Changes in lake area in response to thermokarst processes and climate in Old Crow Flats, Yukon

Growing evidence indicates that lake-dominated ecosystems at high latitudes are undergoing significant hydrological changes. Research examining these changes is complicated because both thermokarst and climatic processes likely influence lake dynamics. To examine the relative impacts of these processes in permafrost landscapes, we investigated the dynamics of lake area and number in Old Crow Flats (OCF), Yukon using historical air photos and satellite imagery. Between 1951 and 2007, OCF experienced a decline of similar to 6000ha in total lake area but gained 232 lakes. Close to half (49%) of the difference in lake area was driven by the rapid and persistent drainage of 38 large lakes. These catastrophic drainages were associated with new or enlarged outlet channels, resulted in the formation of numerous residual ponds, and were likely driven by thermokarst processes. Our analysis shows that catastrophic lake drainages have become more than 5 times more frequent in recent decades. These changes are likely related to the impacts of increased temperature and precipitation on thermokarst processes. Fifty-nine of the 170 intensively studied lakes showed either large bidirectional fluctuations or gradual cumulative declines. These changes affected a much smaller portion of OCF and were likely driven by interactions between increased precipitation and temperature and individual catchment characteristics. To anticipate landscape-scale changes in these systems, and assess their impact on hydrology, wildlife habitat, and carbon storage, field research is required to better characterize the mechanisms responsible for changes. Key Points