Materials and Methods

In-situ data: 

(a) Oceanographic survey

From Jul 2017 to Jul 2018, five oceanographic surveys were conducted on small boats along the first ~30 km offshore of the western Yucatan Peninsula coast to sample the seasonal variation of the thermohaline characteristics of the coastal ocean. Each survey took about one week to be completed and was planned three months apart from each other. This particular work presents the findings of the 5th campaign that occurred during summer 2018 (Jul 23- 28, Figure \ref{162479}). The vessels used in the surveys were equipped with a hand-held Valeport miniCTD factory-calibrated, and a Garmin GPS, to collect temperature, conductivity, and depth data, at all sampling stations. These data were later transformed to observations of conservative temperature (CT) and absolute salinity (SA) using the thermodynamic equation of seawater TEOS-10 toolbox \citep*{barker2011}.  To show the surface distribution of  SA and CT in the study region, surface samplings of these variables were optimum interpolated using the Data-Interpolating Variational Analysis software \citep{Troupin_2012}. All data were processed using the R software \citep{2014}.