Changes in North Atlantic deep-water formation associated with the Dansgaard-Oeschger temperature oscillations (60-10 ka)

We closely compared high-resolution delta(13)C records of benthic foraminifera Cibicides wuellerstorfi, a proxy for deep-water ventilation, with the Dansgaard Oeschger temperature oscillations. Our results reveal different perturbations of deep-water formation in the North Atlantic Ocean associated with the millennia I-scale climate oscillations during the last glacial period. The cooling episodes associated with the drastic Heinrich events are related to large reductions of deep-water formation and a northward migration of C-13 depleted southern source deep waters to 62degreesN in the North Atlantic Ocean. The inter-Heinrich events which are correlated to the other cold stadials, are marked by significant changes of sea surface temperature around the Rockall Plateau, variations in the flux of icebergs to the North Atlantic Ocean but are not associated with such important reduction of deep-water formation. If changes in the thermohaline circulation (THC) are associated with these millennial-scale climatic oscillation they affect only the deeper water masses, below 2000 m, of the North Atlantic Ocean. We thus show that equivalent degree of cooling over Greenland is obtained with different perturbations of deep-water formation. Our results either question the role of the THC as the unique explanation for these millennial-scale climate oscillations, or call upon an amplifying mechanism not yet taken into account. (C) 2002 Elsevier Science Ltd. All rights reserved.