This paper will present preliminary results of an investigation of ice growth on shallow, thaw lakes and its role in affecting the thermal regime of the soils below and adjacent to the lakes, and the potential impacts of climate change on the coupled ice/water/soil system.
There are thousands of shallow, thaw lakes on the North Slope of Alaska where they comprise over 20% of the total area and perhaps as much as 40% of the area of the Coastal Plain under present climate conditions. All or part of most lakes are <2m deep, i.e., equivalent to the maximum, end of winter ice thickness; consequently, a significant area of ice grounds and freezes completely to the bottom each winter. Also, there are only a few weeks each year when the lakes are completely ice free. The lake depth and ice growth determine (1) the distribution and area of grounded ice in a given region, and (2) the volume of the thaw zone beneath and adjacent to the lake basins.
Spaceborne synthetic aperture radar (SAR) images from the Alaska SAR Facility are used to identify when and how many lakes in the Kuparuk River basin froze completely to the bottom in winter 1995 96. Ice growth on the lakes is simulated with a one dimensional numerical model in order to determine the ice thickness at the time each lake froze completely to the bottom. This maximum ice thickness corresponds to the maximum water depth of any lake that freezes completely. When applied to a winter long series of SAR images, this method can be used to determine the bathymetry of individual lakes, and to determine the water depth distribution and water availability in a population of lakes.
The lake ice growth model is coupled to a two-dimensional permafrost model to simulate the effects of ice growth and the complete freezing of lakes on the soil thermal regime below and adjacent to the lakes. The soil thermal regimes associated with different lake basin shapes and sizes are simulated, and sensitivity tests are run in order to assess some of the potential impacts of climate change, e.g., warmer winters and/or thicker snow cover reducing the maximum ice thickness and resulting in a decrease in the area of ice that freezes completely to the bottom of lakes and thus greater winter availability.
Martin O. Jeffries Geophysical Institute University of Alaska Fairbanks 903 Koyukuk Dr. P.O. Box 757320 Fairbanks, AK 99775-7320 Telephone: 907-474-5257 Fax: 907-474-7290 E-mail: martin.jeffries@gi.alaska.edu Tingjun Zhang Geophysical Institute University of Alaska Fairbanks P.O. Box 757320 Fairbanks, AK 99775-7320 Wei Zhou Geophysical Institute University of Alaska Fairbanks P.O. Box, 757320 Fairbanks, AK 99775-7320 Jamie Pflasterer Dept. of Civil Engineering and Environmental Science University of Oklahoma Norman, OK 73072 Glen E. Liston Dept. of Atmospheric Science Colorado State University Fort Collins, CO 80523-1371