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Registros recuperados: 5
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Agulhas salt-leakage oscillations during abrupt climate changes of the Late Pleistocene 5
Marino, Gianluca; Zahn, Rainer; Ziegler, Martin; Purcell, Conor; Knorr, Gregor; Hall, Ian R.; Ziveri, Patrizia; Elderfield, Henry.
An ensemble of new, high-resolution records of surface ocean hydrography from the Indian-Atlantic oceanic gateway, south of Africa, demonstrates recurrent and high-amplitude salinity oscillations in the Agulhas Leakage area during the penultimate glacial-interglacial cycle. A series of millennial-scale salinification events, indicating strengthened salt leakage into the South Atlantic, appear to correlate with abrupt changes in the North Atlantic climate and Atlantic Meridional Overturning Circulation (AMOC). This interhemispheric coupling, which plausibly involved changes in the Hadley Cell and midlatitude westerlies that impacted the interocean transport at the tip of Africa, suggests that the Agulhas Leakage acted as a source of negative buoyancy for...
Tipo: Text Palavras-chave: Agulhas Leakage; Abrupt climate change; Millennial-scale variability; AMOC; Bipolar seesaw; Southern Hemisphere atmospheric circulation.
Ano: 2013 URL: https://archimer.ifremer.fr/doc/00264/37493/35791.pdf
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Benthic foraminiferal oxygen isotope offsets over the last glacial-interglacial cycle 5
Hoogakker, Babette; Elderfield, Henry; Oliver, Kevin; Crowhurst, Simon.
The oxygen isotope (delta(18)O) offset between contemporaneous benthic foraminiferal species is often assumed constant with time and geographic location. We present an inventory of benthic foraminiferal species delta(18)O offsets from the major ocean basins covering the last glacial-interglacial cycle, showing that of the twenty down-core records investigated, twelve show significant temporal changes in delta(18)O offsets that do not resemble stochastic variability. Some of the temporal changes may be related to kinetic fractionation effects causing deglacial/interglacial enrichment or glacial depletion in mainly infaunal species, but additional research is needed to confirm this. In addition to stratigraphic implications the finding of temporally varying...
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Ano: 2010 URL: https://archimer.ifremer.fr/doc/00230/34133/33061.pdf
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Evolution of South Atlantic density and chemical stratification across the last deglaciation 5
Roberts, Jenny; Gottschalk, Julia; Skinner, Luke C.; Peck, Victoria L.; Kender, Sev; Elderfield, Henry; Waelbroeck, Claire; Riveiros, Natalia Vazquez; Hodell, David A..
Explanations of the glacial-interglacial variations in atmospheric pCO(2) invoke a significant role for the deep ocean in the storage of CO2. Deep-ocean density stratification has been proposed as a mechanism to promote the storage of CO2 in the deep ocean during glacial times. A wealth of proxy data supports the presence of a "chemical divide" between intermediate and deep water in the glacial Atlantic Ocean, which indirectly points to an increase in deep-ocean density stratification. However, direct observational evidence of changes in the primary controls of ocean density stratification, i.e., temperature and salinity, remain scarce. Here, we use Mg/Ca-derived seawater temperature and salinity estimates determined from temperature-corrected delta O-18...
Tipo: Text Palavras-chave: South Atlantic; Density gradient; Ocean stratification; Last deglaciation; Atmospheric CO2.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00421/53276/54569.pdf
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Mid Pleistocene foraminiferal mass extinction coupled with phytoplankton evolution 5
Kender, Sev; Mcclymont, Erin L.; Elmore, Aurora C.; Emanuele, Dario; Leng, Melanie J.; Elderfield, Henry.
Understanding the interaction between climate and biotic evolution is crucial for deciphering the sensitivity of life. An enigmatic mass extinction occurred in the deep oceans during the Mid Pleistocene, with a loss of over 100 species (20%) of sea floor calcareous foraminifera. An evolutionarily conservative group, benthic foraminifera often comprise 450% of eukaryote biomass on the deep-ocean floor. Here we test extinction hypotheses (temperature, corrosiveness and productivity) in the Tasman Sea, using geochemistry and micropalaeontology, and find evidence from several globally distributed sites that the extinction was caused by a change in phytoplankton food source. Coccolithophore evolution may have enhanced the seasonal 'bloom' nature of primary...
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Ano: 2016 URL: https://archimer.ifremer.fr/doc/00496/60723/65259.pdf
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Obliquity pacing of the western Pacific Intertropical Convergence Zone over the past 282,000 years 5
Liu, Yi; Lo, Li; Shi, Zhengguo; Wei, Kuo-yen; Chou, Chien-ju; Chen, Yi-chi; Chuang, Chih-kai; Wu, Chung-che; Mii, Horng-sheng; Peng, Zicheng; Amakawa, Hiroshi; Burr, George S.; Lee, Shih-yu; Delong, Kristine L.; Elderfield, Henry; Shen, Chuan-chou.
The Intertropical Convergence Zone (ITCZ) encompasses the heaviest rain belt on the Earth. Few direct long-term records, especially in the Pacific, limit our understanding of long-term natural variability for predicting future ITCZ migration. Here we present a tropical precipitation record from the Southern Hemisphere covering the past 282,000 years, inferred from a marine sedimentary sequence collected off the eastern coast of Papua New Guinea. Unlike the precession paradigm expressed in its East Asian counterpart, our record shows that the western Pacific ITCZ migration was influenced by combined precession and obliquity changes. The obliquity forcing could be primarily delivered by a cross-hemispherical thermal/pressure contrast, resulting from the...
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Ano: 2015 URL: https://archimer.ifremer.fr/doc/00334/44545/44258.pdf
Registros recuperados: 5
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