Permafrost Degradation Leaves Us on Thin Ice

The Tanana River flows through interior Alaska, a region characterized by discontinuous permafrost. Studies link degrading permafrost to increased winter river discharge due to increasing groundwater input. In winter, interior Alaskan rivers are exclusively fed by groundwater, which serves as an external source of heat. In fact, some portions of rivers fed by groundwater maintain thin ice throughout the winter, or remain altogether ice-free, despite very cold air temperatures. These ice conditions represent a significant danger to winter travellers who use rivers for wintertime travel, particularly in this largely roadless area.
We developed a physically-based, numeric model to explore how fluctuations in groundwater discharge control ice thickness on the Tanana River. The model allows us to examine how changes in groundwater flow affect ice dynamics by addressing two questions: 1) What are the dominant factors controlling seasonal ice dynamics on the Tanana River? 2) What are the rates of change in ice thickness resulting from observed and projected changes in these factors?