Abstract
The changing of sea ice in the Arctic and Antarctic has been monitored by satellite on board microwave radiometry since 1978. Understanding the variability of the sea ice brightness temperature is important for accurately estimating the sea ice concentration. Summer sea ice is wet due to the effects of air temperature and solar radiation. Melting water causes drastic changes to the brightness temperature. The purpose of this study is to clarify the brightness temperature variability of multi-year ice during the melting season. We observed multi-year ice offshore at Syowa Station, Antarctica. The brightness temperature was measured from the snow surface, snow pack, and multi-year ice surface. The measurements show that the brightness temperature from the multi-year ice surface had great variability depending on the different surface conditions. However, the brightness temperature from the snow pack remained constant due to the influence of wet snow. For this reason, microwave radiation below the wet snow cannot be transmitted to the upper layer. The brightness temperature of the snow surface is high when the surface is covered by wet snow. By contrast, when the surface is covered by dry snow, the brightness temperature of the snow surface is different depending on the optical thickness of the dry snow. When wet snow is included in the snow pack on multi-year ice, the brightness temperature during the melting season depends on whether the snow surface is dry snow or wet snow.
