Biogeochemical Response to Mesoscale Eddies and Tehuano Wind Events in the Oxygen Minimum Zone off the Gulf of Tehuantepec

Abstract In the oxygen minimum zone of the eastern tropical North Pacific off the Gulf of Tehuantepec, mesoscale eddies and offshore jets often develop in response to Tehuano wind events. These dynamic features play crucial roles in modulating the vertical distribution of nutrients, dissolved oxygen, biogeochemical cycling, and regional primary productivity. This study analyzed data from two BGC‐Argo floats deployed from 2022 to 2023 that followed distinct northward and southward trajectories while collecting data on a wide range of oceanographic conditions. The floats sampled anticyclonic and cyclonic eddies, a shear zone, and Tehuano wind events. The results indicate that the base of the oxycline coincided with the upper boundary of Subtropical Subsurface Water. Anticyclonic eddies deepened the oxycline, creating oxygen‐rich and nitrate‐poor conditions within the upper 100–200 m of the water column. In contrast, cyclonic eddies, the shear zone, and Tehuano wind events shoaled the base of the oxycline to 25–50 m, enhancing hypoxia, increasing nitrate availability in surface waters, and elevating chlorophyll‐a concentrations. Notably, some eddies sampled by the southern float exhibited elevated nitrate concentrations between 200 and 400 m, suggesting a seasonal intrusion of oxygenated equatorial waters that may have inhibited nitrogen loss. Overall, these findings highlight the intricate links between physical forcing, biogeochemical structures, and microbial activity in this region.