MILLENNIAL-SCALE FLUCTUATIONS IN NORTH-ATLANTIC HEAT-FLUX DURING THE LAST 150,000 YEARS

Surface water and deep ocean palaeoclimate records obtained from North Atlantic core SU90-03 (40 degrees N, 32 degrees W) exhibit pronounced fluctuations at sub-orbital time scales. Surface temperature variabil ity in the mid-latitude Atlantic over the last 150 kyr is dominated by forcing at precession (21 kyr) and semi-precession harmonics (11 kyr) . Abrupt changes in sea surface temperatures show that the northward t ransport of heat by the North Atlantic Current was curtailed during ic e rafting events. Sea surface temperatures were about 12 degrees C col der than modern values during the most intense cooling episodes associ ated with major ice rafting events (Heinrich events i, 4, 6 and 11) an d 10 degrees C below modem values during the later part of isotope sta ge 3 (40-30 ka). During these cold intervals, the North Atlantic Curre nt was displaced to south of 40 degrees N as the cold meltwaters penet rated southwards into what is now the subtropical ocean. These changes in surface ocean heat exchange were most probably allied to a latitud inal migration and increase in zonality of atmospheric circulation pat terns. Concurrent shifts in IRD concentration, sea surface temperature s and benthic delta(13)C values provide evidence of coupling between s ea surface processes and the deep-water circulation, and suggest that decreases in surface temperature and salinity during ice rafting event s culminated in a significant reorganisation of North Atlantic Deep Wa ter production. (C) 1998 Elsevier Science B.V. All rights reserved.