Pathways and hydrography in the Mesoamerican Barrier Reef System Part 2: Water masses and thermohaline structure

• Published in: Continental shelf research 2016-06, Vol.120, p.41-58
• Main Authors: Carrillo, L., Johns, E.M., Smith, R.H., Lamkin, J.T., Largier, J.L.
• Format: Article
• Language: English
• Subjects: 4220 (Coral reef systems); 4223 (Descriptive and regional oceanography); 4512 (Currents); 4520 (Eddies and mesoscale processes); Barriers; Circulation; Description of water masses in the Mesoamerican Barrier Reef System, with local influences due to upwelling and land runoff; Dynamical systems; Dynamics; Geostrophy; Hydrography; Mesoamerican Barrier Reef; Reefs; Rivers; Surface water; Thermohalines; Water masses; Yucatan Current
• ISSN: 0278-4343; 1873-6955
• DOI: 10.1016/j.csr.2016.03.014

Hydrographic data from two oceanographic cruises conducted during March 2006 and January/February 2007 are used to investigate the thermohaline structure related to the observed circulation along the Mesoamerican Barrier Reef System (MBRS). From our observations we identify three water masses in the MBRS: the Caribbean Surface Water (CSW), North Atlantic Subtropical Underwater (SUW), and Tropical Atlantic Central Water (TACW). Little vertical structure in temperature is observed in the upper 100m of the water column, but important differences are observed in the salinity distribution both horizontally and with depth. Freshwater inputs to the system from the mainland can be traced in the surface layer, with two possible sources: one from surface rivers located along the southern portion of the MBRS, and the other originating from an underground river system located along the northern portion of the MBRS. The thermohaline structure in the MBRS reflects the dynamics of the observed circulation. Uplifted isopycnals along most of the central and northern coastline of the MBRS reflect the effects of the strong geostrophic circulation flowing northward, i.e. the Yucatan Current. To the south along the MBRS, much weaker velocities are observed, with the Honduras Gyre dominating the flow in this region as presented during January/February 2007. These two regions are separated by onshore and divergent alongshore flow associated with the impingement of the Cayman Current on the shore and the MBRS. •Gives detailed description of thermohaline structure and water masses in the MBRS.•Thermohaline structure in the MBRS reflects dynamics of the observed circulation.•Isopycnals in the central and northern MBRS reflect the strong Yucatan Current.•Results show implications of the Cayman Current impingement latitude in the MBRS.•Freshwater inputs are present in the southern and northern regions of the MBRS.