THE EASTERN CANADIAN ARCTIC AT CA.6 KA BP - A TIME OF TRANSITION

The middle Holocene was a time of definite environmental transition in the Eastern Canadian Arctic. Based on several proxy indicators (polle n, diatoms, foraminifera, molluscs and nearshore sedimentation rates), it appears that a thermal maximum occurred around middle Holocene (6- 4 ka), several thousand years after the insolation maximum - a lag cau sed by the thermal inertia of the earlier massive ice sheet. Terrestri al records indicate that a warming began around 6 ka, both in the suba rctic (Labrador - Ungava) and on Baffin Island. Marine records, on the other hand, suggested major water structure changes around 6 ka both in the Northeastern Canadian Arctic and also along the East Greenland coast with evidence of a marine surface water temperature maximum at 8 ka. We hypothesize that the marine circulation changes, both along th e Baffin Island and along the East Greenland coasts, were primarily dr iven by glacio-isostatic uplift of the Arctic Channels. With the cessa tion of water flow of Atlantic (warmer) origin, and decrease in water volume from the deeper parts of the Arctic Ocean through the Arctic Ch annels, the export through the Fram and Denmark straits increased and the water column changed. Changes in the concentration and duration of sea ice along the eastern Canadian coast would have had important rep ercussions on the biota of the coastal marine and terrestrial ecosyste ms.