Abstract
A significant reduction in the Atlantic Meridional Overturning Circulation and rapid northern Hemisphere cooling 8200 years ago have been linked to the final melting of the Laurentide Ice Sheet. Although many studies associated this cold event with the drainage of Lake Agassiz-Ojibway, recent model simulations have shown that the Hudson Bay Ice Saddle collapse would have had much larger effects on the Atlantic Meridional Overturning Circulation than the lake outburst itself. Based on a combination of Mg/Ca and oxygen isotope ratios of benthic foraminifera, this study presents the first direct evidence of a major Labrador shelfwater freshening at 8.5 ka BP, which we associate with the Hudson Bay Ice Saddle collapse. The freshening is preceded by a subsurface warming of the western Labrador Sea, which we link to the strengthening of the West Greenland Current that could concurrently have accelerated the ice saddle collapse in Hudson Bay.
Highlights
A significant reduction in the Atlantic Meridional Overturning Circulation and rapid northern Hemisphere cooling 8200 years ago have been linked to the final melting of the Laurentide Ice Sheet
The disturbance of North Atlantic Deep Water formation, in turn, has been linked to a severe freshening caused by the sudden outburst of ice-dammed proglacial Lake Agassiz-Ojibway[9] (LAO), which formed along the southern margin of the Laurentide Ice Sheet (LIS) during the terminal stage of the last deglaciation over North
Sedimentological changes associated with the Lake Agassiz-Ojibway9 (LAO) drainage event are determined by characteristic peaks in both redness of bulk sediment and relative content of detrital carbonate inferred from elemental Ca/Sr ratios measured by X-ray fluorescence (XRF) core scanning
Summary
A significant reduction in the Atlantic Meridional Overturning Circulation and rapid northern Hemisphere cooling 8200 years ago have been linked to the final melting of the Laurentide Ice Sheet. A sediment core from the central Labrador Shelf recorded a surface water freshening around 8.2 ka BP based on a reduction in the Mg/Ca temperature-adjusted planktic foraminiferal δ18O signature[36].
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