Atmospheric River Impacts on Greenland Ice Sheet Surface Mass Balance

Abstract

Greenland Ice Sheet (GrIS) mass loss has accelerated since the turn of the twenty‐first century. Several recent episodes of rapid GrIS ablation coincided with intense moisture transport over Greenland by atmospheric rivers (ARs), suggesting that these events influence the evolution of GrIS surface mass balance (SMB). ARs likely provide melt energy through several physical mechanisms, and conversely, may increase SMB through enhanced snow accumulation. In this study, we compile a long‐term (1980–2016) record of moisture transport events using a conventional AR identification algorithm as well as a self‐organizing map classification applied to MERRA‐2 data. We then analyze AR effects on the GrIS using melt data from passive microwave satellite observations and regional climate model output. Results show that anomalously strong moisture transport by ARs clearly contributed to increased GrIS mass loss in recent years. AR activity over Greenland was above normal throughout the 2000s and early 2010s, and recent melting seasons with above‐average GrIS melt feature positive moisture transport anomalies over Greenland. Analysis of individual AR impacts shows a pronounced increase in GrIS surface melt after strong AR events. AR effects on SMB are more complex, as strong summer ARs cause sharp SMB losses in the ablation zone that exceed moderate SMB gains induced by ARs in the accumulation zone during summer and in all areas during other seasons. Our results demonstrate the influence of the strongest ARs in controlling GrIS SMB, and we conclude that projections of future GrIS SMB should accurately capture these rare ephemeral events.

Observing and Modeling Ice Sheet Surface Mass Balance

“…In general, coastal regions receive most of their precipitation from nearby ocean areas, while high‐elevation snowfall is sourced from remote, lower‐latitude regions, especially on the AIS (Delaygue et al, ; Sodemann & Stohl, ). The largest precipitation events are caused by “atmospheric rivers,” long‐fetched channels of high atmospheric moisture that protrude from the tropics or midlatitudes all the way to high latitudes (Gorodetskaya, Tsukernik, et al, ; Mattingly et al, ; Nash et al, ). In middle‐ and high‐elevation areas of the AIS, atmospheric rivers generate 30–100% of the annual precipitation (Gorodetskaya et al, ; Schlosser et al, ), depending on their strength, location, and frequency.…”

Spatial Shift of Greenland Moisture Sources Related to Enhanced Arctic Warming

“…Changes in GrIS mass balance coincide with recent increases in global temperature, with larger increases in the Arctic (Hartmann et al, ). The largest contribution to the recent changes in SMB has been suggested to be changes in atmospheric circulation over the ice sheet, contributing to up to 70% of the surface mass loss (Fettweis et al, ; Hofer et al, ; Mattingly et al, ; Tedesco et al, ). The changes in atmospheric circulation are characterized by anomalous anticyclonic circulation, higher 500 hPa geopotential height (Hanna et al, ), and a northward shift in the jet stream location (Tedesco et al, ).…”

“…The changes in atmospheric circulation are characterized by anomalous anticyclonic circulation, higher 500 hPa geopotential height (Hanna et al, ), and a northward shift in the jet stream location (Tedesco et al, ). Various mechanisms for the impact of the circulation change on mass loss have been suggested, including changes in air temperature (Fettweis et al, ), reductions in cloud cover (Hofer et al, ), and atmospheric river events bringing moisture over the ice sheet (Mattingly et al, ).…”

The Role of Atmospheric Rivers for Extreme Ablation and Snowfall Events in the Southern Alps of New Zealand

“…ARs have been recognized as significant large-scale drivers of flood events in the midlatitudes, particularly in North America (e.g., Ralph et al, 2006) and Europe (e.g., Lavers et al, 2011). There has also been some investigation of the role of ARs in driving both high ablation and accumulation events in international glacier-climate research, in the Sierra Nevada (Guan et al, 2010), Canadian Arctic (Dolant et al, 2017), and the Greenland ice sheet (Mattingly et al, 2018)-but not yet in New Zealand.…”