Recent Intensification of Arctic Winter Anticyclonic Circulation Linked to Local Sea Ice Loss and SST Warming

The Arctic winter has experienced a strengthening anticyclonic anomaly over the Barents-Kara Sea (BKS) since the satellite era, driving substantial sea ice loss and warming in the region and cooling in Eurasia. However, the mechanisms behind this circulation anomaly remain uncertain. Using both observations and model simulations, we show that local sea ice loss and sea surface temperature warming are key contributors, explaining approximately 47% of the anomaly. These processes amplify local tropospheric warming relative to other Arctic regions, enhancing the horizontal gradient in thermal expansion and raising geopotential heights aloft, thereby strengthening the anticyclonic anomaly. Combined with evidence that the BKS anticyclonic anomaly itself drives local sea ice loss and warming, our results suggest a positive feedback loop, where the anomaly amplifies sea ice loss and warming, which in turn strengthens the anomaly. Although atmosphere-only models cannot fully capture these feedbacks due to the lack of interactive ocean and sea ice components, they underscore the crucial role of local forcing in amplifying the circulation anomaly. These results challenge the view that the BKS anomaly is primarily internally generated and largely independent of sea ice loss. Under continued greenhouse warming, the BKS anticyclonic anomaly is likely to further strengthen, with important implications for climate in the Arctic and beyond.