Long-term Variations in Ice Formation and Breakup Dates for a Thermokarst Lake in Barrow, Alaska: Climatic Drivers and Hydrologic Impacts

More than one fourth of the world's lakes are located in the Arctic, where climate change is known to be occurring at a rapid pace. Many of these lakes are located in regions of continuous or discontinuous permafrost, and the Arctic Coastal Plain (ACP) of northern Alaska has an especially high density of thermokarst lakes. Roughly 40% of the ACP landscape is comprised of lakes or drained lake basins, highlighting the need for long-term lake monitoring through programs such as the Arctic Observing Network (AON). In recognition of this, a collaborative project was begun in 2012 to establish a 'Circum-Arctic Lakes Observation Network (CALON),' which includes extensive monitoring of nearly 60 lakes on the ACP. CALON team members have also interacted with local residents in Arctic communities to identify additional sources of information on thermokarst lakes. One such community is Barrow, Alaska, where long-term observations of ice formation and breakup dates for an inland lake (Isatkoak Lagoon) have been made since 1987. The lake ice record shows a clear trend toward later freeze dates (~7.7 days per decade) and earlier breakup dates (~3.4 days per decade), with an overall decline in ice duration of about 28 days over the 25-year period (1987-2012). Similar delays in freeze-up dates since 1999 (~5 days per decade) have also been noted for a local fishing site (Ikroagvik Lake), based on the ability to access the lake in autumn to set and retrieve fishnets. Combined with local meteorological data, trends in snowmelt dates, and recent summertime energy balance data from the primary CALON study lake in Barrow, we investigate the various climatic drivers of the observed decline in lake ice duration, as well as the impact of the prolonged ice-free season on Arctic lake hydrology.