A Geochemical Study of Lakes Bonney and Vanda, Victoria Land, Antarctica

During Deep Freeze 61, highly saline water was found on the bottom of Lakes Vanda and Bonney, Victoria Land, Antarctica. These lakes, perennially ice-covered, have unusually warm waters for such cold environments. In December, 1960, the bottom 20-foot layer of Lake Vanda (217 feet± 5 feet deep) had a temperature of 22∘ ± 2∘ C. and Lake Bonney (100 feet ± 5 feet deep) had an 8° C. thermal layer at the 40-foot level. As the average annual temperature in this region is approximately -17° C, the only reasonable explanation for the high temperature observed in these waters appears to be either an unusually high geothermal gradient or the influx of warm spring waters on the lake bottoms. Analyses of water samples show abnormally high salinities, chlorinities, and conductivities. Interpretation of these data indicates that the lakes are meromictic. Investigation of the distribution of K⁺, Na⁺, Ca⁺⁺, Mg⁺⁺, SO₄⁺ and other ions provides some information as to probable origin of these waters. A SO₄/Cl ratio of 0.010 for the highly saline bottom waters of Lake Vanda indicates a possible sea-water origin. Determination of Mg⁺⁺/Ca⁺⁺ ratios indicates a probable salt water origin for the deeper waters (Mg/Ca = 23.6) of Bonney (elevation 38 m.) but not for Vanda (elevation 123 m.). The origin of these waters is not clear; however, present data suggest either a sea or thermal water origin for the monimolimnion of Lake Bonney. Whatever the origin of these saline bottom waters, many geologic and climatological implications are suggested.