Sea surface temperature variability during the last glacial-interglacial cycle: assessing the magnitude and pattern of climate change in the North Atlantic

Sea surface temperature and salinity estimates reconstructed using planktonic foraminiferal abundance and delta(18)O records from core SU90-03 (40 degrees N, 32 degrees W, 2475 m water depth) reveal large climatic fluctuations linked to major instabilities in Northern Hemisphere ice sheets over the last 150 000 years. Episodes of enhanced ice rafted detritus (IRD) input were accompanied by discrete temperature minima, representing coolings of between 4 and 8 degrees C, and reductions in surface salinity of up to 2.5-3.5 parts per thousand. Several additional cooling episodes of a similar magnitude were documented during intervals of low IRD input that appear to be synchronous, within the limits of dating, with ice rafting events spatially confuted to higher latitudes. Accelerator mass spectrometer C-14 dates for Heinrich events (H1 - 14.2 ka, H2 - 21.4 ka, H3 - 26.7 ka, H4 - 34.8 ka, H5 - 47.2 ka) obtained from core SU90-03 agree well with other published age estimates and suggest a contemporaneous pattern of climate change throughout the North Atlantic during the last glacial period. This interpretation is supported by a comparison of IRD and palaeotemperature records from DSDP site 609 and core SU90-03, which clearly shows that the major climatic fluctuations identified at high latitudes were transmitted toward the subtropics. However,C-14 dates suggest that ice rafting episodes may be diachronous to some extent. The northward migration of the polar front after the H1 event at 40 degrees N in the mid-Atlantic occurred at 14 ka, approximately 500 years earlier than along the Portuguese margin, where the southerly advection of polar waters persisted within eastern boundary current system. (C) 2000 Elsevier Science B.V. All rights reserved.