Characteristics and growth processes of sea ice in Lutzow-Holm Bay

Abstract

Observations of multiyear land fast sea ice were made in Lutzow-Holm Bay, Antarctica over a period of two years from 1990 to 1991 to determine the snow and ice characteristics and ice growth prowth processes. The snow depth in the bay reached remarkably high values of 1.0 to 1.5m during the winter season at offshore stations. From analysis of ice thickness measurements, it is confirmed that fast ice with deep snow cover shows little growth during winter but substantially thickens during the summer months. On the basis of ice core structure, salinity and stable isotopic composition, it is concluded that the sea ice grows not downward as in ordinary growth but upward at the top of the sea ice. It is also concluded that the upward growth is caused by snow ice and superimposed ice formation. Superimposed ice formation on sea ice in Antarctica has not been reported previously. Evidence for snow cover melting, which is a prerequisite for superimposed ice formation, was also found. The summer upward growth was not found in sea ice with low snow accumulation. Snow cover, therefore, significantly affects the growth processes and structure of sea ice. General sea ice structure and characteristics of Antarctic sea ice are reviewed at the beginning of this report.