An analysis of the dissolution of ice in Nares Strait using AVHRR imagery

The North Water Polynya is the largest polynya in the Canadian Arctic. Its northern boundary is defined by a blockage, or ice bridge, that spans Smith Sound. The maintenance of the ice bridge, and the polynya itself, is conti ngent upon the southward flow of ice from the Lincoln Sea through Nares Str ait. This paper analyzes the dissolution of ice in Nares Strait using Advan ced Very High Resolution Radiometer (AVHRR) data. From March to August 1998 , 1440 images were downloaded by a satellite receiver at Canadian Forces St ation (CFS) Alert on the northern tip of Ellesmere Island. A preliminary ev aluation of the data included a visual assessment of over 300 cloud-free im ages. Of most interest were 42 images that revealed a rapid dissolution of ice in Nares Strait during mid-June. In a four-day span the area of open wa ter in Nares Strait increased from 400 km(2) to 1200 km(2). Subsequent anal ysis of selected scenes included the application of both a sea and ice surf ace temperature algorithm. Based on the satellite imagery and archived weat her data from CFS Alert, the ice in Nares Strait initially began to weaken and break-up due to in situ melting. The significant reconfiguration of ice observed during mid-June was the result of high winds funnelling southward through the channel.