Ice Sheet Surface and Subsurface Melt Water Discrimination Using Multi‐Frequency Microwave Radiometry Geophysical Research Letters

For understanding englacial hydrology and its impact on ice sheet mass balance, observations of the liquid water content (LWC) within the ice sheets are needed. We combined 1.4–10.7 GHz passive microwave measurements with traditional 18.7–36.5 GHz measurements to detect subsurface LWC. In situ measurements from the DYE-2 experiment site in Greenland and a modeled LWC at this site were used to calibrate and validate the method. Our analysis showed sensitivity of the lower microwave frequencies to LWC in surface and subsurface layers down to at least 2 m, enabling detection of seasonal subsurface LWC and its refreezing. A simplified retrieval detected a delayed refreezing of subsurface LWC following surface freezing, while also capturing total seasonal meltwater production. These advancements open the door to detection of subsurface meltwater and refreezing twice a day at pan-Greenland scale, thereby enabling improved estimates of ice sheet contributions to global sea level rise.