PHYSICOCHEMICAL LIMNOLOGY OF LAKE BONNEY, ANTARCTICA

Abstract

Lake Bonney is a permanently ice‐covered lake of 3.2 km² in upper Taylor Valley, Victoria Land, Antarctica. The mean depth, without ice cover, is 18.7 m. The lake probably occupies a glacially overdeepened valley. The lake is meromictic. The maximal temperature of 7C coincides with the chemocline at about 15 m; the temperature decreases to a range of +2 to ‒4C in the bottom waters and to less than 1C beneath the ice. Calculations of superficial water inflow and of water loss by sublimation of ice indicate that the lake is slowly shrinking. Old shorelines above the present lake level attest to shrinkage. Part of the difference between water gain and water loss is made up by inflow of warm‐spring water at depth. Such springs are probably the major source of heat for the lake. Total solids in the monimolimnion range up to 407.3 g/liter. Sodium and magnesium chloride account for 96% of the dissolved salts. An analysis of ionic ratios suggests that the lake waters may consist of trapped seawater highly modified by subsequent concentration by evaporative processes, by addition of ions from surrounding soils, and by addition of warm‐spring water. The ionic concentrations are altered in part by the precipitation of CaSO₄, CaCO₃, and Na₂SO₄.