Abstract
This study evaluated the performance of 15 CMIP6 models, using ORAS5 and GLORYS12V1 as reference datasets, in simulating current velocity, seawater temperature, salinity, as well as the associated volume transport, ocean heat transport, and freshwater transport in the Bering Strait region. Based on the evaluation results, it then projected future changes in water transports. ORAS5 and GLORYS12V1 show broadly similar spatial patterns in current velocity, seawater temperature, and salinity, while the CMIP6 models exhibit notable inter-model spread. The comprehensive evaluation revealed considerable variability in model performance for current velocity, temperature, and salinity. Estimates of volume transport, ocean heat transport, and freshwater transport aligned with two reanalysis datasets in their seasonal variations, while most models underestimated those transports. The analysis identified differences in the well-performing models for each transport. Ensemble experiments with different numbers of well-performing models determined reasonable schemes for projections of future inflow transports. Under SSP2–4.5 and SSP5–8.5 scenarios, volume and freshwater transport showed declining trends, while ocean heat transport increased, with trends being more pronounced under SSP5–8.5. The multi-model mean based on well-performing models exhibited differences in trend values compared with the ensemble of all unassessed models. The relationship between the horizontal and vertical resolutions of the models and their estimates of volume transport, ocean heat transport, and freshwater transport was also examined. This study deepens the understanding of the ability of CMIP6 models to simulate ocean dynamics in the Bering Strait region and provides new insights into potential future changes in Pacific inflow.
•Notable inter-model spreads exist in seawater properties and associated transports.•Declining trends in future volume and freshwater transport under SSP2-4.5/SSP5-8.5.•Future ocean heat transport shows an increasing trend under SSP2-4.5 and SSP5-8.5.•Optimized ensembles show a slower volume decline than the full-model ensemble mean.•Optimized ensembles show weaker ocean heat rise and faster freshwater decline.