Lakes as geoindicators of thermokarst landscape changes following wildfires

Abstract

Rapid landscape changes in the Arctic are occurring at an accelerated rate. The most common disturbances that cover the largest areas of the Arctic are wildfires. It is well known that lakes serve as a good proxy for identifying thermokarst processes. However, the impact of fires is often overlooked in analyses of lake dynamics. This paper aims to validate if thermokarst lakes can be treated as geoindicators of permafrost degradation after wildfires. We analyzed changes in the spatial extent of the thermokarst lakes after wildfires at the part of the Mackenzie River watershed. For that purpose, we examined changes in thermokarst lakes in five test areas before the fire, short and long term after fires, and compared the results with similar unburned areas. Our findings indicate that lake responses to wildfires vary significantly, with no consistent area increase or decrease pattern. However, burned areas exhibit greater variability in lake size compared to unburned sites, suggesting that wildfire disturbances create a state of geoecological disharmony. Long-term reductions in the lakes area point to permanent permafrost degradation, while some lakes expanded, likely due to thermokarst processes. Our results emphasize the potential of thermokarst lakes as indicators of post-fire permafrost changes, reinforcing the need for further research to develop quantitative methods for assessing permafrost degradation in wildfire-affected regions.