Fine-scale observation on salinity stratification in an ice hole during melting season of Antarctic sea ice

Abstract

Observation on the seasonal variation of temperature and salinity of seawater was carried out through an ice hole at a station near Syowa Station as part of the 25th Japanese Antarctic Research Expedition. During the period from March 1984 to January 1985,temperature salinity stratification was observed only in summer in the upper layers of the seawater. In order to clarify the microstructure of the stratification, fine-scale observations on temperature and salinity profiles were conducted through the ice hole with the use of the CSTD monitor at the depth intervals from 5 to 10 cm on January 6,1985. The results revealed that an intensified halocline occurred at the depth between 120 and 150 cm, where salinity changed considerably from 3.33 to 27.88‰. This observed halocline is supposed to exist in the underlying seawater immediately below sea ice around the ice hole. Such a condition may naturally occur in the area of paddles with thawing holes and cracks. Ice algae inhabiting the undersurface of ice may be physiologically affected by the extremely low salinity of the underlying seawater.