Isforholdene i Barentshavet og vest av Spitsbergen. En oversikt

Abstract

The purpose of the present paper is to review our knowledge of the sea ice conditions of the Barents Sea and the area west of Spitsbergen and is mainly based on available literature. The variations of the sea ice conditions may be regarded to be of three different types. Short-term variations take place within periods from a few hours to about one month. On some occasions the position of the ice border during one week can vary more than 100 km. The seasonal variation of the sea ice extension is, in its broad features, similar from one year to another. Nevertheless, great interannual variation in the position of the ice border may occur. In some months these variations exceed 500 km. There seems to be no connection between freezing in winter and melting in summer. Cyclic variations in the ice conditions of periods between 3-5 years have been proposed. Also a period of 11 years, which coincides with the solar activity cycle, has been put forward. However, the verification of these periods is not convincing. In addition long-term trends are observed. The main characteristic feature of the sea ice distribution is caused by permanent warm and cold currents in the area. There also seems to be a connection between the heat content of the Atlantic water which enters the Barents Sea, and the extension of the ice in winter. How far the ice withdraws in summer depends on local meteorological conditions only. On the west coast of Spitsbergen, however, there appears to be a connection between extreme hydrographic situations and extremes in distribution of ice also in the summer. Considering the meteorological conditions, most attention has been focussed on the effects of air temperature, air pressure and prevailing winds. Some authors have found corresponding variations in air temperature and ice conditions, while others have dealt with the relationship between air pressure differences and ice extension. These studies indicate a correspondance between the sea ice conditions and the atmospheric circulation. However, variations in the atmospheric circulation also affect the intensity of ocean currents and vice versa. This intercorrelation complicates the task of identifying the most significant factors influencing the variations of the sea ice.