Passive microwave observations of the Northeast Water Polynya interannual variability: 1978–1994

Abstract

Abstract A description of the seasonal cycle and interannual behavior of the Northeast Water (NEW) Polynya based upon a series of daily total ice concentrations derived from passive microwave satellite observations (1978–1994) is presented. The integrated ice-free areal extent within the region extending from 76 to 82°N and from the coast of northeast Greenland to the shelf break is used as an indication of the opening of the NEW Polynya. The Polynya stays open from the beginning of May to the end of September. The summer maximum total water (TW) area ranges from a minimum 59,000 (in 1992) to a maximum of 120,000 km2 (in 1985) and the date of maximum opening from the beginning of July to the end of September. The largest values of TW during summer are observed for 1985, 1990 and 1991 and are accompanied by the appearance of a secondary opening to the south. In contrast, the smallest TW's that occurred in 1987, 1989 and 1992, exhibit only a northern cell. Monthly averages of heat budget, cloud cover, air temperature, and resultant vector wind are analyzed in order to explain the observed variations of TW in the NEW Polynya. It is found that the variations of TW are due to the heat budget which, for the pentad March 1985-February 1990, explains 86% of the observed variance in TW with a lag of one month. This lag indicates that the response of the Polynya to the thermal forcing is not dominated by higher frequency variability. Utilizing this relationship and the TW for the summers of 1992 and 1993, the potential amount of melt water was estimated assuming all the heat was available for melting. The values of 51 and 79 cm, are in good agreement with independent estimates of seasonal melting based on hydrography. The effects of wind are not easily decoupled from those of the heat budget making it difficult to establish more precisely the extent to which the Polynya may be considered a closed system.