Mass Recharge of the Greenland Ice Sheet driven by an IntenseAtmospheric River

Atmospheric rivers are transient channels of intense water vapor that account for up to 90% of the poleward moisture transport from mid-latitudes. Though short-lived, these events can deliver extreme amounts of heat and rainfall that have been widely reported to accelerate ablation and ice mass loss across the Arctic. However, the impact of atmospheric river fueled snowfall has received less attention, partly due to the limited availability of empirical evidence and direct observations. Here, we explore the potential of atmospheric rivers to deliver intense snowfall to the Greenland ice sheet and thereby replenish its health through enhanced mass accumulation. Specifically, we use new firn-core isotopic analyses and glacio-meteorological datasets from Southeast Greenland to examine the origin and impact of atmospheric rivers on regional mass balance. To this end, we sampled firn core stratigraphy from the upper accumulation area of Southeast Greenland and related it to meteorological observations, to demonstrate that an intense atmospheric river in mid-March 2022 delivered up to 11.6 gigatons per day of extreme snowfall to this region of the ice sheet. 
We show that this immense snowfall not only recharged the snowpack and offset Greenland ice sheet net mass loss by 8% in 2022, but also raised local albedo thereby delaying the onset of summer bare-ice melt by 11 days, despite warmer than average spring temperatures. Since 2010, synoptic analysis of ERA5 data reveals that snow accumulation across Southeast Greenland increased by 20 mm water equivalent per year, driven by enhanced Atlantic cyclonicity. Depending on their seasonal timing, our study demonstrates that the impact of atmospheric rivers on the mass balance of the Greenland ice sheet is not exclusively negative. Moreover, their capacity to contribute consequential ice mass recharge may become increasingly significant under ongoing Arctic amplification and predicted poleward intrusion of mid-latitude moisture.