Area balance of the Arctic Ocean perennial ice zone: October 1996 to April 1997

Abstract

We use National Aeronautics and Space Administration scatterometer (NSCAT), RADARSAT, and ice motion data to examine the perennial ice zone (PIZ) of the Arctic Ocean between October 1996 and April 1997. The PIZ is identified by a simple backscatter‐based classification of the gridded NSCAT backscatter fields. The area of the PIZ at the beginning of October occupies an area of 5.32 × 106 km2, ∼76% of the Arctic Ocean. By the first of May, only 4.54 × 106 km2 of that area remains, a decrease of 0.78 × 106 km2 over the 7‐month period. This area loss can be explained almost entirely by ice export. Over this period the total area flux of sea ice through Fram Strait, estimated using satellite passive microwave ice motion, is 0.80 × 106 km2 or 12% of the Arctic Ocean. Approximately 0.70 × 106 km2 or 88% of the exported area is from the PIZ. Nares Strait outflow is small at 34,000 km2 and is estimated by summing the high backscatter areas exported into northern Baffin Bay. After accounting for the outflow through the Fram and Nares Straits an unexplained residual of 46,000 km2 remains. We attribute this residual to errors in our estimation process, the unaccounted for ice flux through the Canadian Archipelago, and the net divergence and convergence of the PIZ over the period. Our interpretation of the radiometry seems to be sound on the basis of the area balance arguments provided here. This study shows that (1) the PIZ converage of the Arctic Ocean can be derived from NSCAT backscatter fields and (2) the decrease in PIZ area over the winter is a good estimate of the PIZ net ice area exported through Fram Strait.