The (MDVs) are an ice-free area of Antarctica characterized by a permafrost landscape with glacial meltwater streams that flow for 6-12 weeks during the austral summer. In the hyporheic zones beneath stream channels, the active layer can be extensive, ranging from a few centimeters from the surface to over half a meter in depth. The thaw and refreeze of the active layer under and adjacent to stream channels have important implications on hyporheic exchange and associated ecological and chemical properties of the stream ecosystems. This study aims to characterize the relationship between streamflow and hyporheic active layer dynamics by comparing long-term records of streamflow with soil sensor measurements (temperature, moisture, and salinity) in two streams in the MDVs. In addition to these records, field measurements of permafrost depth and channel morphology were collected to add context to sensor data. Here we analyze the controls on depth and duration of thaw in the hyporheic zones by comparing relationships among meteorological variables, streamflow, and subsurface conditions between hyporheic and dry subsurface locations. Preliminary results suggest that meltwater plays an important role in promoting and maintaining thaw. Further, the timing of active layer thaw and refreeze are at least partly correlated with the beginning and end of flow, respectively. These results point to the importance of liquid water in facilitating subsurface ecological processes in the MDVs and beyond, a major consideration for an increasingly warmer Antarctic climate.
