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Dissolved gases in perennially ice-covered lakes of the McMurdo Dry Valleys, AntarcticaMeasurements of dissolved N2, O2, Ar, CO2, and CH4 were made in perennially ice-covered Lake Hoare. Results confirm previous reports that O2 concentrations in the upper water column exceed atmospheric equilibrium and that N2 and Ar are supersaturated throughout the water column. The mean supersaturation of N2 was found to be 2.0 (+/- 0.37) and Ar was 3.8 (+/- 1.1). The ratios of N2/Ar (20.3 +/- 13.8), and O2/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 N2 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. CO2 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 micrograms l-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 O2, N2, and Ar at levels similar to levels found in Lake Hoare.
Document ID
20040089252
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
Authors
Andersen, D. T.
(NASA Ames Research Center Moffett Field CA United States)
McKay, C. P.
Wharton, R. A. Jr
Wharton RA, J. r.
Date Acquired
August 21, 2013
Publication Date
June 1, 1998
Publication Information
Publication: Antarctic science / Blackwell Scientific Publications
Volume: 10
Issue: 2
ISSN: 0954-1020
Subject Category
Exobiology
Funding Number(s)
CONTRACT_GRANT: NAGW-1947
CONTRACT_GRANT: OPP9-211773
CONTRACT_GRANT: NCA2-799
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Exobiology
Non-NASA Center

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