PHYSICAL, STRUCTURAL, AND ISOTOPIC CHARACTERISTICS AND GROWTH-PROCESSES OF FAST SEA-ICE IN LUTZOW-HOLM BAY, ANTARCTICA

A sea-ice/ocean study was conducted off Queen Maud Land and Enderby La nd, Antarctica, from 1990 to 1991 by the Japanese Antarctic Research E xpedition. Observations of multiyear land fast sea ice were made in Lu tzow-Holm Bay over a period of 2 years to determine the snow and ice c haracteristics and ice growth processes. The snow depth in the bay rea ched large values of 1.0 to 1.5 m during the winter season at offshore locations. From the analysis of ice thickness measurements, it is con firmed that the fast ice with deep snow cover grew little in winter bu t substantially thickened during the summer months. On the basis of ic e core structure, salinity, and stable isotopic composition, we conclu de that the summer growth was caused by upward growth at the top of th e ice to which snow ice and superimposed ice formation contribute. The se processes were the primary contributors to sea-ice growth and chara cteristics only where the snow accumulation was large. In areas of low snow accumulation, there was no surface growth. Superimposed ice form ation on sea ice in Antarctica has not been reported previously. Evide nce for snow cover melting, which is a prerequisite for superimposed i ce formation, was also found.