Atmosphere–Ocean–Sea Ice Feedbacks Sustain Recent Barents Sea Ice Loss despite Cooler Atlantic Water Inflow

Abstract

Abstract Winter sea ice cover has declined faster in the northern Barents Sea (NBS) than in the rest of the Arctic Ocean. One of the key elements controlling sea ice extent in the NBS is the inflow of warm and saline Atlantic water (AW) through the Barents Sea Opening. We show that despite a pronounced decadal variability in the AW temperature with a cooling trend since the mid-2000s, sea ice in the NBS continues to decline. We find that the sea ice decline is partly caused by reduced oceanic heat loss in the southern Barents Sea (SBS) and subsequent transport of warmer AW downstream to the NBS. Moreover, reduced heat loss contributes to increased sea surface height (SSH) in the SBS and sets up a meridional SSH gradient between SBS and NBS. This reduces the inflow of colder Arctic waters from the eastern Barents Sea, which contributes to further warming in the NBS. Results from idealized coupled climate model experiments with reduced Arctic sea ice suggest that these observed features can be driven by sea ice loss. Thus, despite the AW cooling trend, positive feedback from sea ice loss in the NBS, which involves reduced oceanic heat loss in the SBS and less inflow of cold Arctic waters, favors a continuous decline of sea ice in the NBS. Significance Statement Barents Sea region of the Arctic, with the largest changes in terms of atmospheric warming and sea ice loss, is of crucial importance not only for the Arctic region but also has potential implications for weather and climate in midlatitudes and the tropics. Here, in this study, we employ comprehensive approach with observational datasets and climate model experiments to identify recent on-going changes in Barents Sea climate and highlight the importance of sea ice loss in it.