Surface Salinity Balance in the Tropical Pacific Off Mexico

Abstract

A simplified analytical model was used to solve the salinity balance equation and study the relative contributions of freshwater flux and salt advection to the salinity tendency between the Gulf of Tehuantepec and Cabo Corrientes (14–22°N). The model used climatological mixed‐layer salinity, satellite‐derived geostrophic velocity and evaporation minus precipitation data in a four‐domain scheme. The mean circulation derived from the model largely coincides with previous reports and suggests that, in the steady state, the Mexican Coastal Current is decoupled from the Tehuantepec region. The analysis of the time‐dependent variability showed that the salt advection can be largely explained by the annual variations of the alongshore velocity (corresponding with the Mexican Coastal Current) and an average salinity. At the seasonal scale, the salt advection and the freshwater flux have similar contributions to the resulting salinity tendency. Near Tehuantepec, due to a local salinity regime, the analytical model does not represent well the observations, while in Manzanillo and Zihuatanejo the agreement between the model and the observations is good in both amplitude and phase. The accuracy of the model in representing the observations is improved in the first third of the year by inclusion of the semiannual scale and the nonlinear processes in the equation of salt advection.

Distribution of calanoid copepods across the mesoscale frontal zone of tropical-subtropical convergence off México

“…1) formed part of a system of fronts resulting from the transport of waters of different origins by the tropical branch of the California Current and by the Mexican Coastal Current. The former transports subpolar water to tropical latitudes (Godínez et al, 2010;Portela et al, 2016), while the latter transports tropical waters poleward (Willett et al, 2006;Portela et al, 2018). These current systems converge in and around the study area, where they mix and interact with Gulf of California waters intensifying the mesoscale processes in the region (Fiedler and Talley, 2006;Portela et al, 2018).…”

“…The former transports subpolar water to tropical latitudes (Godínez et al, 2010;Portela et al, 2016), while the latter transports tropical waters poleward (Willett et al, 2006;Portela et al, 2018). These current systems converge in and around the study area, where they mix and interact with Gulf of California waters intensifying the mesoscale processes in the region (Fiedler and Talley, 2006;Portela et al, 2018). Biologically, this water mass convergence region has been little studied to date, but some authors like Etnoyer et al (2006) have suggested that the contribution of the mesoscale activity to primary productivity could be high, given the high frequency and abundance of top predators in the region.…”

Ommastrephid squid paralarvae potential nursery habitat in the tropical-subtropical convergence off Mexico

“…The paralarvae remain in planktonic phase up to ~ 10 mm ML, when the proboscis splits to form the tentacles (Camarillo-Coop et al , 2013;Zepeda-Benitez et al, 20 14). The plank:tonic life stages, as in all the meroplank:tonic organisms, are the most sensitive to environmental changes and are exposed to higher mortality rates than later ontogenetic stages (Camarillo-Coop et al , 2013;et al , 2010a;Gomez-Valdivia et al , 2015 ;Portela et al , 2018;Sanchez-Velasco et al , 2017. A fourth water mass, with wide thermal range (12 °C < temperature < 32 °C) and high salinity(> 35.1 g kg-1 ) and originating in the Gulf of California, contributes to the interaction and mixing between these three water masses near the entrance of the Gulf.…”

“…1) (Durazo, 2015;Godinez et al , 201 0a;Lavin and Marinone, 2003). During summer and autumn, wind from the southeast drives predominantly poleward flow (Gomez-Valdivia et al , 2015 ;Lavin et al , 2006;Portela et al, 2018). The arrival of tropical surface water in the southern Gulf of California typically deepens the thermocline (Godinez et al , 201 0a;Portela et al , 2016).…”

Larval Fish Habitats and Deoxygenation in the Northern Limit of the Oxygen Minimum Zone off Mexico

“…In the transition zone the surface temperatures oscillate between 18 and 30 °C, and surface salinity varies from 35.1 to 34 g/kg during spring and autumn, respectively (Fiedler & Talley, ). In spring and winter, the intrusion of the tropical branch of the California Current (Kurczyn et al, ) ventilates the hypoxic subsurface waters, while during summer and autumn the influence of the Mexican Coastal Current (Lavín et al, ; Portela et al, ) transport hypoxic and suboxic waters from the tropical domain to the transition zone, rising the hypoxic waters in the area (Márquez‐Artavia et al, ).…”