Atmospheric-driven state transfer of shore-fast ice in the northeastern Kara Sea

Frequencies of observed occurrences of shore-fast ice in the northeastern Kara Sea for each month during 1953-1990 reveal a multimodality of shore-fast ice extent in late winter and spring. The fast ice extent exhibits mainly three different configurations (modes) associated with the regional topography of coasts and islands. These modes show fast ice areas equal to approximately 98 +/- 6, 122 +/- 6, and 136 +/- 8 1000 km(2). Analysis of the time series of fast ice extent shows that favorable conditions for expansion of fast ice seaward in winter and spring are met if the atmospheric circulation over the northeastern Kara Sea is controlled by the Arctic high, resulting in offshore winds and a significant (up to 6 degrees C) decrease of the monthly mean surface air temperature. In contrast, the penetration of the Icelandic low into the Kara Sea, accompanied by Arctic cyclones coming from the west, is responsible for the partial breakup and decrease of fast ice extent in winter or spring.