The mass balance of Antarctica is sensitive to intrusions of extremely warm, moist airmasses from the mid-latitudes in the form of atmospheric rivers (ARs). These storms provide a sub-tropical link to the Antarctic continent and create extreme atmospheric conditions that are largely consequential to surface melt, snowfall, and ice-shelf stability. Using an AR detection algorithm and regional climate simulations from MAR, both designed for polar regions, we characterize the AR life cycle and demonstrate their impacts on processes ranging from high snowfall events to surface-melt induced hydrofracturing.

Despite their rarity of occurrence over Antarctica (maximum frequency of ~3 days per year over a given point), ARs have a relatively large impact on the surface melt processes in West Antarctica and snowfall patterns across the whole continent. During the summer season along the Antarctic Peninsula ice shelves, AR landfalls lead to conditions (i.e. extreme temperatures, rainfall, surface melt, sea-ice clearing, ocean swell enhancement), that act to destabilize the leeward ice shelves. This occurs through a combination widespread surface-melt induced hydrofracturing and sea-ice clearing allowing storm enhanced swells to apply strain along the ice shelf front. Elsewhere higher on the plateau of the West Antarctic Ice Sheet, ARs and their associated moisture transport trigger surface melt in regions where such occurrences are a rarity. In East Antarctica, ARs are responsible for most of the heaviest precipitation events with ramifications for past climate reconstruction using ice cores. Despite ARs having a modest impact on total precipitation, annual snowfall trends across East Antarctic were primarily driven by trends in AR frequency while ARs controlled the inter-annual variability of precipitation across most of the Antarctic ice sheet from 1980-2018.

Our results suggest that ARs play a significant role in the Antarctic mass balance. Thus, any future changes in atmospheric blocking or tropical-polar teleconnections, which control AR behavior around Antarctica, may have significant impacts on future surface mass balance projections and subsequent sea level changes. Current research is exploring the origins of AR genesis and moisture pathways with a focus on the relationship between atmospheric blocking in the Southern Ocean and AR behavior over East Antarctica

about the speaker:

Jonathan Wille is currently a post-doctoral researcher with the l'Institut des Géosciences de l'Environnement at the Université Grenoble Alpes studying the connections between synoptic-scale atmospheric dynamics and mass balance over the polar ice sheets. Previously he received his B.S. degree at the University of Oklahoma in meteorology and M.S. degree at The Ohio State University studying Antarctic boundary-layer meteorology. After recently finishing a Ph.D. studying the climatology and impacts of atmospheric rivers in Antarctica, he continues to study this topic under the ANR-funded Atmospheric River Climatology in Antarctica (ARCA) project. The goal of the ARCA project is to create an understanding of atmospheric river behavior in the past and future. The past is studied using ice core records and direct δ¹⁸O measurements while the future is studied by applying a polar-specific atmospheric river detection algorithm to climate model simulations.