Numerical experiments of air–ice drag coefficient and its impact on ice–ocean coupled system in the Sea of Okhotsk

Abstract

Sensitivity study of the air–ice drag coefficient CDai is presented with an ice–ocean coupled model for the Sea of Okhotsk. The CDai × 103 value is varied from 2 to 5 based on the direct measurements in the region. The maximum volume transport of the East Sakhalin Current and the mean sea ice velocity were intensified as CDai increased. The sensitivity experiment with the ice–water drag coefficient CDiw showed that the East Sakhalin Current volume transport is hardly affected by CDiw but significantly intensified by CDai. While the ice drift in the off-ice-edge direction was intensified by the increase in CDai and the decrease in CDiw, the ice edge location was nearly unchanged. This was due to melting caused by the relatively warm water inflow from the North Pacific. That is, sea ice extent in the region is strongly influenced by melting caused by a large ice–ocean heat transfer. In the active melting regions, the ice–ocean heat transfer of more than 100 W/m2 occurred even in mid-winter. This is the same order as the cooling by air in winter, and a heat insulation capacity of sea ice is weakened in such regions.