Mapping Basal Melt Under the Shackleton Ice Shelf, East Antarctica, From CryoSat-2 Radar Altimetry

Ice shelvesbuttress the fast-flowing glaciers draining ice sheets, so changes in the ice shelves may alter the buttressing effect and the discharge of grounded ice, therefore influencing sea level. Basal melting of the ice shelves would reduce their ability to restrain the discharge of grounded ice into the ocean. However, estimating the basal melt rate is challenging due to the large uncertainty in the calculation. In this study, we use a Lagrangian framework to improve the basal melt rate derivation and apply the method to the Shackleton ice shelf as a case study. We use the CryoSat-2 data to characterize the spatial distribution patterns of ice shelf surface elevation changes between 2010 and 2018. Combining these results with the ice surface velocity and output from the regional climate model, we obtain a map of the basal melt rate and calculate the total and average basal mass balance. The total basal meltwater production for the Shackleton ice shelf is 54.6 +/- 7.2 Gt/yr. The highest melt rates, which exceed 50 m/yr, are found close to the grounding line and the main trunk of Denman glacier. Based on the analysis, we show that the Lagrangian method can provide more spatially coherent patterns of ice shelf surface elevation changes and reduce the uncertainty in basal melt rate calculation.