Mapping of sea ice production in the Arctic coastal polynyas

Abstract

High ice production in coastal polynyas over the continental shelves in the Arctic Ocean is responsible for the formation of cold saline water, which contributes to the maintenance of the Arctic Ocean halocline. The accurate detection of coastal polynyas, including an estimate of thin ice thickness, is essential for the estimation of sea ice production. This paper presents an algorithm that estimates thin ice thickness using Special Sensor Microwave/Imager (SSM/I) data in the Arctic Ocean. Detection and estimation of sea ice thicknesses of <0.15 m are based on the SSM/I 85 and 37 GHz polarization ratios (PR85 and PR37) through a comparison with sea ice thicknesses estimated from the advanced very high resolution radiometer (AVHRR) data in the three different Arctic coastal polynyas. Thus, for the entire Arctic Ocean, the algorithm can be used for the detection of coastal polynyas and for the estimation of sea ice production through combination with heat‐flux calculation. This study provides the first circumpolar mapping of sea ice production in coastal polynyas over the entire Arctic Ocean. High ice production is confined to the major Arctic coastal polynyas, with the highest ice production rate being in the North Water Polynya. This study also presents the interannual variability of sea ice production in the 10 major coastal polynyas from 1992 to 2007. In general, interannual variability in sea ice production has good correlation with polynya extent rather than surface air temperature. The mapping also provides surface heat‐ and salt‐ flux conditions in the ice‐covered region, which have not been well understood to date.