HR: 17:45h
AN: PP44B-08 INVITED    [Abstracts]
TI: Millennial-scale climate changes: linkages between low and high latitudes
AU: * Paul, A
EM: apau@palmod.uni-bremen.de
AF: Center for Marine Environmental Sciences (MARUM), University of Bremen, Leobener Strasse, Bremen, 28359, Germany
AU: Chiessi, C M
EM: chiessi@marum.de
AF: Center for Marine Environmental Sciences (MARUM), University of Bremen, Leobener Strasse, Bremen, 28359, Germany
AU: Dupont, L
EM: dupont@uni-bremen.de
AF: Center for Marine Environmental Sciences (MARUM), University of Bremen, Leobener Strasse, Bremen, 28359, Germany
AU: Mulitza, S
EM: smulitza@uni-bremen.de
AF: Center for Marine Environmental Sciences (MARUM), University of Bremen, Leobener Strasse, Bremen, 28359, Germany
AB: Millennial-scale climate changes in the North Atlantic realm are thought to be associated with a slowdown of the Atlantic Meridional Overturning Circulation (AMOC), a cooling of the North Atlantic Ocean and a warming of the South Atlantic Ocean (the "bipolar seesaw" hypothesis). A closer look at multi-proxy data from marine sediments off the coasts of tropical and subtropical South America and Africa reveals a more complex picture. During the Heinrich 1 and Younger Dryas events, the Sahel region suffered from draughts; precipitation decreased in northern South America (e.g.\ in the Cariaco Basin), while it probably increased in parts of Brazil. Furthermore, in the western South Atlantic Ocean, we found a large and abrupt warming only after the Heinrich 1 event, during the transition to the Bølling-Allerød period. We interpret our data with the help of an Earth-system model of intermediate complexity that includes a marine biogeochemical component as well as land-surface and vegetation components. With decreasing strength of the AMOC, evaporation decreases in the North Atlantic Ocean and increases in the South Atlantic Ocean, precipitation decreases over northwestern South America as well as central Africa, and the "plant-functional types"/biomes show a small southward shift in western Africa. At the same time, the east-west slope of the South Atlantic thermocline flattens, consistent with relatively cold central and intermediate waters in the western South Atlantic Ocean. Our aim is to elucidate the processes that cause abrupt climate change, through the analysis of linkages between low and high latitudes in terms of changes in the hydrological cycle and atmospheric dust transport.
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4904 Atmospheric transport and circulation
DE: 4962 Thermohaline
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting