Abstract

The Mexican Tropical Pacific (MTP) is a key component of the Eastern Tropical North Pacific Oxygen Minimum Zone, yet its carbonate system variability remains poorly constrained. This study examines wind-driven circulation effects on dissolved oxygen (DO) and the carbonate system -dissolved inorganic carbon (DIC), total alkalinity (TA), total-scale pH (pHT), partial pressure of CO2 in seawater (pCO2w) and air-sea CO2 fluxes (FCO2)- in the Gulf of Tehuantepec (GT) and Tehuantepec Bowl (TB). Hydrographic data and discrete water samples were collected at 50 oceanographic stations during March 2020. Principal Component Analysis (PCA) identifies wind-driven circulation as the primary control of biogeochemical variability. Tehuano wind events and mesoscale eddies promoted upwelling of low-oxygen (DO < 20 & micro;mol kg(-1)) and high-DIC (>2200 & micro;mol kg(-1)) waters to 50 m depth in the central GT, while downwelling conditions prevailed in the TB. Stoichiometric analysis revealed DIC-DO coupling (slope = -1.39). Overall, the MTP acted as CO2 source (FCO2 ranging from -1.92 to 24.11 mmol m(-2) d(-1)), with enhanced emissions linked to eddy-induced upwelling. This study provides the first integrated characterization of the carbonate system across both the GT and TB.