Water masses in the Caribbean Sea and sub-annual variability in the Guajira upwelling region

Abstract

The study of water masses is important as they transport water properties affecting the biosphere and ocean dynamics. In this study, we revisit water masses in the Caribbean Sea using climatology and 11 months of observations at different depths from 3 moorings placed in the Guajira upwelling region, providing some new findings. The Caribbean Surface Water (CSW) seasonal variability is studied at the mixed layer depth. Salinity differences between CSW and the saltier North Atlantic Subtropical Underwater (SUW) determine static stability spatial and temporal variations, with implications for regional ocean dynamics. Besides, we assess the climatologic distribution of water masses below the salinity maximum using the optimum multiparameter analysis and the Thermodynamic Equation of Seawater 2010, defining their source water indices when entering the Caribbean Sea. The SUW, with its core at ~ 150 m depth, occupies 16% of the Caribbean Sea volume, complemented by 38% of Antarctic Intermediate Water, with its core at ~ 700 m depth and North Atlantic Deep Water, which as bottom water occupies 46% of the volume. Hydrographic observations do not differ from climatology, regardless of their large sub-annual variations decreasing with depth. Daily time series of dominant water fractions at different depths correlate at each mooring, indicating a common forcing. Besides, rotated wind stress, which is an indicator of the Guajira upwelling, correlates regularly with water mass fractions down to 700 m depth. However, during strong wind shifts, upwelling seems to affect them down to 1450 m depth.