Geophysical Observations of Drained Permafrost Lake Taliks, North Slope, Alaska
Abstract
Lakes and drained lake basins in total cover approximately 80% of arctic lowland regions. Lake drainage, subsequent ecosystem succession in drained lake basins, and refreeze of the remnant talik has implications for carbon storage, landscape evolution, and hydrology. In some cases, taliks are thought to refreeze over the course of decades associated with top down and bottom up permafrost aggradation. However given the wide variety of drained lake basin sizes, locations, and ages, and the paucity of direct measurements, we are motivated to gain a more complete understanding of where taliks exist below drained lake basins. In order to answer the more general question of how quickly taliks refreeze after lake drainage, we first seek to understand the unique geophysical response of taliks measured using either transient electromagnetic (TEM) or surface nuclear magnetic resonance (NMR) methods. We surveyed a total of nine drained lake basins on the North Slope of Alaska ranging from near the coast of the Beaufort Sea to the silt (Yedoma) foothills of Oumalik. Relative time of drainage of each lake was estimated either by ecological or geomorphological characteristics or by radiocarbon dating of basal peat. Surface nuclear magnetic resonance soundings were most valuable due to the unambiguous ability to detect liquid water, however the bulky nature of the instrumentation prevented measurement at all sites. Transient electromagnetic soundings are interpreted either in conjunction with nearby surface NMR soundings, or through comparison with TEM soundings on nearby permafrost primary surfaces presumed to have not experienced lake formation and drainage. Through these measurements, clear evidence of a remnant talik in drained lake basins was observed at depth at several sites, while at other sites permafrost had aggraded and the material appeared to be refrozen. Due to the resistive properties and very low liquid water content of permafrost in our study region, refrozen taliks are interpreted based on the absence of TEM or surface NMR signal.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMNS11B0626P
- Keywords:
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- 0702 Permafrost;
- CRYOSPHERE;
- 0738 Ice;
- CRYOSPHERE;
- 0758 Remote sensing;
- CRYOSPHERE;
- 0794 Instruments and techniques;
- CRYOSPHERE