Antarctic Atmospheric River Climatology and Precipitation Impacts

The Antarctic ice sheet (AIS) is sensitive to short-term extreme meteorological events that can leave long-term impacts on the continent's surface mass balance (SMB). We investigate the impacts of atmospheric rivers (ARs) on the AIS precipitation budget using an AR detection algorithm and a regional climate model (Modele Atmospherique Regional) from 1980 to 2018. While ARs and their associated extreme vapor transport are relatively rare events over Antarctic coastal regions (similar to 3 days per year), they have a significant impact on the precipitation climatology. ARs are responsible for at least 10% of total accumulated snowfall across East Antarctica (localized areas reaching 20%) and a majority of extreme precipitation events. Trends in AR annual frequency since 1980 are observed across parts of AIS, most notably an increasing trend in Dronning Maud Land; however, interannual variability in AR frequency is much larger. This AR behavior appears to drive a significant portion of annual snowfall trends across East Antarctica, while controlling the interannual variability of precipitation across most of the AIS. AR landfalls are most likely when the circumpolar jet is highly amplified during blocking conditions in the Southern Ocean. There is a fingerprint of the Southern Annular Mode (SAM) on AR variability in West Antarctica with SAM+ (SAM-) favoring increased AR frequency in the Antarctic Peninsula (Amundsen-Ross Sea coastline). Given the relatively large influence ARs have on precipitation across the continent, it is advantageous for future studies of moisture transport to Antarctica to consider an AR framework especially when considering future SMB changes. Plain Language Summary The Antarctic continent, like many deserts in the world, receives a large percentage of its yearly precipitation from just a few intense precipitation events. Atmospheric rivers (ARs), narrow corridors of intense moisture transporting moisture from low to high latitudes, are commonly associated with heavy rain and snowfall in the midlatitudes like the west coasts of North/South America and Europe. In Antarctica, ARs are rarer with most near-coastal regions in Antarctica experiencing AR conditions a few days per year but still have a major influence on the surface mass balance of the ice sheet. ARs are responsible for 10%-20% of the total snowfall across East Antarctica. Although a modest percentage, this contribution to the snowfall budget is the component that has been driving parts of the positive annual snowfall trends in Dronning Maud and negative trends in Wilkes Land. Also, ARs control the year-to-year variability of precipitation across most of the ice sheet. Given the link between ARs and snowfall accumulation trends, increased future AR activity would result in higher snowfall accumulation on the Antarctic continent and possibly offset some sea-level rise from dynamic ice loss, but this must be considered in balance with increased melting frequency already documented with ARs. Key Points Atmospheric rivers in Antarctica are rare events but are a key contributor to the ice sheet's surface mass balance Their impact on precipitation is most pronounced in East Antarctica where they are responsible for a majority of extreme precipitation events Atmospheric rivers are contributing to modern snowfall trends and controlling overall precipitation variability across Antarctica

Automated summary

The Antarctic ice sheet is sensitive to atmospheric rivers (ARs) which have a significant impact on precipitation in East Antarctica, driving snowfall trends and controlling precipitation variability across most of the ice sheet. Increased future AR activity may result in higher snowfall accumulation on the continent.