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This dataset provides field observations of thaw depth and dominant vegetation types, a LiDAR-derived elevation map, and permafrost distribution and probability maps for an area on the coastal plain of the Yukon-Kuskokwim Delta (YKD), in western Alaska, USA. Field data were collected during July 8-17, 2016 to parameterize and to validate the derived permafrost maps. The YKD is in the sporadic to isolated permafrost zone where permafrost forms extensive elevated plateaus on abandoned floodplains. The region is extremely flat and vulnerable to eustatic sea-level rise and inland storm surges. These high-resolution permafrost maps support landscape change analyses and assessments of the impacts of climate change on permafrost in this region of high biological productivity, critical wildlife habitats, and subsistence-based human economy.

for a copy of this paper please contact the Yukon Geological Survey; geology@gov.yk.ca.

Geophysical measurements and related field data were collected by the U.S. Geological Survey (USGS) at the Alaska Peatland Experiment (APEX) site in Interior Alaska from 2018 to 2020 to characterize subsurface thermal and hydrologic conditions along a permafrost thaw gradient. The APEX site is managed by the Bonanza Creek LTER (Long Term Ecological Research). In April 2018, seven boreholes were emplaced to depths of 2.3-2.5 meters (m) to allow for repeat logging with downhole nuclear magnetic resonance (NMR) to quantify the spatial and temporal variations in unfrozen water content within active-layer and permafrost soils. NMR data were collected on ten separate occasions between April 2018 and October 2020. In June 2018, soil temperature and moisture sensors were installed at select locations and depths across the study site to record point-scale temperature and moisture conditions in 30 minute intervals. In August 2018, electrical resistivity tomography (ERT) data were collected along four 82 m-long transects. Models of electrical resistivity produced from these data revealed the spatial variability in soil lithology and thermal state (frozen vs. thawed) to depths up to 10-15 m below the surface. Lastly, manual permafrost-probe measurements of thaw depths were collected at each instrument location during summer site visits for comparison to the geophysical data.

Geophysical measurements and related field data were collected by the U.S. Geological Survey (USGS) at the Alaska Peatland Experiment (APEX) site in Interior Alaska from 2018 to 2020 to characterize subsurface thermal and hydrologic conditions along a permafrost thaw gradient. The APEX site is managed by the Bonanza Creek LTER (Long Term Ecological Research). In April 2018, seven boreholes were emplaced to depths of 2.3-2.5 meters (m) to allow for repeat logging with downhole nuclear magnetic resonance (NMR) to quantify the spatial and temporal variations in unfrozen water content within active-layer and permafrost soils. NMR data were collected on ten separate occasions between April 2018 and October 2020. In June 2018, soil temperature and moisture sensors were installed at select locations and depths across the study site to record point-scale temperature and moisture conditions in 30 minute intervals. In August 2018, electrical resistivity tomography (ERT) data were collected along four 82 m-long transects. Models of electrical resistivity produced from these data revealed the spatial variability in soil lithology and thermal state (frozen vs. thawed) to depths up to 10-15 m below the surface. Lastly, manual permafrost-probe measurements of thaw depths were collected at each instrument location during summer site visits for comparison to the geophysical data.

The distribution of permafrost in cold regions is subject to temporal and spatial changes influenced by climate, landscape disturbance, and ecosystem succession. Remote sensing from airborne and satellite platforms is increasing our understanding of landscape-scale permafrost distribution, but typically lacks the resolution to characterize finer-scale processes and phenomena, which are often better captured by surface geophysical methods. Specifically, the electrical conductivity of the earth can be used to infer lithological and pore fluid properties, and in this case to delineate frozen, partially frozen, and unfrozen ground. Here, we present electromagnetic induction (EMI) data collected in August 2012 around the highly dynamic Twelvemile Lake, Yukon Flats, central Alaska, USA. This data release presents raw and processed results from hand-carried frequency domain EMI data collected with the GEM-2 instrument (Geophex, Ltd.) at approximately 0.75 m off the ground in both vertical and horizontal coplanar modes.