SEASONAL PUMPING OF LOW-SALINITY ARCTIC WATER INTO BAFFIN BAY INFERRED FROM REMOTELY-SENSED IMAGES OF SEA ICE: IMPLICATIONS FOR ICE-AGE INITIATION

In November, sea-ice coverage of Baffin Bay begins at the mouth of Lancaster sound, the main channel to the Arctic Ocean in the far northwest corner of the bay. The sea ice extends progressively across the bay and southward, covering the bay south beyond Disco Island by mid January. In late spring an area of open water first appears paradoxically at the northern end and enlarges southward, with the last sea-ice remnant persisting in the midsection of the bay until mid July. This paradox is explained by seasonal trends of atmospheric pressure over the thick polar pack ice. In the fall polar air pressure rises as the pack-ice surface cools, forcing water from the Arctic Ocean through Lancaster Sound, and sliding it out over the denser water of the bay. Stratification is necessary to freeze sea ice, which freezes first where the stratification is greatest near the mouth of the sound. In the spring the polar temperature rises, atmospheric pressure falls, and flow through the sound reverses. Water entering the sound is then less stratified and is drawn from nearby deeper and warmer levels. Consequently, the ice near the sound melts first and the open water area expands from there. Today the thick pack ice is diminishing and covers only half the Arctic Ocean. In another 25 years it may be gone and only thin first-year polar ice will form. Greater heat transfer from the sea to the atmosphere will then prevent low polar temperatures and high pressures, thus greatly diminishing the inflow of polar water into Baffin Bay. The dominant saline West Greenland current will then increase the surface salinity, and deep water may form. The resulting conveyor-belt would keep the bay ice-free, providing an abundant source of moisture for major glaciation on Baffin Island and Quebec.