Morphology and dynamics of thermokarst ponds in a subarctic permafrost peatland, northern Sweden

Abstract

Rapid climatic changes cause permafrost to thaw, initiating thermokarst landforms such as lakes and ponds. These waterbodies cover large extents of the northern circumpolar permafrost region and are significant sources of greenhouse gases. For the assessment of current and potential future waterbody development, continuous monitoring and analyses of the driving factors are required. In Dávvavuopmi, a permafrost peatland located in the sporadic permafrost zone of northern Sweden, high-resolution imagery of the first two decades of the 21st century is available. This study combined field, GIS and statistical methods to explain spatiotemporal pond dynamics by investigating pond morphology and regional climate characteristics. Erosion affected 42% of the shorelines, and the erosion intensity was significantly correlated with the height and slope of bluffs facing the waterbodies. Along some sections, active erosion was causing shoreline retreat, but the dominant trend in this landscape was pond drainage and terrestrialisation/fen vegetation ingrowth. Between 2003 and 2021 the thermokarst pond area and number decreased by 6%/decade and 27%/decade, respectively. Inter- and intra-annual climatic parameters could not be directly linked to thermokarst pond dynamics. Instead, the climate conditions (MAAT/snow depth) control permafrost degradation, causing enhanced hydrological connectivity in the landscape, which drives the pond drainage trend.