Major Surface Melting over the Ross Ice Shelf, Antarctica

Over the past three decades, West Antarctica (WA), especially the Ross Ice Shelf (RIS), has experienced more frequent surface melting during austral summer, which can cause potential ice loss in the future. This research investigates 4 extensive melt events over the RIS (1982/83, 1991/92, 2005 and 2016 cases) based on Polar WRF (PWRF) simulations driven by ERA5 reanalysis data and Moderate Resolution Imaging Spectroradiometer (MODIS) observed albedo. Compared to Antarctic Mesoscale Prediction System (AMPS), PWRF outputs significantly reduce the cold bias near the surface by ~2 ºC. In this research, three major regional rivers, direct warm advection, recurring foehn effect, and cloud introduced radiative impacts are identified and quantified based on PWRF outputs, ERA5 reanalysis data, and Clouds and the Earth's Radiant Energy System (CERES) satellite data. First, the direct warm air advection usually affects the coastal area and rarely results in strong melting. However, the moisture brought over the continent can benefit cloud formation, especially low-level liquid clouds, and thus impact the surface energy balance via increasing downward longwave radiation. Second, for 3 of 4 melt cases, more than 50% of the melting period experiences foehn warming that contribute 2 – 4 ºC increase in surface temperature. And the foehn effect can be amplified by strong moist imports from the ocean to coastal Marie Byrd Land (MBL). Third, under the impact of direct warm air advection and foehn effect, the cloud conditions can affect the surface energy balance via low-level liquid cloud formation or clear sky conditions. Additionally, the decreasing surface albedo caused by the surface melting increases the net shortwave radiation and promotes the expansion of the melting over the middle RIS and western MBL. For future research, the prediction of the stability of West Antarctic Ice Shelves should not only consider the large-scale climatic modes but also regional drivers. And the detailed physical mechanisms have a significant influence on the accuracy of the prediction.