We report a new time series of stable isotopic values for the past 12 ka measured in two species of shallow-water marine bivalves collected from raised marine deposits along the coast of Arctic Canada. Each sample (n = 60) had been radiocarbon dated previously. The results indicate that between 11.8 and 10 ka the δ18O of the shells ranged between 0.25???? and -6????, but values increased after 9 ka as the flux of meltwater to the Arctic Ocean decreased and as the Canadian Arctic channels opened to allow the present surface circulation to become established. Prior to about 9 ka, glacial meltwaters from the northern margin of the Laurentide Ice Sheet must have been entrained in the surface waters of the Arctic Ocean and directed southward to the North Atlantic through Fram Strait. This source of meltwater must be included in late Quaternary models of forcing of the North Atlantic thermohaline circulation. Glacial isostatic uplift of the sills within the Canadian Arctic channels implies that outflow through Fram Strait increased during the Holocene.

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