Impact of model resolution on Arctic sea ice and North Atlantic Ocean heat transport

Arctic sea-ice area and volume have substantially decreased since the beginning of the satellite era. Concurrently, the poleward
heat transport from the North Atlantic Ocean into the Arctic has increased, partly contributing to the loss of sea ice.
Increasing the horizontal resolution of general circulation models (GCMs) improves their ability to represent the complex
interplay of processes at high latitudes. Here, we investigate the impact of model resolution on Arctic sea ice and Atlantic
Ocean heat transport (OHT) by using five different state-of-the-art coupled GCMs (12 model configurations in total) that
include dynamic representations of the ocean, atmosphere and sea ice. The models participate in the High Resolution Model
Intercomparison Project (HighResMIP) of the sixth phase of the Coupled Model Intercomparison Project (CMIP6). Model
results over the period 1950–2014 are compared to different observational datasets. In the models studied, a finer ocean
resolution drives lower Arctic sea-ice area and volume and generally enhances Atlantic OHT. The representation of ocean
surface characteristics, such as sea-surface temperature (SST) and velocity, is greatly improved by using a finer ocean resolution.
This study highlights a clear anticorrelation at interannual time scales between Arctic sea ice (area and volume) and
Atlantic OHT north of 60 ◦N in the models studied. However, the strength of this relationship is not systematically impacted
by model resolution. The higher the latitude to compute OHT, the stronger the relationship between sea-ice area/volume and
OHT. Sea ice in the Barents/Kara and Greenland–Iceland–Norwegian (GIN) Seas is more strongly connected to Atlantic
OHT than other Arctic seas.