THE INFLUENCE OF RIVER DISCHARGE ON THE THAWING OF SEA-ICE, MACKENZIE RIVER DELTA - ALBEDO AND TEMPERATURE ANALYSES

Multi-temporal satellite images, field observations and field measurements were used to investigate the mechanisms by which sea ice melts offshore from the Mackenzie River Delta. Satellite data recorded between April and August 1986 were corrected to a map projection and calibrated such that albedo and temperature values could be compared. Three stages in the melting of sea ice were identified: flooding (overflows), insolation and melting by warm river water. The albedo values of overflows were as much as 1/7 that of ice values while the albedo of ice decreased by 1/3 over the summer. Approximately two weeks after the overflows develop, sea surface temperatures rise as the river-discharge peaks and becomes the dominant source of energy. By this process, ice removal in the delta regime is initiated two months earlier than adjacent coasts with minimal runoff. However, the net result is only a two-week acceleration of ice removal in the delta region.