Arctic Atmospheric Rivers: An in-depth Investigation of their Impact on the Surface Energy Budget

Atmospheric Rivers (ARs) play a critical role in the Arctic climate system, providing the majority of water vapor transport into the Arctic. The potential of such events to impact especially the ice-covered regions of the Arctic have been explored in recent studies: ARs can trigger surface melt of the Greenland ice sheet and slow the seasonal recovery of the Arctic ice sheet. Furthermore, the low Arctic sea-ice extents of the years 2012 and 2020 could be linked to a more frequent occurrence of ARs. These case studies highlight the warming effect of individual cases of ARs.

We statistically investigate the warming effect of ARs on the Arctic sea-ice and ocean surface by examining anomalies in the atmospheric part of the surface energy budget (SEB). This climatological analysis is based on the ERA5 reanalysis from 1979 to 2021. ARs are detected using the algorithm by Guan and Waliser. Overall, a net energy gain of the surface associated with the occurrence of ARs is found, with the highest anomalies in winter over the open ocean. For a deeper understanding of the impact, complementary information on the climatological relevance of these events for the SEB is provided. Furthermore, we analyze the physical processes leading to the AR-related SEB anomalies, explaining the seasonal changes and the dependence of the anomalies on the surface type.

Within the rapidly changing Arctic climate, also changes in AR occurrence and their impact on the SEB can be expected. We investigate these changes by comparing the “old Arctic” (1979-1999) with the “new Arctic” (2000-2021). An overall increase in the occurrence frequency of ARs is found. Changes in the AR-related SEB anomalies are mostly linked to sea-ice decline.