Mapping and Monitoring of Sweden’s largest coherent palsa mire

Palsas are a permafrost landform found in northern peatlands, characterized by peat mounds with a frozen core. Climatic changes cause widespread degradation of palsas, affecting biodiversity, hydrology, carbon fluxes, and local infrastructure. Therefore, palsa mires are considered a priority habitat under the EU Species and Habitat Directive and are integrated into Sweden’s environmental goals, such as maintaining Thriving Wetlands. Despite their threatened status, the largest coherent palsa mire in Sweden, Vissatvuopmi (N68°47’, E21°11′), has no protective status. At this site, we monitor several palsas and peat plateaus, using a wide range of methods to understand both exterior and interior dynamics. We use a UAV with a LiDAR scanner to obtain high-resolution terrain models and track topographical changes. Between September 2022 and September 2024, we observed several “degradation hotspots” that undergo rapid collapse. Annual LiDAR data are supported by UAV orthophotos and the monitoring of active layer thickness, ground temperatures in six boreholes (2–6 m deep), and the local climate. Regarding the palsas’ interior, we present a comprehensive pseudo-3D survey of Electrical Resistivity Tomography (ERT). The results indicate that the shape of the frozen core on a palsa is highly heterogeneous, with a maximum depth roughly three times the height of the palsa. Finally, cores down to 5 m reveal a thick (up to 2 m) peat layer and thick ice lenses at depth. This multi-method approach provides a comprehensive view of palsas’ structure and will help advance our understanding of how peatland permafrost responds to a rapidly changing climate.