Dissolved gases in perennially ice-covered lakes of the McMurdo Dry Valleys, Antarctica

• Published in: Antarctic Science
• Main Authors: Andersen, D.T., Mckay, C.P., Wharton, R.A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1998
• Subjects: Geology; Ecology, Evolution, Behavior and Systematics; Oceanography; McMurdo Dry Valleys; Miers; Vanda; Hoare; Lake Hoare; Antarc*; Antarctic Science; Antarctica
• Online Access: http://dx.doi.org/10.1017/s0954102098000170; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0954102098000170

Measurements of dissolved N 2 , O 2 , Ar, C O2 , and CH 4 were made in perennially ice-covered Lake Hoare. Results confirm previous reports that O 2 concentrations in the upper water column exceed atmospheric equilibrium and that N 2 and Ar are supersaturated throughout the water column. The mean supersaturation of N 2 was found to be 2.0 (±0.37) and Ar was 3.8 (±1.1). The ratios of N 2 /Ar (20.3 ±3.8), and O 2 /Ar (22.5 ±4.0) at the ice-water interface are consistent with those previously measured, suggesting that bubble formation is the main process for removing gas from the lake. However, the saturations of N 2 and Ar greatly exceed those previously predicted for degassing by bubble formation only at the ice-water interface. The data support the hypothesis that removal of gas by bubbles occurs in the water column to a depth of 11 m in Lake Hoare. CO 2 concentration increases from near zero at the ice-water interface to 80–100 times saturation at and below the chemocline at c . 28 m. There is considerable variability in the gas concentrations throughout the water column; samples separated in depth by one metre may vary by more than 50% in gas content. It is likely that this phenomenon results from the lack of turbulent mixing in the water column. Methane ( c . 2 μg 1 −1 ) was detected below the chemocline and immediately above the sediment/water interface at a depth of 30 m. Samples from lakes Vanda, Joyce, and Miers, also show supersaturations of O 2 , N 2 , and Ar at levels similar to levels found in Lake Hoare.