permafrostsmelten

Permafrost melt, or thaw, refers to the progressive warming and degradation of permafrost soils that have remained frozen for at least two consecutive years. Permafrost underlies large areas of the Arctic and high mountain regions. As air and soil temperatures rise, the depth of the active layer—the seasonal zone of thaw above the permafrost—deepens, allowing frozen soils to thaw gradually and in pulses.

In ice-rich permafrost, thaw can be abrupt and produce thermokarst, landforms characterized by surface subsidence, slumps, and the formation of thaw lakes. Snow cover, soil moisture, and drainage influence thaw rates. Climate warming accelerates both gradual deepening of the active layer and episodic abrupt thaw events, potentially exposing previously insulated organic carbon to decomposition.

Consequences include release of greenhouse gases such as carbon dioxide and methane from previously frozen organic matter, contributing to atmospheric warming. Thaw undermines infrastructure and increases landslides, sediment transport, and waterlogging, jeopardizing buildings, roads, and pipelines. Ecological changes follow, with shifts in vegetation communities, hydrology, and habitat availability for Arctic species.

Monitoring combines ground measurements—borehole temperatures, active-layer thickness—and remote sensing approaches, including satellite radar and lidar, to map subsidence and lake formation. Models project continued thaw with regional differences, depending on climate, soil properties, and moisture.

Geographically, permafrost is most extensive in the Arctic and high mountains, including Siberia, Alaska, Canada, Greenland, and the northern Andes. Understanding permafrost melt is essential for climate projections and adaptation planning in northern infrastructure, communities, and ecosystems.