Journal of the Meteorological Society of Japan, 81, 4, 653-677., 2003

Surface Heat Budget of the Sea of Okhotsk during 1987-2001 and the Role of Sea Ice on it

K. I. Ohshima, T. Watanabe, and S. Nihashi
The surface heat flux over the Sea of Okhotsk has been calculated from 1987 to 2001 by bulk parameterizations using ECMWF, ISCCP, and GISST data, corrected by COADS data. Sea ice concentration and ice type are incorporated by using an SSM/I open water and thin-ice algorithm to better represent the sea ice conditions. The mean seasonal variation of the net heat flux, averaged over the entire Okhotsk Sea, ranges from a summer maximum of 158 W m-2 in June (a positive value indicates that the sea or sea ice gains heat form the air), to a winter minimum of -219 W m-2 in December. The seasonal geographic distribution of the net heat flux is determined mostly by turbulent (sensible and latent) heat flux. Because of the heat insulating effect of sea ice, the turbulent heat flux and accordingly the net heat flux has the largest variation in winter, particularly in the north region, reflecting the yearly difference of sea ice extent. The geographic distribution of the annual net heat flux shows a distinct contrast, significant cooling of the ocean in the north and net heating of the ocean in the south. This contrast is a result of heat transport by both sea ice and the southward East Sakhalin Current; sea ice formed by obtaining negative latent heat in the north is transported to the south, then it releases the negative latent heat by melting. The annual net heat budget is estimated to be -22 W m-2 averaged over the entire sea. The Okhotsk Sea loses heat to the atmosphere on an annual basis, although at least the order of 20 W m-2 error exists in the estimation. A trial was performed to estimate sea ice production using the heat budget calculation. The results suggest that most of the production occurs in open water and thin ice areas. The highest production area is located over the northwest shelf, within 100 km of the coast.