FRESHENING OF THE UPPER OCEAN IN THE ARCTIC - IS PERENNIAL SEA-ICE DISAPPEARING

During the Surface Heat Budget of the Arctic (SHEBA) deployment in Oct ober, 1997, multiyear ice near the center of the Beaufort Gyre was ano malously thin. The upper ocean was both warmer and less saline than in previous years. The salinity deficit in the upper 100 m, compared wit h the same region during the Arctic Ice Dynamics Joint Experiment (AID JEX) in 1975, is equivalent to surface input of about 2.4 m of fresh w ater. Heat content has increased by 67 MJ m(-2). During AIDJEX the cha nge in salinity over the melt season implied melt equivalent to about 0.8 m of fresh water. As much as 2 m of freshwater input may have occu rred during the 1997 summer, possibly resulting from decreased ice con centration from changes in atmospheric circulation early in the summer , in the classic albedo-feedback scenario. Unchecked, the pattern coul d lead to a significantly different sea-ice regime in the central Arct ic.