Firn aquifer properties of Wilkins ice shelf from multi-source spaceborne microwave observations

The potential impact of increased snowmelt and related hydrological processes on ice sheet stability has become a focus of academic attention. Hydro-fracture caused by liquid water is one of the main triggers of ice shelf disintegration. Recent discoveries of firn aquifer (FA) in the Wilkins Ice Shelf (WIS) have updated our understanding of surface hydrological processes, mass and energy balance. However, the limited field and airborne radar observations of FA cannot provide a complete picture of their distribution and characteristics. Microwave remote sensing is highly sensitive to the dielectric constant change caused by the dynamics in buried liquid water. However, it is challenging to obtain the buried depth of FA from space. In this study, the extent and depth to the water table (DWT) of FA are investigated with the combination of active and passive microwave observations, as well as airborne radar measurements. First, with the verification points from airborne radar, the extent of FA is mapped from satellite-derived snowmelt and accumulation conditions based on a K-Nearest Neighbors classification model (OA=97.2%, Kappa=0.94). Next, we use a Gaussian Process Regression model to estimate the DWT of FA (R=0.8, RMSE=2.17 m). The results show that FA occurred in most areas of WIS in 2014, with a DWT of 12.8±2.9 m. The DWT increased from north to south. Further study will examine the dynamics in FA and their hydro-fracture effect on ice shelf calving and the stability of the Antarctic ice sheet.