Abstract

Most East Antarctic ice shelf cavities host cold water masses that limit basal melting, and only few short-term observational studies exist on what drives warm water intrusions into these cavities. We present nine years of continuous oceanographic records (2009-2019) from below Fimbulisen in Dronning Maud Land, East Antarctica. Joint analyses with oceanic and atmospheric forcing variables reveal the drivers of warm inflow variability into this ice shelf cavity. On monthly time scales, warm inflow events are associated with local westerly wind anomalies reducing downwelling in front of the ice shelf. In 2016, however, our observations show a statistically significant regime shift toward a more sustained warm inflow that persists until the end of the data record. During this period, at times, unmodified Warm Deep Water intrudes into the cavity. We find that this transition is linked to a reduction in coastal sea ice cover and a strengthening of remote subpolar westerlies. As a potential result of this enhanced warm inflow, a satellite-derived basal melt rate estimate of 0.62 m/year is nearly double the climatological basal mass loss at this cold ice shelf cavity. These results imply that East Antarctic ice shelves may become more exposed to warmer waters with a projected increase of circum-Antarctic westerlies, increasing this region’s relevance for sea level rise projections.