Understanding upper water mass dynamics in the Gulf of Mexico by linking physical and biogeochemical features

In the Gulf of Mexico (GoM), upper 300 m water column contains a mixture types derived from masses North Atlantic and Caribbean Sea, namely Surface Water (CSW), Subtropical Underwater (SUW), Common (GCW), Tropical Central (TACW). These are mainly altered by mesoscale processes local evaporation, which modulate biogeochemical cycles. this study, we improve our understanding mass dynamics including data when evaluating T-S relationship to define water-mass boundaries, particularly observed thermohaline characteristics overlap. The variables considered were apparent oxygen utilization (AOU), nitrate, dissolved inorganic carbon (DIC). obtained eight cruises carried out in central southern regions GoM an additional cruise that covered entire coastal-ocean region. new proposed boundaries instrumental clarifying surface waters. Of note, GCW on western side is not formed mixing CSW SUW but remnant with TACW. winter, mixed GCW, composition waters was affected, as increase nitrate DIC concentrations positive AOU values. detected at during summer negative values, low almost undetectable concentrations. presence or absence modulated depth nitracline likely influenced primary productivity.