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Remote Sens. 2018, 10(8), 1312; https://doi.org/10.3390/rs10081312

Regional Patterns and Asynchronous Onset of Ice-Wedge Degradation since the Mid-20th Century in Arctic Alaska

1
ABR, Inc.—Environmental Research & Services, P.O. Box 80410, Fairbanks, AK 99708, USA
2
ABR, Inc.—Environmental Research & Services, P.O. Box 240268, Anchorage, AK 99518, USA
3
Alaska Ecoscience, 2332 Cordes Way, Fairbanks, AK 99709, USA
4
Water and Environmental Research Center, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
5
Alaska Geobotany Center, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
*
Author to whom correspondence should be addressed.
Received: 3 June 2018 / Revised: 15 August 2018 / Accepted: 17 August 2018 / Published: 20 August 2018
(This article belongs to the Special Issue Remote Sensing of Dynamic Permafrost Regions)
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Abstract

Ice-wedge polygons are widespread and conspicuous surficial expressions of ground-ice in permafrost landscapes. Thawing of ice wedges triggers differential ground subsidence, local ponding, and persistent changes to vegetation and hydrologic connectivity across the landscape. Here we characterize spatio-temporal patterns of ice-wedge degradation since circa 1950 across environmental gradients on Alaska’s North Slope. We used a spectral thresholding approach validated by field observations to map flooded thaw pits in high-resolution images from circa 1950, 1982, and 2012 for 11 study areas (1577–4460 ha). The total area of flooded pits increased since 1950 at 8 of 11 study areas (median change +3.6 ha; 130.3%). There were strong regional differences in the timing and extent of degradation; flooded pits were already extensive by 1950 on the Chukchi coastal plain (alluvial-marine deposits) and subsequent changes there indicate pit stabilization. Degradation began more recently on the central Beaufort coastal plain (eolian sand) and Arctic foothills (yedoma). Our results indicate that ice-wedge degradation in northern Alaska cannot be explained by late-20th century warmth alone. Likely mechanisms for asynchronous onset include landscape-scale differences in surficial materials and ground-ice content, regional climate gradients from west (maritime) to east (continental), and regional differences in the timing and magnitude of extreme warm summers after the Little Ice Age. View Full-Text
Keywords: permafrost; ice wedge; patterned ground; thermokarst; geomorphology; Arctic tundra; climate change; North Slope; Alaska permafrost; ice wedge; patterned ground; thermokarst; geomorphology; Arctic tundra; climate change; North Slope; Alaska
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Frost, G.V.; Christopherson, T.; Jorgenson, M.T.; Liljedahl, A.K.; Macander, M.J.; Walker, D.A.; Wells, A.F. Regional Patterns and Asynchronous Onset of Ice-Wedge Degradation since the Mid-20th Century in Arctic Alaska. Remote Sens. 2018, 10, 1312.

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