Causal Links Between Sea‐Ice Variability in the Barents‐Kara Seas and Oceanic and Atmospheric Drivers.

The sea‐ice cover in the Barents and Kara Seas (BKS) displays pronounced interannual variability. Both atmospheric and oceanic drivers have been found to influence sea‐ice variability, but their relative strength and regional importance remain under debate. Here, we use the Liang‐Kleeman information flow method to quantify the causal influence of oceanic and atmospheric drivers on the annual sea‐ice cover in the BKS in the Community Earth System Model large ensemble and reanalysis. We find that atmospheric drivers dominate in the northern part, ocean heat transport dominates in the central and northeastern part, and local sea‐surface temperature dominates in the southern part. Furthermore, the large‐scale atmospheric circulation over the Nordic Seas drives ocean heat transport into the Barents Sea, which then influences sea ice. Under future sea‐ice retreat, the atmospheric drivers are expected to become more important. Plain Language Summary: The sea ice in the Barents and Kara Seas (BKS) is melting due to Arctic warming, but this is overlaid by large natural variability. This variability is caused by variations in the ocean and the atmosphere, but it is not clear which is more important in which parts of the region. We use a relatively new method that allows us to quantify cause‐effect relationships between sea ice and atmospheric and oceanic drivers. We find that in the north of the BKS, the atmosphere has the biggest impact, in the central and northeastern parts, it is the heat from the ocean, and in the south, it is the local sea temperature. We also find that wind patterns over the Nordic Seas affect how much oceanic heat comes into the Barents Sea, and that, in turn, affects the sea ice. Looking ahead, as the ice is expected to melt more in the future, the atmosphere is likely to become more important in driving sea ice variability in the BKS. This study helps us better understand how the ocean and atmosphere work together to influence the yearly changes in sea ice in this region. Key Points: Ocean heat transport drives sea‐ice variability in the central and northeastern Barents SeaAtmospheric temperature drives sea‐ice variability in the northern Barents‐Kara SeasAtmospheric circulation over the Nordic Seas drives ocean heat transport, which then influences sea‐ice variability [ABSTRACT FROM AUTHOR]