CARIB12: A Regional Community Earth System Model / Modular Ocean Model 6 Configuration of the Caribbean Sea

Abstract. A new 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 of 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 the mean flows within the Caribbean Sea are well represented. We performed a case study to examine the origin of waters arriving to the Virgin Islands Basin and show 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 less than 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 of the vertical structure is well represented in the model solution. We show that mean ocean mass transports across the multiple passages in the eastern Caribbean Sea compare favorably to observation-based estimates, but the model exhibits smaller variability compared to ocean reanalysis transport estimates. Furthermore, a brief comparison against a 1° CESM global ocean configuration shows that the higher resolution regional model improves significant biases in sea-surface salinity and mixed layer depth in particular. Additionally, the regional model better represents important features and variability within the Caribbean Sea compared to the 1° model. Overall, the regional model reproduces to a good degree the processes within the Caribbean Sea and opens the possibility of regional ocean climate studies in support of decision making within CESM.