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| Registros recuperados: 28 | |
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| 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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| Calvo, Eva; Pelejero, Carles; De Deckker, Patrick; Logan, Graham A.. |
| Comparison of ice cores from Greenland and Antarctica shows an asynchronous two-step warming at these high latitudes during the Last Termination. However, the question whether this asynchrony extends to lower latitudes is unclear mainly due to the scarcity of paleorecords from the Southern Hemisphere. New data from a marine core collected off South Australia (similar to 36 degrees S) allows a detailed reconstruction of sea-surface temperatures over the Last Termination. This confirms the existence of an Antarctic-type deglacial pattern and shows no indication of cooling associated with the Northern Hemisphere YD event. The SST record also provides a new comparison with the more extensive paleoclimatic data available from continental Australia. This shows a... |
| Tipo: Text |
Palavras-chave: Alkenones; Deglaciation; Southern Hemisphere. |
| Ano: 2007 |
URL: https://archimer.ifremer.fr/doc/00235/34647/33013.pdf |
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| Skinner, L. C.; Freeman, E.; Hodell, D.; Waelbroeck, C.; Vazquez Riveiros, Natalia; Scrivner, A.e. |
| Changes in ocean ventilation, controlled by both overturning rates and air‐sea gas exchange, are thought to have played a central role in atmospheric CO2 rise across the last deglaciation. Here we constrain the nature of Atlantic Ocean ventilation changes over the last deglaciation using radiocarbon and stable carbon isotopes from two depth transects in the Atlantic basin. Our findings broadly cohere with the established pattern of deglacial Atlantic overturning change, and underline the existence of active northern sourced deep‐water export at the Last Glacial Maximum (LGM). We find that the western Atlantic was less affected by incursions of southern‐sourced deep water, as compared to the eastern Atlantic, despite both sides of the basin being strongly... |
| Tipo: Text |
Palavras-chave: Air‐ Sea exchange; AMOC; Carbon cycle; Deglaciation; Radiocarbon; Ventilation. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00665/77717/79810.pdf |
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| 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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| Small, David; Benetti, Sara; Dove, Dayton; Ballantyne, Colin K.; Fabel, Derek; Clark, Chris D.; Gheorghiu, Delia M.; Newall, Jennifer; Xu, Sheng. |
| Understanding how marine-based ice streams operated during episodes of deglaciation requires geochronological data that constrain both timing of deglaciation and changes in their flow behaviour, such as that from unconstrained ice streaming to topographically restricted flow. We present seventeen new Be-10 exposure ages from glacial boulders and bedrock at sites in western Scotland within the area drained by the Hebrides Ice Stream, a marine-based ice stream that drained a large proportion of the former British-Irish Ice Sheet. Exposure ages from Tiree constrain deglaciation of a topographic high within the central zone of the ice stream, from which convergent flowsets were produced during ice streaming. These ages thus constrain thinning of the Hebrides... |
| Tipo: Text |
Palavras-chave: Exposure dating; Marine ice stream; British-Irish ice sheet; Deglaciation. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00420/53148/55337.pdf |
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| Lippold, Jorg; Gutjahr, Marcus; Blaser, Patrick; Christner, Emanuel; Ferreria, Maria Luiza De Carvalho; Mulitza, Stefan; Christl, Marcus; Wombacher, Frank; Böhm, Evelyn; Antz, Benny; Cartapanis, Olivier; Vogel, Hendrik; Jaccard, Samuel L.. |
| Reconstructing past modes of ocean circulation is an essential task in paleoclimatology and paleoceanography. To this end, we combine two sedimentary proxies, Nd isotopes (epsilon(Nd)) and the Pa-231/Th-230 ratio, both of which are not directly involved in the global carbon cycle, but allow the reconstruction of water mass provenance and provide information about the past strength of overturning circulation, respectively. In this study, combined Pa-231/Th-230 and epsilon(Nd) down-core profiles from six Atlantic Ocean sediment cores are presented. The data set is complemented by the two available combined data sets from the literature. From this we derive a comprehensive picture of spatial and temporal patterns and the dynamic changes of the Atlantic... |
| Tipo: Text |
Palavras-chave: Pa-231/Th-230; Epsilon(Nd); Atlantic Meridional Overturning Circulation; Deep sea sediments; Last Glacial Maximum; Deglaciation. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53236/54762.pdf |
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| 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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| Meckler, A. Nele; Haug, Gerald H.; Sigman, Daniel M.; Plessen, Birgit; Peterson, Larry C.; Thierstein, Hans R.. |
| For the last deglaciation and Termination V ( the initiation of MIS 11 at around 430 ka) we report high-resolution sedimentary nitrogen isotope (delta(15)N)records from Cariaco Basin in the Caribbean Sea. During both terminations the previously reported interglacial decrease in delta(15)N clearly lags local changes such as water column anoxia as well as global increases in denitrification by several thousand years. On top of the glacial-interglacial change, several delta(15)N peaks were observed during the last deglaciation. The deglacial signal in Cariaco Basin can be best explained as a combination of (1) local variations in suboxia and water column denitrification as the reason for the millennial-scale peaks, (2) a deglacial maximum in mean ocean... |
| Tipo: Text |
Palavras-chave: Cariaco Basin; N fixation; Deglaciation. |
| Ano: 2007 |
URL: https://archimer.ifremer.fr/doc/00233/34457/32869.pdf |
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| 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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| 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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| Small, David; Austin, William; Rinterknecht, Vincent. |
| A sediment core from the north-east North Atlantic contains high-resolution co-registered foraminiferal O-18 and ice-rafted detritus (IRD) records for the last deglaciation. These reveal a distinct ice-rafting event that occurred at the time of Greenland Interstade 1d (GI-1d), a feature also seen in other high-resolution cores from the North Atlantic. The occurrence of a geographically widespread peak in IRD at ice distal sites at a time when increased freshwater flux to the surface ocean is inferred to have caused rapid cooling suggests a mechanistic link between the processes, analogous to the Younger Dryas (GS-1) cooling episode. The general absence of IRD at southern locations at other times during GI-1 when the flux of icebergs from surviving ice... |
| Tipo: Text |
Palavras-chave: Deglaciation; Hydrography; Ice-rafted detritus; North Atlantic; Sea surface temperature. |
| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00291/40180/39238.pdf |
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| Gherardi, Jeanne Marie; Labeyrie, L.; Nave, S.; Francois, R.; Mcmanus, J. F.; Cortijo, E.. |
| Studies from the subtropical western and eastern Atlantic Ocean, using the Pa-231/Th-230 ratio as a kinematic proxy for deep water circulation, provided compelling evidence for a strong link between climate and the rate of meridional overturning circulation (MOC) over the last deglaciation. In this study, we present a compilation of existing and new sedimentary Pa-231/Th-230 records from North Atlantic cores between 1710 and 4550 m water depth. Comparing sedimentary Pa-231/Th-230 from different depths provides new insights into the evolution of the geometry and rate of deep water formation in the North Atlantic during the last 20,000 years. The Pa-231/Th-230 ratio measured in upper Holocene sediments indicates slow water renewal above similar to 2500 m and... |
| Tipo: Text |
Palavras-chave: MOC; North Atlantic; Deglaciation; 231Pa/230Th. |
| Ano: 2009 |
URL: https://archimer.ifremer.fr/doc/00233/34468/32855.pdf |
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| Meyer, Vera D.; Max, Lars; Hefter, Jens; Tiedemann, Ralf; Mollenhauer, Gesine. |
| It has been proposed that North Pacific sea surface temperature (SST) evolution was intimately linked to North Atlantic climate oscillations during the last glacial-interglacial transition. However, during the early deglaciation and the Last Glacial Maximum, the SST development in the subarctic northwest Pacific and the Bering Sea is poorly constrained as most existing deglacial SST records are based on alkenone paleothermometry, which is limited prior to 15ka B.P. in the subarctic North Pacific realm. By applying the TEX86L temperature proxy we obtain glacial-Holocene-SST records for the marginal northwest Pacific and the Western Bering Sea. Our TEX86L-based records and existing alkenone data suggest that during the past 15.5ka, SSTs in the northwest... |
| Tipo: Text |
Palavras-chave: TEX86L; Surface circulation; Northwest Pacific; Bering Sea; Deglaciation. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53231/54786.pdf |
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| Small, David; Rinterknecht, Vincent; Austin, William E. N.; Bates, Richard; Benn, Douglas I.; Scourse, James D.; Bourles, Didier L.; Hibbert, Fiona D.. |
| Geochronological constraints on the deglaciation of former marine based ice streams provide information on the rates and modes by which marine based ice sheets have responded to external forcing factors such as climate change. This paper presents new 36Cl cosmic ray exposure dating from boulders located on two moraines (Glen Brittle and Loch Scavaig) in southern Skye, northwest Scotland. Ages from the Glen Brittle moraines constrain deglaciation of a major marine terminating ice stream, the Barra-Donegal Ice Stream that drained the former British-Irish Ice Sheet, depending on choice of production method and scaling model this occurred 19.9 ± 1.5–17.6 ± 1.3 ka ago. We compare this timing of deglaciation to existing geochronological data and changes in a... |
| Tipo: Text |
Palavras-chave: Deglaciation; Scotland; Cosmogenic exposure ages; Chlorine-36. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00349/46010/83047.pdf |
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| 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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| 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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| Registros recuperados: 28 | |
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