An analysis of first-year fast sea ice during the melt season has been made by using surface measurements and aircraft radar and photographic imagery obtained during a field study near Prince Patrick Island in the Canadian Archipelago from June 13 to July 13, 1982, and satellite imagery from Landsat and Seasat. Distinct changes observed in the properties of the snow layer and the sea ice were a temporary increase in small-scale roughness caused by formation of nodules of ice at the snow/ice interface; extensive snow melt and surface flooding; development of surface water drainage networks and low topography around fractures and seal breathing holes; and a rapid draining of much of the surface water. From the extensive salinity profiles obtained, two zones of rapid desalination in the first-year ice were observed: one zone extending from the air/ice interface downward toward the center of the ice sheet that resulted from surface warming and drainage of the surface melt water through the ice and the other zone extending from the sea/ice interface upward toward the center of the ice sheet that resulted from heating and separation of seawater and ice caused by a layer of low-salinity meltwater beneath the ice formed from surface meltwater runoff. Aircraft radar imagery detected changes in the amount of surface water and in the development of topography surrounding drainage features. Similar changes were detected in coincident Landsat multispectral scanner (MSS) imagery of the study area and in SEASAT radar imagery and Landsat MSS imagery of the Prince of Wales Strait from July 1978.