Thermokarst lakes expand and drain laterally as permafrost degrades



In Arctic regions, thermokarst lakes form and expand from thawing permafrost or melting of ice. However, as lakes expand they have a tendency to drain laterally. Jones et al. surveyed the extent of thermokarst lakes in the continuous permafrost zone in the Cape Espenberg lowland of northwestern Alaska's Seward Peninsula using high-resolution remote sensing imagery during 1950–1951, 1978, and 2006–2007. They found that most thermokarst lakes have been expanding at an average rate of 0.3 meter per year as permafrost degrades, with rates relatively stable over the 56-year observation period. When viewed from above, a ring of expansion along most lake margins was visible; however, several ver y large lakes drained laterally during this observation period as the expanding lakes encountered a topographic drainage gradient. The authors report that this pattern of particularly large lakes being more prone to drainage resulted in more land area gain than land area loss since 1950 and may represent a carbon sink as these drained basins begin to accumulate peat.