A mesoscale cyclone over the Fram Strait and its effects on sea ice

The ice export from the Arctic Ocean through the Fram Strait into the Atlantic Ocean is steered by atmospheric processes on the large scale as well as on the local scale. A case study of a mesoscale cyclone over the Fram Strait and its effects on the sea ice drift is presented. The cyclone developed on March 13, 1993, at the ice edge of the Greenland Sea and moved northward over the ice and over the position of the research icebreaker Polarstern and an array of six meteorological ice buoys. The cyclone had a radius of about 150 km and was essentially restricted to the lowest 2 km of the atmosphere. Near the surface the temperature difference between the air in the warm sector and the surrounding cold air was 25 K resulting in a pressure difference of about 15 hPa between center and the surrounding with low-level wind speeds of up to 20 m/s. The passage of the cyclone caused a full loop of the ice drift otherwise oriented from northeast to southwest. The ratio of ice drift speed to wind speed, increased from 5 % before to 9 % after the passage. Extreme values of ice deformation and large variations of the ice strain rate tensor occurred during the cyclone passage. It is concluded that passing cyclones can affect the sea-ice drift through the bottleneck of the Fram Strait and may have integral effects on larger time scales and space scales.