Preprints
https://doi.org/10.5194/tc-2020-241
https://doi.org/10.5194/tc-2020-241

  25 Sep 2020

25 Sep 2020

Review status: this preprint is currently under review for the journal TC.

Thermal legacy of a large paleolake in Taylor Valley, East Antarctica as evidenced by an airborne electromagnetic survey

Krista F. Myers1, Peter T. Doran1, Slawek M. Tulaczyk2, Neil T. Foley2, Thue S. Bording3, Esben Auken3, Hilary A. Dugan4, Jill A. Mikucki5, Nikolaj Foged3, Denys Grombacher3, and Ross A. Virginia6 Krista F. Myers et al.
  • 1Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803, USA
  • 2Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA
  • 3Department of Geoscience, Aarhus University, Aarhus, Denmark
  • 4Center for Limnology, University of Wisconsin-Madison, Madison, WI 53706, USA
  • 5Department of Microbiology, University of Tennessee, Knoxville, Knoxville, TN 37996, USA
  • 6Environmental Studies, Dartmouth College, Hanover, NH 03755, USA

Abstract. Previous studies of the lakes of the McMurdo Dry Valleys have attempted to constrain lake level history, and results suggest the lakes have undergone hundreds of meters of lake level change within the last 20,000 years. Past studies have utilized the interpretation of geologic deposits, lake chemistry, and ice sheet history to deduce lake level history, however a substantial amount of disagreement remains between the findings, indicating a need for further investigation using new techniques. This study utilizes a regional airborne resistivity survey to provide novel insight into the paleohydrology of the region. Mean resistivity maps revealed an extensive brine beneath the Lake Fryxell basin which is interpreted as a legacy groundwater signal from higher lake levels in the past. Resistivity data suggests that active permafrost formation has been ongoing since the onset of lake drainage, and that as recently as 1,000–1,500 yr BP, lake levels were over 60 m higher than present. This coincides with a warmer than modern paleoclimate throughout the Holocene inferred by the nearby Taylor Dome ice core record. Our results indicate mid to late Holocene lake level high stands which runs counter to previous research finding a colder and drier era with little hydrologic activity throughout the last 5,000 years.

Krista F. Myers et al.

 
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Krista F. Myers et al.

Krista F. Myers et al.

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Short summary
Lake Fryxell, Antarctica, has undergone hundreds of meters of change in recent geologic history. However, there is disagreement on when lake levels were higher, and by how much. This study uses resistivity data to map the subsurface conditions (frozen versus unfrozen ground) to map ancient shorelines. Our models indicate that Lake Fryxell was up to 60 m higher just 1,000 to 1,500 years ago. This amount of lake level change shows how sensitive these systems are to small changes in temperature.