Expanding Influence of Atlantic and Pacific Ocean Heat Transport on Winter Sea‐Ice Variability in a Warming Arctic

Abstract

The gradual anthropogenic‐driven retreat of Arctic sea ice is overlaid by large natural (internal) year‐to‐year variability. In winter, sea‐ice loss and variability are currently most pronounced in the Barents Sea. As the loss of winter sea ice continues in a warming world, other regions will experience increased sea‐ice variability. In this study, we investigate to what extent this increased winter sea‐ice variability in the future is connected to ocean heat transport (OHT). We analyze and contrast the present and future link between Pacific and Atlantic OHT and the winter Arctic sea‐ice cover using simulations from seven single‐model large ensembles. We find strong model agreement for a poleward expanding impact of OHT through the Bering Strait and the Barents Sea under continued sea‐ice retreat. Model differences on the Atlantic side can be explained by the differences in the simulated variance of the Atlantic inflows. Model differences on the Pacific side can be explained by differences in the simulated strength of Pacific Water inflows, and upper‐ocean stratification and vertical mixing on the Chukchi shelf. Our work highlights the increasing importance of the Pacific and Atlantic water inflows to the Arctic Ocean and highlights which factors are important to correctly simulate in order to capture the changing impact of OHT in the warming Arctic.

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

“…On the other hand, the difference between CESM-LE and reanalysis data could be related to biases in the CESM-LE. Even though CESM1 is among the best performing models in simulating Arctic sea-ice variability (Årthun et al, 2019;Dörr et al, 2024;England et al, 2019), it has a cold bias in the BKS (Figures 1a and 1c). This delays the sea-ice loss and the associated weakening of the oceanic influence compared to reanalysis and we would expect the oceanic influence to be stronger in CESM-LE than in reanalysis data for the recent decades, as is seen.…”

Drivers of summer Arctic sea-ice extent in CMIP6 large ensembles revealed by information flow

“…The previous winter sea-ice extent and volume are important in setting the course of the following summer sea-ice extent 24,29 . Furthermore, ocean heat transport to the Arctic, mainly via the Barents Sea Opening, Fram Strait and Bering Strait, has been shown to strongly impact Arctic sea ice 5,[30][31][32][33][34][35] , although this influence mainly occurs in winter 25,36,37 , when the sea-ice pack is more extensive.…”