Journal of Physical Oceanography,  2004 (in press)

A simplified ice-ocean coupled model for the Antarctic ice melt season

Kay I. Ohshima and Sohey Nihashi
In the Antarctic Ocean, sea ice melts mostly by warming of the ocean mixed layer through heat input (mainly solar radiation) in open water area. We propose a simplified ice-upper ocean coupled model in which sea ice melts only by the ocean heat supplied from the air. The model shows that the relationship between ice concentration and mixed layer temperature converges asymptotically with time (CT-relationship), which agrees with observed CT-plots during summer in the sector 25o- 45o E. This relationship can be used for estimating the bulk heat transfer coefficient between ice and ocean by fitting to observations and a value of 1.2 10-4 ms-1 is obtained. The model shows that the ratio of the heat used for melting to the heat input through open water is inclined to be determined as a function of ice concentration. For typical conditions in the Antarctic ice melt season, the ratio ranges mostly between 0.7 and 0.9. When the model is extended to two-dimensions in the meridional direction, with the inclusion of wind forcing, it approximately reproduces the meridional retreat of the Antarctic sea ice. This two-dimensional model can describe the open water-albedo feedback effect, which partly explains the year-to-year variation of the sea ice retreat in the Antarctic Ocean.