RELATIONSHIP BETWEEN THE UPPER OCEAN AND SEA-ICE DURING THE ANTARCTICMELTING SEASON

During the Antarctic ice-melting season, high-resolution sea ice data were collected with the video monitoring system aboard the icebreaker Shirase along with the monitoring of temperature and salinity in the u pper ocean. On the basis of these data, relationships among sea ice co ncentration, temperature, and salinity are investigated. In the ice in terior region away from the ice-free ocean, ice concentration is negat ively correlated with temperature and positively correlated with salin ity for the spatially averaged data, which suggests chat the local bal ances of heat and salt nearly hold in a bulk area. At the ice margin, ice concentration is negatively correlated with both temperature and s alinity, suggesting that the local balances are overwhelmed by the eff ects of ice advection. The expendable bathythermograph profiles at the ice margin also show that considerable amount of sea ice was advected into the ice-free ocean and subsequently melted there. It is pointed out that a polynya works as an ''ice-melting factory'' in summer; it a bsorbs solar radiation during the period of opening, and then melts th e ice advected there. From a heat budget analysis and ocean structure in the melting season, we propose a simple ice-upper ocean coupled mod el in which sea ice melts on the bottom and lateral faces with the hea t source supplied to the open water area by solar radiation. The relat ions among ice concentration, temperature, and salinity derived from t he model are consistent with the observed relations. The analytic solu tion for the no lateral melting case shows that the concentration-temp erature relation converges to a certain asymptotic curve with time, wh ich explains that the temperature-concentration plot shows a similar r elation for any region. Dependence of the relations among ice concentr ation, temperature, and salinity on the spatial scale is also discusse d.