Paleoceanography and Paleoclimatology [PP]
PP44B MW:2002 ThursdayAdvances in Understanding Millennial-Scale North Atlantic Climate Variability During the Past 2 Ma II
Presiding: H Rashid, College of Marine Science, University of South Florida; J E Channell, University of
Florida PP44B-05
The Pleistocene Labrador Sea, northwest North Atlantic (IODP Sites 1302/03, 1305 and ODP Site 646) with highlights on warm interglacials
* de Vernal, A (devernal.anne@uqam.ca), GEOTOP-Universite du Quebec a Montreal, PO Box 8888, Montreal, Qc H3C 3P8, Canada Hillaire-Marcel, C), GEOTOP-Universite du Quebec a Montreal, PO Box 8888, Montreal, Qc H3C 3P8, Canada McKay, J), GEOTOP-Universite du Quebec a Montreal, PO Box 8888, Montreal, Qc H3C 3P8, Canada Romero, O), Instituto Andaluz de Ciencias de la Tierra (IACT-CSIC), Universidad de Granada, Granada, 18002, Spain Mayor, S), GEOTOP-Universite du Quebec a Montreal, PO Box 8888, Montreal, Qc H3C 3P8, Canada Satte, Y), GEOTOP-Universite du Quebec a Montreal, PO Box 8888, Montreal, Qc H3C 3P8, Canada Lamziouaq, R), GEOTOP-Universite du Quebec a Montreal, PO Box 8888, Montreal, Qc H3C 3P8, Canada Preda, M), GEOTOP-Universite du Quebec a Montreal, PO Box 8888, Montreal, Qc H3C 3P8, Canada Stevenson, R), GEOTOP-Universite du Quebec a Montreal, PO Box 8888, Montreal, Qc H3C 3P8, Canada Fagel, N), Departement de Geologie, Université de Liege BAT. B18 Argiles et paléoclimats, Liege, 4000, Belgium
Sites cored during expeditions 105 and 303 off southern Greenland (IODP 1305, ODP 646) and eastern Canada (IODP 1302/1303) are ideally located for documenting the climatic and glacial history of adjacent lands in addition of providing information on thermohaline conditions in the northwest North Atlantic, notably with regard to convection in the Labrador Sea. Multiproxy studies (stable isotopes, pollen, dinocysts, clay minerals, radiogenic isotopes, U-series) in Pleistocene sequences at Sites 646 and 1305 show that different conditions prevailed during each interglacial with respect to sea-surface conditions, deep-current, and/or terrestrial vegetation on adjacent lands. For example, clay mineral assemblages and Nd isotopes indicate that sedimentary supplies during the recent interglacials (marine isotope stages (MIS) 1, 5e, 7 and 9, notably) were very different than those of previous interglacial stages, which were characterized by a sedimentary source not yet identified, possibly related to soils developed over volcanic rocks from a largely deglaciated Eastern Greenland. Pollen analyses also suggest that dense vegetation with distinct characteristics developed over Greenland during some interglacials of the mid-Pleistocene when the Greenland ice sheet volume was significantly reduced. In particular, rich pollen assemblages dominated by spruce are recovered in sediments of MIS 11, which suggest the development of boreal forest vegetation on southern Greenland, then ice-free. In addition to analyses of long time series, special attention was paid to the last interglacial (MIS 5e) at Sites 1302/1303 and 1305, during which particular high sea-surface temperatures were recorded (up to 5° C warmer than present) in spite of the absence of Labrador Sea water formation. In addition, sedimentation rates during during MIS 5e and 11, when compared to those of MIS 1, as well as the corresponding isotopic composition of planktic and benthic foraminifers, lead to even question the contribution of Denmark Strait Overflow Water (DSOW) during these interglacials. The modern Atlantic meridional overturning, characterized by Labrador Sea Water formation, due to winter cooling and convection in this basin, and by intense DSOW formation, seems mostly exclusive to the present interglacial.
