Abstract
The Barents Sea is one of the most rapidly changing Arctic regions in terms of sea ice. As it is almost ice-free in summer, most recent changes in the Barents Sea have occurred in winter, with a reduction of about 50% of its March sea-ice area between 1979 and 2018. This sea-ice loss is clearly linked to an increase in the Atlantic Ocean heat transport, especially through the Barents Sea Opening, in the western part of the Barents Sea. In this study, we investigate the links between the March Barents sea-ice area and ocean heat transport at the Barents Sea Opening using seven different coupled atmosphere-ocean general circulation models, with at least two different horizontal resolutions for each model. These models follow the High Resolution Model Intercomparison Project protocol, and we focus on the historical record (1950-2014). We find that all models capture the anticorrelation between March sea-ice area and annual mean ocean heat transport in the Barents Sea. Furthermore, the use of an increased ocean resolution allows to better resolve the different ocean pathways into the Barents Sea and the Atlantic Water heat transport at the Barents Sea Opening (reduced transect). A higher ocean resolution also improves the strong water cooling at the sea-ice edge and further formation of warm intermediate Atlantic Water. However, the impact of a higher ocean resolution on the mean March Barents sea-ice area and ocean heat transport at the Barents Sea Opening (large transect) varies among models. A potential reason for a different effect of model resolution on ocean heat transport when considering a reduced or a large transect is that the Atlantic Water and Norwegian Coastal Current inflows are under-represented at lower ocean resolution. Finally, we do not find a systematic effect of resolution on the strength of the sea-ice area - ocean heat transport relationship.
Highlights
Arctic sea ice has received a lot of attention in the past decades due to its strong decrease since the beginning of satellite observations (Barber et al, 2017; Walsh et al, 2017; IPCC, 2019)
We find that when the March Barents sea-ice area decreases with higher resolution for a given model configuration, the Ocean heat transport (OHT) at the Barents Sea Opening increases for that configuration (Table 3)
This study provides the first detailed multi-model comparison on the impact of model resolution on the sea-ice area and ocean heat transport (OHT) in the Barents Sea
Summary
Arctic sea ice has received a lot of attention in the past decades due to its strong decrease since the beginning of satellite observations (Barber et al, 2017; Walsh et al, 2017; IPCC, 2019). The total Arctic sea-ice extent decline has been strongest in summer, with 45% ice loss in September between 1979–1989 and 2017 (Stroeve and Notz, 2018). The reduction in sea-ice extent has been less pronounced in winter, with 11% ice loss in March between 1979–1989 and 2018 (Stroeve and Notz, 2018). Barents Sea Ice—Ocean Interactions (Kwok, 2018) This has led to a reduction in the fraction of multiyear sea ice, which covers less than one-third of the Arctic Ocean, compared to about 60% in the early 1980s (Kwok, 2018; Stroeve and Notz, 2018). As the different Arctic regions progressively become ice free in summer, future ice loss is projected to occur more and more in winter (Onarheim et al, 2018; Stroeve and Notz, 2018)
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