Subsurface Investigations of Cryo‐Hydrogeological Features in a High Arctic Catchment Under Transition

In this study, the internal structure and seasonal variations of cryo‐hydrogeological features were investigated in the Fuglebekken catchment, located near the Polish Polar Station Hornsund in Svalbard. Over a few years, rising air temperatures and intensified water circulation have significantly altered the distribution, extent, and state of ground temperature and groundwater. Spatial variations in these changes are influenced by surface and groundwater presence and flow patterns. Accelerated permafrost degradation and reduced seasonal soil freezing lead to a transition from a primarily frozen winter state to a partially thawed state with year‐round active groundwater flow paths. To capture spatial variations in changing cryo‐hydrogeological conditions, a multi‐source approach was employed, integrating in situ borehole and piezometer data with geophysical techniques including Ground Penetrating Radar (GPR) and Frequency Domain Electromagnetic Method (FDEM). The main goal was to identify unconfined and confined aquifers, and the permafrost table. Changes in the active layer thickness between areas with and without water influence were estimated. The findings contribute to the knowledge of high‐latitude hydrology and the impact of climate change on permafrost degradation and associated groundwater dynamics.