Sentinel-1 Detection of Seasonal and Perennial Firn Aquifers in the Antarctic Peninsula

In recent years, the existence of firn aquifers in the Antarctic Peninsula (AP) has been confirmed by in situ observations. Due to their importance for understanding the hydrology of the Antarctic ice sheet, a more spatially comprehensive assessment of AP firn aquifers is desirable. The purpose of this study is to map firn aquifers in the AP from space using C-band Synthetic Aperture Radar imagery from ESA's Sentinel-1 mission. This product enables the detection of firn aquifers at 1 km2 resolution for the period 2017 to 2020. The method is based on quantifying the characteristic shape of the backscatter curve over time during the (partial) refreezing of the liquid water in the firn layer after each peak melt season. In this context, both seasonal aquifers and perennial aquifers are detected together, acknowledging that their backscatter signature in any given year is indistinguishable with the given method. With the new method, seasonal firn aquifers are being detected in the north and northwest of the AP, as well as on the Wilkins Ice Shelf and the George VI Ice Shelf. Imposing the aquifers to occur during all available years, as a proxy for perennial firn aquifers, limits their extent to the north and northwest AP. Both distributions agree well with model simulations. Further in situ and modelling studies and longer time series of satellite observations are needed to validate the results of this study.