A new vision of Antarctic surface melt: high-resolution observations from active and passive microwave satellites

Strong surface melting is an important precursor for ice shelf collapse, as observed in recent decades on the Antarctic Peninsula and projected via ice sheet models across Antarctica over this century. Accurate prediction of future melt evolution, and thus sea-level rise estimates, requires a robust, processed-based understanding of melt owing to important nonlinearities in the melt response to a warming atmosphere. Here we present new, high-resolution observations of Antarctic surface melt from both active and passive microwave satellite sensors. First, we are developing 40-m resolution surface melt observations using C-band synthetic aperture radar (C-SAR) backscatter from the Sentinel-1 A and B satellites. Given such high spatial resolution, these data are particularly useful for highlighting local and regional-scale processes driving melt, including the influence of fohn winds across Larsen C ice shelf on the Antarctic Peninsula. However, gaps in the Sentinel-1 record across space and time limit its utility in detecting melt for some ice shelves and melt seasons, and notably, the combined Sentinel-1 A/B time series provides data only back to April 2016. We are therefore in tandem developing observations of melt utilizing the recently-released NASA MEaSUREs enhanced-resolution passive microwave data product. Though these melt observations are far coarser resolution (3.125 - 6.25-km), they provide near-daily continent-wide coverage extending back to 1978 and are of much higher spatial resolution than previously-published Antarctic surface melt datasets. In combination, our new melt observations provide important insights into the coupling between the atmosphere, meltwater production, firn conditions, and ice sheet surface hydrology, all processes critical to quantify for improved sea-level projections.