Investigation of the gas budget of subglacial lake vostok
Abstract
Buried beneath ~4 km thick East Antarctic ice sheet Lake Vostok has the potential to be the most unique habitat for life on the Earth. Knowledge of gas concentrations within the lake is of particular importance with respect to its ability to support or suppress life under the ice. Owing to the high pressures and low temperatures, the gas dynamics in subglacial lakes is complicated by possible formation of a mixed gas clathrate-hydrate which should occur here in the event of gas supersaturation. Preliminary analyses of the small amount of gas extracted from the deepest section of the Vostok ice core show that nitrogen and oxygen are the major gas constituents in the accretion (lake) ice. This indicates that the gas composition and the total gas content of sub-ice water are mostly controlled by the ice-water exchange between the lake and the overlying ice sheet, which process leads to accumulation of N2 and O2 within the lake. Based on the data from air content measurements and modern estimates of the lake water renewal time, we quantified the contribution from ice melting-refreezing to the bulk gas budget of Lake Vostok. We determined the conditions of air hydrate stability in the lake water and calculated the solubility of N2 and O2 in equilibrium with a hydrate phase. As the next step, we applied the multi-component gas hydrate modeling to show how the presence of small quantities of methane and carbon dioxide, if they were released into the water column from the lake floor, could affect the equilibrium between hydrate and dissolved gases. In all plausible scenarios, the calculated concentrations of dissolved O2 fall between 0.027 and 1.3 g/l whereas the upper bound is reached when dissolved gases are in equilibrium with air hydrate. Our study show that the hydrate growth in Lake Vostok is a distinct possibility and therefore the concentration of dissolved O2 in Lake Vostok is significantly (up to 50 times) higher than that in the air-supersaturated perennially ice-covered surface lakes in Antarctica. The biological implications of the high oxygen tension in Lake Vostok will be discussed in accompanying presentation.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....5752L