Atmospheric Energy Sources for Winter Sea Ice Variability over the North Barents-Kara Seas

Anomalous poleward transport of atmospheric energy can lead to sea ice loss during boreal winter over the Arctic, especially in the North Barents-Kara Seas (NBKS), by strengthening downward longwave radiation (DLW). However, compared with the extensive studies of latent energy sources, those of sensible energy sources are currently insufficient. Therefore, we focus on the intraseasonal sea ice loss events from the perspectives of both energy forms. First, the contributions of latent and sensible energy to DLW and sea ice reduction are quantified using the lagged composite method, a multiple linear regression model, and an ice toy model. Second, a Lagrangian approach is performed to examine sources of latent and sensible energy. Third, possible underlying mechanisms are proposed. We find that the positive anomalies of latent and sensible energy account for approximately 56% and 28% of the increase in DLW, respectively, and the DLW anomalies can theoretically explain a maximum of 58% of sea ice reduction. Geographically, the North Atlantic, the Norwegian, North, and Baltic Seas, western Europe, and the northeastern Pacific are major atmospheric energy source regions. Additionally, while the contributions of latent energy sources decrease with increasing distance from the NBKS, those of sensible energy sources are concentrated in the midlatitudes. Mechanistically, latent energy can influence sea ice decline, both directly by increasing the Arctic precipitable water and indirectly by warming the Arctic atmosphere through a remote conversion into sensible energy. Our results indicate that the Rossby waves induced by latent heating over the western tropical Pacific contribute to anomalous energy sources at midlatitude Pacific and Atlantic both dynamically and thermodynamically. Significance StatementWinter sea ice retreat in the Arctic has been attributed to increasing poleward atmospheric energy transport. While latent energy sources are extensively examined in previous studies, studies on sensible energy sources remain limited. Considering both atmospheric energy forms, we detected energy sources for the intraseasonal sea ice-loss events in the winter NBKS. Geographically, the North Atlantic, the Norwegian, North, and Baltic Seas, western Europe, and the northeastern Pacific are predominant energy source regions. Mechanistically, Rossby waves in the Northern Hemisphere triggered by tropical latent heating contribute to warm and moist air intrusions into the Arctic. This work suggests that latent energy can impact Arctic sea ice directly by moistening the atmosphere and indirectly by warming the Arctic atmosphere through remote conversion into sensible energy.