Expansion rate and geometry of floating vegetation mats on the margins of thermokarst lakes, northern Seward Peninsula, Alaska, USA

ABSTRACT Investigations on the northern Seward Peninsula in Alaska identified zones of recent (<50 years) permafrost collapse that led to the formation of floating vegetation mats along thermokarst lake margins. The occurrence of floating vegetation mat features indicates rapid degradation of nea...

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Bibliographic Details
Published in:Earth Surface Processes and Landforms
Main Authors: Parsekian, Andrew D., Jones, Benjamin M., Jones, Miriam, Grosse, Guido, Walter Anthony, Katey M., Slater, Lee
Format: Article in Journal/Newspaper
Language:English
Published: Wiley 2011
Subjects:
Earth and Planetary Sciences (miscellaneous)
Earth-Surface Processes
Geography, Planning and Development
permafrost
Seward Peninsula
Thermokarst
Alaska
Online Access:http://dx.doi.org/10.1002/esp.2210
https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fesp.2210
https://onlinelibrary.wiley.com/doi/pdf/10.1002/esp.2210
https://onlinelibrary.wiley.com/doi/full-xml/10.1002/esp.2210
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Summary:ABSTRACT Investigations on the northern Seward Peninsula in Alaska identified zones of recent (<50 years) permafrost collapse that led to the formation of floating vegetation mats along thermokarst lake margins. The occurrence of floating vegetation mat features indicates rapid degradation of near‐surface permafrost and lake expansion. This paper reports on the recent expansion of these collapse features and their geometry is determined using geophysical and remote sensing measurements. The vegetation mats were observed to have an average thickness of 0.57 m and petrophysical modeling indicated that gas content of 1.5–5% enabled floatation above the lake surface. Furthermore, geophysical investigation provides evidence that the mats form by thaw and subsidence of the underlying permafrost rather than terrestrialization. The temperature of the water below a vegetation mat was observed to remain above freezing late in the winter. Analysis of satellite and aerial imagery indicates that these features have expanded at maximum rates of 1–2 m yr ‐1 over a 56 year period. Including the spatial coverage of floating ‘thermokarst mats’ increases estimates of lake area by as much as 4% in some lakes. Copyright © 2011 John Wiley & Sons, Ltd.

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