Interplay of atmosphere and ocean amplifies summer marine extremes in the Barents Sea at different timescales

Marine extremes are recognized to cause severe ecosystem and socioeconomic impacts. However, in polar regions, such as the Barents Sea, the driving mechanisms of these extremes remain poorly understood and require careful consideration of the observed long-term ocean warming. Here we show that on short time scales of a few days, marine heatwaves and marine cold spells are dynamically driven by a dipole atmospheric circulation pattern between the Nordic Seas and the Barents Sea. Importantly, the dipole’s eastern component determines anomalies in shortwave radiation and latent heat fluxes. On interannual time scales, both changes in ocean heat supply and persistent atmospheric patterns can support severe marine extremes. We apply conventional marine heatwave detection methodology to OISSTv2 data, for the period of 1982–2021, and combine the analysis with ERA5 data to identify drivers. The ocean-atmosphere interplay across scales provides valuable information that can be integrated into fisheries and ecosystem management frameworks. On timescales of a few days, summer marine heatwaves in the Barents Sea are amplified mainly by an eastern high pressure system, and cold spells by an eastern low pressure system, according to analyses of observed sea surface temperatures over the past four decades.