Seasonal variations in water structure under fast ice near Syowa Station, Antarctica, in 1976

Formation of homogeneous water was observed in the surface layer above a depth of 400m in the Ongul Strait in early September of 1976 when fast ice had the maximum thickness. This water was produced from stratified water as a result of haline convection induced by the exclusion of brine during the growth of fast ice from 1m in thickness in May to about 2m in early September. The salinity of surface water in this strait also increased from 33.93‰ to 34.10‰ by the convection process during the ice growth. Meanwhile in the Hovdebukta, water with the maximum salinity of 35.03‰ was observed at 300m. The formation of the saline water is probably due to the exclusion of brine by the rapid freezing of sea water in cracks as well as by the gradual growth of fast ice. With the beginning of the spring a marked decrease was seen in salinity of bottom water in the Ongul Strait and of intermediate and bottom waters in the Hovdebukta despite a rather increasing salinity of surface water in both areas. It can be explained only by the advection of less saline water into the deeper layers in both areas. The saline water produced by the exclusion of brine was expected to remain near the bottom of glacial troughs until summer, but it was not observed there in summer. An interpretation is given that the saline water disappeared as a result of the advection of less saline water off the Soya Coast and/or the inflow of fresh water produced in the coast of the continent, probably from the bottom of glaciers from spring onward