The biophysical role of water and ice within permafrost nearing collapse: Insights from novel geophysical observations

JGR Earth Surface
By: , and 



The impact of permafrost thaw on hydrologic, thermal, and biotic processes remains uncertain, in part due to limitations in subsurface measurement capabilities. To better understand subsurface processes in thermokarst environments, we collocated geophysical and biogeochemical instruments along a thaw gradient between forested permafrost and collapse-scar bogs at the Alaska Peatland Experiment (APEX) site near Fairbanks, Alaska. Ambient seismic noise monitoring provided continuous high-temporal resolution measurements of water and ice saturation changes. Maps of seismic velocity change identified areas of large summertime velocity reductions nearest the youngest bog, indicating potential thaw and expansion at the bog margin. These results corresponded well with complementary borehole nuclear magnetic resonance measurements of unfrozen water content with depth, which showed permafrost soils nearest the bog edges contained the largest amount of unfrozen water along the study transect, up to 25% by volume. In situ measurements of methane within permafrost soils revealed high concentrations at these bog-edge locations, up to 30% soil gas. Supra-permafrost talik zones were observed at the bog margins, indicating talik formation and perennial liquid water may drive lateral bog expansion and enhanced permafrost carbon losses preceding thaw. Comparison of seismic monitoring with wintertime surface carbon dioxide fluxes revealed differential responses depending on time and proximity to the bogs, capturing the controlling influence of subsurface water and ice on microbial activity and surficial emissions. This study demonstrates a multidisciplinary approach for gaining new understanding of how subsurface physical properties influence greenhouse gas production, emissions, and thermokarst development.

Study Area

Publication type Article
Publication Subtype Journal Article
Title The biophysical role of water and ice within permafrost nearing collapse: Insights from novel geophysical observations
Series title JGR Earth Surface
DOI 10.1029/2021JF006104
Volume 126
Issue 6
Year Published 2021
Language English
Publisher American Geophysical Union
Contributing office(s) Geology, Geophysics, and Geochemistry Science Center
Description e2021JF006104, 21 p.
Country United States
State Alaska
City Fairbanks
Other Geospatial Alaska Peatland Experiment (APEX) site
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