Poleward ocean heat transports, sea ice processes, and Arctic sea ice variability in NorESM1-M simulations

Abstract

Results from the NorESM1-M coupled climate model were used to examine relationships between Arctic sea ice area and ocean heat transports through the primary Arctic gateways. Comparisons were made with two other models (CNRM-CM5 and MRI-CGM3) that are part of the CMIP5 archive which have the required outputs for calculating ocean heat transports. Based on an evaluation, NorESM1-M was found to be best suited to study the effects of heat transports on sea ice area, and conclusions are based on results from this model. The Arctic Ocean was divided into two regions, the Barents Sea and the Central Arctic Ocean. The sea ice area variability was further analyzed in terms of frazil and congelation growth, top and bottom melting, and heat transports in the Barents Sea Opening (BSO) and the Fram Strait (FS). In the Barents Sea, increased heat transport in the BSO has a strong influence on sea ice area in terms of reduced congelation growth, while bottom melting is important for the variability in the Central Arctic Ocean. The negative trend in sea ice area is considerably greater in the Barents Sea than in the Central Arctic Ocean, despite the Central Arctic Ocean area being much larger, and reflects the major trend in the BSO heat transport. The model results in this study suggest that the ocean has stronger direct impact on changes in sea ice mass in terms of freezing and melting than the atmosphere, both in the mean and with respect to variability.