Geophysical imaging reveals brine system beneath an ice-sealed Antarctic lake

Friday, 19 December 2014
Hilary Dugan, University of Illinois at Chicago, Chicago, IL, United States, Peter T Doran, Univ Illinois at Chicago, Chicago, IL, United States, Slawek M Tulaczyk, Univ California Santa Cruz, Santa Cruz, CA, United States, Jill Mikucki, University of Tennessee, Knoxville, TN, United States, Steven A Arcone, U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, NH, United States, Esben Auken, Aarhus University, Aarhus, Denmark, Cyril Schamper, Sorbonne Universit├ęs, Paris, France and Ross A Virginia, Dartmouth College, Hanover, NH, United States
The habitability of polar desert environments on Earth, and other neighboring planets, is dependent on the availability of liquid water. In areas where the surface is frozen, lenses of water present in the subsurface may act as microbial refugia. In the McMurdo Dry Valleys of Antarctica, the presence of highly saline brine in valley lakes raises the potential for the existence of a deep groundwater network. We report on a geophysical study that shows Lake Vida, in Victoria Valley, is nearly frozen, and the remaining brine is confined beneath thick ice. Near surface, bathymetric mapping of grounded lake ice was accomplished from a series of ground penetrating radar surveys. Radar penetration was limited to 20 m. An airborne transient electromagnetic survey (AEM) revealed a low resistivity zone at 30-100 m depth beneath the surface of the lake. Based on previous knowledge of brine chemistry and local geology, this zone is interpreted as brine saturated unconsolidated sediments with a porosity of 23-42%. Brine volume is calculated at 15 to 32 million cubic meters, which is of similar magnitude to the brine volume in nearby saline lakes. The AEM survey provided a means of quantifying the spatial extent of deep subsurface brine in this remote environment, and has provided a new perspective on the potential for subsurface habitats in areas often considered devoid of life.