Permanent Ice Covers of the Mcmurdo Dry Valley Lakes, Antarctica: Bubble Formation and Metamorphism

  1. John C. Priscu
  1. Edward E. Adams1,
  2. John C. Priscu2,
  3. Christian H. Fritsen2,
  4. Scott R. Smith3 and
  5. Steven L. Brackman3

Published Online: 16 MAR 2013

DOI: 10.1029/AR072p0281

Ecosystem Dynamics in a Polar Desert: the Mcmurdo Dry Valleys, Antarctica

Ecosystem Dynamics in a Polar Desert: the Mcmurdo Dry Valleys, Antarctica

How to Cite

Adams, E. E., Priscu, J. C., Fritsen, C. H., Smith, S. R. and Brackman, S. L. (1998) Permanent Ice Covers of the Mcmurdo Dry Valley Lakes, Antarctica: Bubble Formation and Metamorphism, in Ecosystem Dynamics in a Polar Desert: the Mcmurdo Dry Valleys, Antarctica (ed J. C. Priscu), American Geophysical Union, Washington, D. C.. doi: 10.1029/AR072p0281

Author Information

  1. 1

    Civil Engineering Department, Montana State University, Bozeman, Montana

  2. 2

    Department of Biological Sciences, Montana State University, Bozeman, Montana

  3. 3

    Civil Engineering Department, Montana State University, Bozeman, Montana

Publication History

  1. Published Online: 16 MAR 2013
  2. Published Print: 28 JAN 1998

ISBN Information

Print ISBN: 9780875908991

Online ISBN: 9781118668313

SEARCH

Keywords:

  • Desert ecology—Antarctica—McMurdo Dry Valleys

Summary

The permanent ice covers of liquid water based lakes in the McMurdo Dry Valleys are thermodynamically active and display a well defined but transitory stratigraphy. We discuss the annual development of the physical structure of the ice based on field measurements, data gathered during the austral winter and spring of 1994 and 1995, laboratory experiments, and quantitative analysis. In general, the ice growth takes place on the bottom of the ice cover with ablation from the top. Sediment deposited on the ice surface by aeolian processes migrates downward through the ice. The migration is driven by a combination of solar absorption and seasonal warming, leaving a liquid melt trail in its path. The sediment collects in discrete pockets forming a layer with clean ice above and below. Attenuation of solar energy coupled with the brief duration of the relatively warmer portion of the summer season limit the sediment's level of descent. During the austral summer an aquifer is created in the ice, with its lower boundary marked by the sediment layer. The aquifer is connected to the lake water through conduits and the lower ice remains essentially dry. A complex ice stratigraphy is produced as the result of top down freezing of the liquid water in the ice during fall and winter. Inverted teardrop shaped bubbles with diameter generally under 5mm are produced in the upper meter of the ice. Arching plume-like bubbles and umbrella shaped waves of small spherical bubbles develop as the liquid freezes in the vicinity immediately above the sediment pockets. These patterns are governed by the shape of the freezing front. Liquid filled cavities in the ice induce local curvature of the freezing front, the shape of which is determined by differences in thermal conductivity of the water phases. Hoar frost, produced by temperature gradients, is apparent on the upper surfaces of many bubbles. Just below the sediment, a cluster of circular horizontal fractures develop when expansion due to the phase change of liquid entrapped in cylindrical bubbles causes failure. Fracture occurs on the basal plane of the S 1 (c-axis vertical) ice. The lower region of the ice cover is characterized by vertically oriented cylindrical gas bubbles that develop when water freezes to the bottom of the ice cover. The bubbles, fractures, and sediment configuration influence light transmission/absorption, heat flux, and mass transport, all of which are important to the biogeochemical processes in the lake.