Reconstructing sea surface temperature and salinity using δ18O and alkenone records

International audienc

A Model Study of the Atlantic Thermohaline Circulation During the Last Glacial Maximum

STABLE isotope measurements in deep-sea sediment cores have indicated that the Atlantic thermohaline circulation experienced significant changes during the last glacial maximum: the North Atlantic Deep Water (NADW) was shallower than today and the Antarctic Bottom Water (AABW) penetrated much farther north(1-6). Numerical ocean models have, so far, been unable to simulate these circulation changes realistically(7). Here we show that a zonally averaged, three-basin ocean model, driven by glacial boundary conditions(8-10), reproduces the main trends of the geochemically constrained glacial Atlantic circulation. In addition, we provide quantitative estimates of the meridional water transport during glacial times. Our results suggest that the glacial production of AABW was slightly higher than at present, whereas that of NADW was reduced by similar to 40%, resulting in an intermediate circulation cell which closed within the Atlantic basin. We also show that the strength of the Atlantic conveyor belt strongly depends on the surface density contrast between the high latitudes of the Northern and Southern hemispheres

High latitude deep water sources during the last glacial maximum and the intensity of the global oceanic circulation

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The timing of the last deglaciation in North Atlantic climate records

International audienc

Recent advances in isotopes as palaeolimnological proxies

Isotope geochemistry is an essential part of environmental and climate change research and over the last few decades has contributed significantly to our understanding of a huge array of environmental problems, not least in palaeolimnology and limnogeology. Here we describe some of the recent developments in the use of stable isotopes in palaeo-lake research. These are: better preparation, analysis, and interpretation of biogenic silica oxygen and silicon isotopes; extraction and characterisation of specific compounds such as leaf waxes and algal lipids for isotope analysis; determining the excess of 13C–18O bonds in clumped isotopes; and the measurement of multiple isotope ratios in chironomid chitin. These advances have exciting prospects and it will be interesting to see how these techniques develop further and consequently offer a real advancement in our science over the next decade