Accumulation of Excess Ground Ice in an Age Sequence of Drained Thermokarst Lake Basins, Arctic Alaska

• Published in: Permafrost and Periglacial Processes
• Main Authors: Bockheim, J. G., Hinkel, K. M.
• Other Authors: National Science Foundation
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2012
• Subjects: Arctic; Barrow; Ice; permafrost; Permafrost and Periglacial Processes; Thermokarst; wedge*; Alaska
• Online Access: http://dx.doi.org/10.1002/ppp.1745; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fppp.1745; https://onlinelibrary.wiley.com/doi/pdf/10.1002/ppp.1745

ABSTRACT The excess ice content of near‐surface permafrost near Barrow, Alaska, was estimated using cores collected from 57 drained thermokarst‐lake basins and additional cores from a nearby landform unaffected by thaw‐lake processes. The excess ice content, estimated using soil cryostructures, increased with surface age: from 20 per cent in young basins < 50 years in age to 40 per cent in ancient basins that drained 2000–5500 years ago. The frequency of ice wedges encountered during coring increased from 0 per cent in young basins to 50 per cent in ancient basins. These results indicate that the volume of ground ice increases rapidly immediately following lake drainage, as permafrost aggrades into unfrozen basin sediments. Ice enrichment continues over time by incorporating meteoric water as ice veins and lenses, and expanding networks of ice wedges. To test the efficacy of visually estimating excess ice content, the ice content was measured on a subsample of cores; measured volumetric values were strongly correlated (r 2 = 0.72; p < 0.001) to the estimated excess ice content. The results of this study have important implications for estimating soil organic carbon content of soils with abundant excess ice, and for evaluating the susceptibility of these soils to thermokarst. Copyright © 2012 John Wiley & Sons, Ltd.