The Gulf of Tehuantepec (GT), in the Mexican eastern tropical Pacific is mainly known by the northerly winds events that occur every winter, and produce a series of physical and biological responses accompanying wind driven mesoscale eddies. During summer however, the transit of tropical disturbances and wind direction reversals due to the position of the ITCZ in relation to the GT, lead to the predominance of zonal winds. Mesoscale eddies occupying the GT during this time; originate mainly due to the perturbation to the depth of the thermocline that zonal wind can produce at the western Central America coast. The relative position of each eddy allow the flow of relatively low temperature and salinity water (the Costa Rica Coastal Current) into and throughout the GT, converging at about Puerto Angel, with relatively high temperature and salinity water moving from the west. Although the GT can experience net surface heat flux losses during winter, in the western margin of the Gulf of Tehuantepec, the net surface heat flux is positive throughout the year and correspondingly there is an export of advective heat along the year from the water column. Large advective heat losses, in February and October occur, when observed southeastward coastal currents are strong. Small losses occur, in May and January, when coastal currents are weak and towards different directions. Currents arriving to the area from the west seem to correspond to a tropical branch of the California Current in February. In October, however, similar currents seem to be part of the Costa Rica Coastal Current after leaving the Tehuantepec Bowl.
