By using a coupled ice-ocean model, the seasonal extent of the sea ice cover in the Sea of Okhotsk was examined. The model results show that the sea ice at the ice edge is advected southward along Sakhalin Island with a mean velocity of 0.31m/s into ocean water with temperatures above freezing. As a result, even in mid-winter, a large amount of ice melting occurs around the edge. It results in temperature decrease in the surface mixed water. During the 1993--1994 winter, the total volume ratio of ice melting to ice production is estimated at 0.76. The negative latent heat flux from the ice melting is nearly comparable to the total atmospheric heat flux around the ice edge. Furthermore, the meltwater supply to the surface layer is estimated to be approximately 3.5 times the annual Amur River inflow. Thus it is concluded that the ice melting around the extending ice edge is a significant factor for the heat and salt balance between the sea ice and the surface mixed layer and plays an important role in the maintenance of the large seasonal sea ice extent in the Sea of Okhotsk.