An ice‐ocean model study of the mid‐2000s regime change in the Barents Sea

Over the satellite record, the Barents Sea winter maximum in sea ice extent has declined and was increasingly limited to areas north of the Polar Front after 2005 by warming Atlantic Water (AW) and Barents Sea Water (BSW). Sea ice extent here continues to garner interest, not least because it is associated with extreme winter weather in Europe and Asia. Previous model studies suggest there is a possibility that natural variability will cause southward re-expansion of the lost sea ice cover but reducing uncertainties requires a better understanding of the processes driving BSW variability. To address questions about BSW variability, we used a high-resolution model validated with observations over 1985-2014 to calculate the watermass transport, heat and freshwater budgets within the central Barents Sea, south of the Polar Front. The model shows BSW volume minima events in years centering at 1990 and 2004, meaning a reduction in the Barents Sea’s volume reservoir (also termed “memory”) of water that is consistent with historical BSW properties. Both events were preceded by extensive winter sea ice and substantial summer net sea ice melt. The event in 2004 was more extreme and led to warming AW occupying a greater volume in the Barents Sea after 2005. The reduced “memory” of BSW volume could impede a return to the more extensive winter sea ice regime and make further reduction in winter sea ice possible.Key PointsWe identify events of minimum dense water volume in the Barents Sea, with the 2002-2005 event being unique with large sea ice importDuring this event, a freshwater anomaly from sea ice melt enhanced the salinity gradient, reducing dense water formation and exportAfter the event in 2006-2014, the proportion of dense water present in the southern Barents Sea remained smaller than during 1985-2002Plain Language SummaryWinter sea ice in the Barents Sea, in the eastern Arctic Ocean, has been in decline, particularly since 2000. The sea ice extent in this region is associated with atmospheric weather conditions during winter in Europe and Asia. An important factor in understanding the sea ice retreat is understanding the variability in Barents Sea temperature and salinity. Using a high-resolution simulation, the source of variability in Barents Sea Water properties has been quantified. This shows two events, 1990 and 2004, when Barents Sea Water volume reduced, giving less “memory” of previous conditions. The event in 2004 was larger and followed a large net sea ice melt. The volume of Barents Sea Water present in the Barents Sea did not fully recover after 2005. This could make it more difficult for winter sea ice to return to the region