-lanoe, Brigitte; Eynaud, Frederique; Turon, Jean-louis; Gibbard, Philip L..
The Fleuve Manche (English Channel) palaeoriver represents the largest river system that drained the European continent during Pleistocene lowstands, particularly during the Elsterian (Marine Isotope Stage 12) and Saalian Drenthe (MIS 6) glaciations when extensive ice advances into the North Sea area forced the central European rivers to flow southwards to the Bay of Biscay (NE Atlantic). Numerous long piston cores and high-resolution acoustic data from the northern Bay of Biscay have been correlated using a well-constrained chronostratigraphical framework, and for the first time allow the estimation of the discharge of the Fleuve Manche palaeoriver at the end of the last glacial period (i.e. Weichselian). Our results, discussed in the light of...
Tipo: Text Palavras-chave: Fleuve Manche palaeoriver; English Channel; Sediment and meltwater discharge; European ice sheet; Deglaciation; Termination 1; North Sea area; European drainage network.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00002/11310/7858.pdf
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The last glacial maximum ans deglaciation in central Patagonia, 44°S-49°S ArchiMer
Mendelova, M.; Hein, A. S.; Mcculloch, R.; Davies, B..
This paper reviews published geochronological data on glacier fluctuations and environmental changes in central Patagonia (44 degrees S-49 degrees S) from the Last Glacial Maximum (LGM) through to the Holocene. Well-dated glacial chronologies from the southern mid-latitudes can inform on the synchronicity of glacial advances worldwide and provide insight on the drivers of southern hemisphere glaciations. In central Patagonia, two large outlet lobes of the former Patagonian Ice Sheet advanced in broad synchrony with the global LGM. In contrast to other parts of Patagonia, there is no convincing evidence for a more extensive local LGM advance during Marine Isotope Stage 3. Deglaciation initiated at ca. 19 ka, earlier than in other parts of Patagonia and...
Tipo: Text Palavras-chave: Last Glacial Maximum; Deglaciation; Holocene; Patagonia; Glacial chronology.
Ano: 2017 URL: https://archimer.ifremer.fr/doc/00497/60830/64500.pdf
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