Thermohaline and current variability off the west Yucatan peninsula coast

Abstract

Thermohaline and current variability for a certain period in the first ∼40 km off the western Yucatan Peninsula were analyzed, from five hydrographic campaigns carried out between 2017 and 2018, and 2.5 years of two moored current meters and satellite wind observations. Three different coastal environments in the study region create local particularities important to the thermohaline variations: mangrove forests, coastal lagoons, and river or groundwater discharges. The thermohaline variability presented a seasonality marked principally by the salinity balances and by the temperature heating/cooling cycles. Seawater was commonly saltier near the coast, principally in spring (dry epoch) when there is an increase in evaporation. The type of waters identified were modified versions of the Caribbean water masses, where precipitation/evaporation balances, along with the wind forcing, mixed them with the near-coastal local fluxes. Dimensional analysis showed that bottom friction was not negligible (Ek > 1), and that water column stratification constrained the flow (Ri > 1). Currents off Campeche and Sisal flowed west-southwest and showed low coherency between sites, due to the different coastline orientations. Their predominant force was the wind stress, but bottom friction affected them, supported by the Ekman surface and bottom layers intersection. Ekman surface layer was commonly deeper than the actual depth, therefore Ekman spiral cannot develop completely, hence currents had an angle to the right of the direction of the winds of 72° (42°) in Campeche (Sisal). These flows were moderately coherent and in phase with the wind stress, at periods of 5 (18) days, respectively.