Measurements of the summer surface heat budget of the Northeast Water Polynya in 1992

Abstract

A research cruise of the United States Coast Guard Cutter Polar Sea to the Northeast Water Polynya (NEWP), off the eastern coast of Greenland (77–81°N, 6–17°W), was made from mid‐July to mid‐August of 1992 (NEWP '92) as the first field component of the multidisciplinary study of a high‐Arctic polynya. Instruments to measure the components of the surface heat budget of the polynya were installed on a foremast at the bow of the ship. Measurements of apparent wind speed and direction, air temperature and humidity, long‐ and short‐wave downwelling radiation were made, together with sea surface temperature. The surface heat budget of the polynya derived from these measurements is presented and is shown to be dominated by the net radiation, with a mean value of 133 W m−2, when calculated over the duration of the cruise. The short‐wave insolation was high during the days with clear skies, reaching over 500 W m−2 at noon and dropping to about 75 W m−2 during the sunlit, polar night, with a mean value of 197 W m−2. In comparison, the mean value of the incident long‐wave radiation is 267 W m−2. In general, the turbulent fluxes were negligible. The measured heat budget is compatible with the observed thermal structure in the surface layers of the polynya and the presumed ice melt during the summer season.