Effects of Hillslope Thermokarst in Northern Alaska

Permafrost thawing is increasing in the Arctic and sub‐Arctic [ Osterkamp and Romanovsky , 1996; Osterkamp , 2007] in response to climate warming [ Hassol , 2004]. One consequence of thawing permafrost is the development of thermokarst (physical depression of ground surface) because of reduced support of overlying soil [ Jorgenson et al. , 2006]. Thermokarst lakes, for example, result from changes to surface energy balance, which drive permafrost thaw locally, such that a topographic depression develops and captures water, forming a lake or pond. Climate warming of the past several decades is expected to increase the occurrence of thermokarst. For example, Agafonov et al. [2004] have noted that the rate of expansion of a single thermokarst depression in western Siberia has increased in the latter half of the twentieth century, coincident with increasing air temperature and precipitation during the thaw season.