Measurements of major ion concentrations, 1) 18 0 , and 14C

The average yearly net ablation rate on permanently ice-covered Lake Fryxell, Victoria Land, Antarctica, is 30 to 40 cm. This figure was calculated by a novel method utilizing a record of ablation which is incorporated in the ice cover of the lake. These values are higher than those measured on Ross Island 80 km. to the east; the difference in ablation rates for the two areas is attributed to the prevalence of katabatic winds in the climate of Taylor Valley. The Lake Fryxell ablation figure is applied to nearby Canada and Commonwealth Glaciers in the calculation of their ice budgets.

Introduction. Lake Fryxell (77°37′S, 163° 6′E) occupies the lowest part of an enclosed drainage basin near the seaward (eastern) end of the Taylor Valley, Victoria Land. The lake, 5 km by 1½ km, is permanently covered by about 4.5 meters of ice. Angino et al. [1962] first investigated the lake and showed that it contained chemically and thermally stratified water.

The chemical composition of south polar snow is of interest because of the remoteness of the snow from the earth's oceans, being at an altitude of 2700 m and a distance of 1600 km from the ocean in summer and twice that distance in winter. Unlike measurements made at the centers of other large continents, measurements made at the South Pole are not subject to contamination. It was found that the annual infall at the South Pole is 10−7 g/cm2 for Na+, 5×10−8 g/cm2 for K +, 2×10−7 g/cm2 for Cl−, and 5×10−8 g/cm2 for nitrogen as NO2− + NO3−. It is proposed that the Na+, K+, and Cl− come from the oceans and the NO2− + NO3− from auroral activity and other geophysical phenomena in the upper atmosphere. From these data it is concluded that salt spray particles from the sea reach even this remote part of the earth's surface and that the contribution of fixed nitrogen to the earth's biosphere by geophysical processes in the upper atmosphere is ≤0.005 kg/hectare/yr.

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