PRELIMINARY RESULTS OF HYDROGRAPHY UNDER FAST ICE IN LUTZOW-HOLM BAY, ANTARCTICA IN 1990

Seasonal variations in water structure under fast ice in Lutzow-Holm Bay, Antarctica, were observed from April to December, 1990. Two warm and oxygen-poor waters were observed. One is warmer water with temperatures higher than 0℃, salinities of more than 34.6 and oxygen less than 6 ml/l, and is found in the bottom layer deeper than 700m in the Shirase Submarine Valley. The other is found in the upper layer with temperatures of -1.4∿ -1.5℃, salinities of around 34.2 and oxygen of 6.3-6.9ml/l. The origin of both waters is a blob of the Circumpolar Deep Water (CDW) drawn from offshore, and they are admixtures of CDW with overlying Winter Water in various proportions. Due to high density, the former is confined to the bottom layers of deep troughs; on the contrary, the latter with low density can migrate in the upper layer with the water circulation in the bay. In spring a cold and oxygen-rich water (T7.2ml/l) was observed at the intermediate depth of about 250m-350m near the top of the downslope of the submarine valley. It is probable that this water was formed by sea ice processes during winter