HUDSON BAY-HUDSON STRAIT JOKULHLAUPS AND HEINRICH EVENTS - A HYPOTHESIS

Abrupt temperature changes in the northern North Atlantic occurred fre quently throughout the last glaciation as shown by proxy records from Greenland ice-cores, deepsea cores, and Norway speleothems. Many of th ese variations occurred in irregular sawtooth cooling cycles which som etimes ended with the deposition of thick layers of ice-rafted debris (IRD) in the deep ocean that are known as Heinrich events. The litholo gies of most of the IRD deposits are consistent with widespread surges of the Laurentide Ice-Sheet that may have resulted from the accumulat ion of deformable sediments in portions of the ice-sheet bed. An alter native conceptual model proposed here to explain the sawtooth coolings and the surges involves repetitive jokulhlaups from a Hudson Bay lake dammed by ice at the mouth of Hudson Strait. The slow sawtooth coolin gs may be explained by storm track diversion due to progressive covera ge of the lake by icebergs, and the surges by abrupt losses of water p ressure and buttressing ice-shelves at all ice-sheet fronts in the lak e when the ice-dams failed.