HR: 11:35h
AN: PP12A-06    [Abstracts]
TI: The pathway and impact of fresh water discharge through Hudson Strait 8200 years ago
AU: * Winsor, P
EM: pwinsor@whoi.edu
AF: Woods Hole Oceanographic Inst., 360 woods Hole Rd, Woods Hole, MA 02543
AU: Chapman, D C
EM: dcahpman@heaven.org
AF: Woods Hole Oceanographic Inst., 360 woods Hole Rd, Woods Hole, MA 02543
AU: Keigwin, L
EM: lkeigwin@whoi.edu
AF: Woods Hole Oceanographic Inst., 360 woods Hole Rd, Woods Hole, MA 02543
AU: Lentz, S J
EM: slentz@whoi.edu
AF: Woods Hole Oceanographic Inst., 360 woods Hole Rd, Woods Hole, MA 02543
AB: The strongest climate cooling event in the last 10,000 years occurred about 8200 years ago (8.2 ka). Numerous papers hypothesize that this abrupt cooling was caused by the drainage of glacial Lake Agassiz that covered much of northern Canada. The basic premise, mainly based on numerical modelling studies, is that the large volume of freshwater from Lake Agassiz spread over the northern North Atlantic forming a fresh, buoyant surface layer that inhibited the normal formation and sinking of dense water that drives the large-scale meridional overturning circulation (MOC) in the ocean. The reduced poleward heat transport due to the weakening of the MOC caused the observed abrupt cooling and associated climate changes in the time range 8400 to 8000 yrs BP. Here we show that the freshwater released from Lake Agassiz just prior to the '8.2 ka event' probably did not spread offshore into the northern North Atlantic, but instead formed a narrow buoyant current that flowed southward along the coast. This result and paleo-oceanographic data indicate that most of the low salinity water probably did not reach the open ocean until mixing in the slope water system between Newfoundland and Cape Hatteras. The absence of clear oxygen isotope evidence for low salinity anywhere else in subpolar waters suggests that the freshwater signal from the discharge may have been too weak by the time it reached convection sites in the Nordic Seas to have affected the MOC.
DE: 0429 Climate dynamics (1620)
DE: 1821 Floods
DE: 3002 Continental shelf and slope processes (4219)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005