ABSTRACT:

During the Seasonal Ice Zone Experiment (SIZEX) in the Barents Sea in February 1989 several grounded icebergs were observed directly from ship and helicopter and by airborne Synthetic Aperture Radar (SAR). Depending on the characteristics of the surrounding pack ice, the grounded icebergs can leave elliptic tracks in the pack ice caused by the tidal current. These tracks are readily observed in SAR images, regardless of weather and light conditions. Therefore the tracks can be used to identify the location of grounded icebergs. In some cases, during high internal ice stress, grounded icebergs do not leave any tracks in the ice, but can be identified in a SAR image by a wake of open water a few hundred meters downstream. From 1991 SAR will be installed in polar orbiting satellites and provide a method to monitor icebergs on regular basis in areas like the Barents Sea.

INTRODUCTION

Most of the icebergs in the Barents Sea originate from glaciers in the northeastern parts of Svalbard and in Franz Josef Land and drift south towards Bj0rn0ya. Year-round observations at the meteorological stations at Bj0rn0ya and Hopen show that icebergs occur frequently in the period from February to June. Maximum frequency observed at Hopen is in April with observations on 43% of the days based on data from 1970 to 1981 (Vinje, 1989). There is also a considerable interannual variability of iceberg occurrences, presumably due to the variation in surging activity of the glaciers from which the icebergs originate. Variations in the release of fast ice around the islands where calving occurs is another likely mechanism to regulate the number of icebergs which are transported away from the production area. The horizontal dimension of the icebergs range from more than 500 m to very small sizes.

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