River-dominated continental shelves significantly influence coastal carbon cycling and ocean acidification due to substantial freshwater river discharge. Despite this importance, the contributions of riverine dissolved inorganic carbon (DIC), total alkalinity (TA), and nutrient loads to surface pCO2 trends remain inadequately quantified. This study employs the Regional Ocean Modelling System (ROMS) to evaluate the effects of riverine DIC, TA, and nutrient fluxes on surface pCO2 trends in the northern Gulf of Mexico/America from 2001 to 2019. A control simulation (CTR) representing historical river inputs was compared to three scenarios: no historical riverine DIC and TA flux (NRC), no historical nutrient flux (NRN), and high freshwater discharge (60% of historical levels, HRD60). Results indicated positive pCO2 trends in most nGoM regions, except for HRD60, which exhibited some negative trends. First-order Taylor series decomposition revealed that DIC is the primary contributor to increasing pCO2 trends, accounting for 50%, while TA offsets this by 31%. Sea surface temperature (SST) contributes 13%, and sea surface salinity (SSS) contributes 6%. Under the HRD60 simulation, increased freshwater discharge enhances both DIC and TA delivery, leading to spatially heterogeneous yet dampened pCO2 trends due to stronger buffering. These findings emphasize that coastal pCO2 trajectories depend on the magnitude and composition of riverine fluxes. Carbonate supplies account for 59% of total river-driven modulation of surface pCO2, with biological uptake offsetting the remaining 41%. Future climate projections must consider these nonlinear interactions to effectively assess acidification risks in river-influenced coastal regions.
Adeagbo O. S., Ou Y., Xue Z. G., Holstein D., Gravinese P. M., Zhang L. & Craft H., 2025. Detangling the elevated sea-surface pCO2 trend in a river-dominated continental shelf using a high-resolution regional ocean model. ESS Open Archive. Article.
