CARIB12: A regional Community Earth System Model/Modular Ocean Model 6 configuration of the Caribbean Sea

A new Community Earth System Model/Modular Ocean Model 6 (CESM/MOM6) ocean-only regional 1/12° configuration of the Caribbean Sea is presented and validated. The model configuration was developed as a response to the rising need for high-resolution models for climate impact applications. The configuration is validated for the period covering 2000–2020 against ocean reanalysis and a suite of observation-based datasets. Particular emphasis is paid to the configuration's ability to represent the dynamical regime and properties of the region across sub-seasonal, seasonal, and inter-annual timescales. Near-surface fields of temperature, salinity, and sea surface height are well represented. In particular, the seasonal cycle of sea surface salinity and the spatial pattern of the low salinity associated with the Amazon and Orinoco river plumes is well captured. Surface speeds compare favorably against reanalysis and show that the mean flows within the Caribbean Sea (CS) are well represented. The model reproduces known pathways and timing for river plume waters intruding the region. The seasonal cycle of the mixed-layer depth is also well represented, with biases of <3 m when comparing to ocean reanalysis. The vertical structure and stratification across the water column is represented favorably against ship-based observations, with the largest simulated biases in the near-surface water mass and the sub-surface salinity maximum associated with the sub-tropical underwater mass. The temperature and salinity variability in the vertical structure is well represented in the model solution. We show that mean ocean mass transport across the multiple passages in the eastern Caribbean Sea compares favorably to observation-based estimates, but the model exhibits smaller variability and underestimates the mean Yucatán Channel transport when compared to observations and ocean reanalysis estimates. Furthermore, a brief comparison against a 1° CESM global ocean configuration shows that the higher-resolution regional model better represents the extent and seasonality of the Amazon River plume and hence better represents near-surface salinity and mixed-layer depth in the CS. Overall, the regional model reproduces the processes within the Caribbean Sea to a good degree and opens the possibility of regional ocean climate studies in support of decision-making within CESM.