HR: 1340h
AN: PP13B-1267    [Abstracts]
TI: The Antarctic Intermediate Water During the Younger Dryas Time Period
AU: * Cortijo, E
EM: Elsa.Cortijo@lsce.ipsl.fr
AF: LSCE (CNRS-CEA-UVSQ), Domaine du CNRS, Avenue de la Terrasse, Gif-sur-Yvette cedex, 91198, France
AU: Michel, E
EM: Elisabeth.Michel@lsce.ipsl.fr
AF: LSCE (CNRS-CEA-UVSQ), Domaine du CNRS, Avenue de la Terrasse, Gif-sur-Yvette cedex, 91198, France
AU: Labeyrie, L
EM: Laurent.Labeyrie@lsce.ipsl.fr
AF: LSCE (CNRS-CEA-UVSQ), Domaine du CNRS, Avenue de la Terrasse, Gif-sur-Yvette cedex, 91198, France
AU: Turon, J
EM: jl.turon@epoc.u-bordeaux1.fr
AF: EPOC, Universit\´{e} de Bordeaux 1, Avenue des Facult\´{e}s, Talence cedex, 33405, France
AU: Duplessy, J
EM: Jean-Claude.Duplessy@lsce.ipsl.fr
AF: LSCE (CNRS-CEA-UVSQ), Domaine du CNRS, Avenue de la Terrasse, Gif-sur-Yvette cedex, 91198, France
AB: Reorganization of intermediate and deep water masses during the last deglaciation is still a matter of debate. Two radiocarbon dated cores located in the southern Indian Ocean (core MD 79-257, 20°24' S ; 36°20' E ; 1262 m water depth and core MD 84-527 43°49'3 S ; 51°19'1 E ; 3269 m water depth ) were studied to reconstruct the physical characteristics (salinity and temperature) of the intermediate water and of the surface waters during the deglaciation. We used micropaleontologic transfer functions and the oxygen isotope of planktonic foraminifera to reconstruct Sea Surface Temperature and estimate the surface water oxygen isotopic composition (a proxy for salinity) in the area of intermediate water formation. We measured the oxygen isotopic composition of benthic foraminifera to estimate the temperature and salinity of the intermediate water mass near 20° S at 1260 m depth. Our data show that the Antarctic Intermediate Water in the Indian Ocean was saltier and warmer than the present during the Younger Dryas, between 12,5 and 11,5 kyr BP. The presence of warm saline surface waters near 44°S implies a southward migration of the subtropical front in the Southern Ocean compared to the present during the Younger Dryas. This warming may be explained by an enhanced inflow of warm saline waters carried by the retroflexion of the Agulhes Current following the southern shift of the Intertropical Convergence Zone during cold events in the North. A similar warming has been recorded in the Vostok and Dome C Antarctic ice cores during the Younger Dryas, which appears as a warm event by contrast with the climatic record of the North Atlantic. The opposite behaviour of Northern and Southern high latitudes suggests that the sea saw mechanism also affected the intermediate circulation at low latitudes.
DE: 4900 PALEOCEANOGRAPHY (0473, 3344)
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4938 Interhemispheric phasing
DE: 4954 Sea surface temperature
DE: 4962 Thermohaline
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting