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Insight into Freshwater Input to the North Atlantic Ocean

December 1, 2005

The strongest climate cooling event in the last 10,000 years occurred
about 8,200 years ago. Known as the 8.2 ka event, it was an abrupt
release of freshwater to the ocean as the superlake Agassiz drained
through Hudson Strait into the Labrador Sea. Numerical modeling studies
have suggested that the large volume of freshwater from Lake Agassiz
spread over the northern North Atlantic Ocean, 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. But there are problems with the coarse resolution of
previous numerical studies, which suggest the freshwater was added
directly to a large area of the northern North Atlantic. New studies by
WHOI scientists, using high-resolution numerical calculations, 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. 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.

PP12A-06   11:35h   The Pathway and Impact of Fresh Water Discharge through Hudson Strait 8200 Years Ago