Abstract
Abstract. This study investigates the impact of cyclones on the Arctic Ocean sea ice for the first time in a statistical manner. We apply the coupled ice–ocean model NAOSIM which is forced by the ECMWF analyses for the period 2006–2008. Cyclone position and radius detected in the ECMWF data are used to extract fields of wind, ice drift, and concentration from the ice–ocean model. Composite fields around the cyclone centre are calculated for different cyclone intensities, the four seasons, and different sub-regions of the Arctic Ocean. In total about 3500 cyclone events are analyzed. In general, cyclones reduce the ice concentration in the order of a few percent increasing towards the cyclone centre. This is confirmed by independent AMSR-E satellite data. The reduction increases with cyclone intensity and is most pronounced in summer and on the Siberian side of the Arctic Ocean. For the Arctic ice cover the cumulative impact of cyclones has climatologic consequences. In winter, the cyclone-induced openings refreeze so that the ice mass is increased. In summer, the openings remain open and the ice melt is accelerated via the positive albedo feedback. Strong summer storms on the Siberian side of the Arctic Ocean may have been important contributions to the recent ice extent minima in 2007 and 2012.
Highlights
Arctic sea-ice extent and thickness have undergone a significant decline in the last decade (Stroeve et al, 2012) with the latest record sea-ice extent minimum in September 2012
Cyclone position and radius detected from the ECMWF sea-level pressure were used to extract the local fields of wind, ice drift, and concentration within twice the cyclone radius for a time interval from 2 days before to 5 days after the cyclone passage
The cyclone impact is quantified by the drift-wind ratio, the deviation angle, and the change of ice concentration
Summary
Arctic sea-ice extent and thickness have undergone a significant decline in the last decade (Stroeve et al, 2012) with the latest record sea-ice extent minimum in September 2012. Brümmer: Cyclone impact on sea ice in the central Arctic Ocean measurements Maslanik and Barry (1989) found for wintertime situations in the Canadian part of the central Arctic, that cyclones lead to reductions in sea-ice concentration and increased divergence of the sea-ice drift. Barry and Maslanik (1989) reported a reduction in sea-ice concentration in summer in the Canadian part of the Arctic, caused by cyclonic conditions in the wind field and the associated divergent and sheared ice drift. They found that fewer cyclones over the central Arctic Ocean in May, June, and July favour a low sea-ice extent at the end of the melt season They argue that fewer storms are associated with above-average sea-level pressure, strengthened anticyclonic winds, intensification of the transpolar drift stream, and reduced cloud cover, which all favor ice melt.
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