In the South Atlantic Bight (SAB), changes in the strength and proximity to the coast of the Gulf Stream are thought to be primary factors determining the shelf-break upwelling rate. However, it is still not clear if and to what extent those factors influence cross-shelf nutrient fluxes and shape the ocean biogeochemistry at interannual and longer timescales. Here, we use a high-resolution regional ocean-biogeochemical model, an ocean reanalysis product, and a satellite-derived chlorophyll dataset to investigate the interannual ocean-biogeochemical variability in the SAB during 1993-2022. Regional model outputs suggest that year-to-year changes in phytoplankton production are indeed largely driven by upwelling of cold and nutrient-rich water to the shelf-break. The upwelling variability, reflected in bottom temperature and vertically integrated production patterns, is strongly linked to surface velocity changes in the Gulf Stream near the shelf break, but weakly related to the depth-integrated Gulf Stream transport. The Gulf Stream’s velocity changes, and the temperature and production anomalies, are well correlated to the alongshore wind stress, suggesting that local wind is the leading driver of the shelf-break upwelling variability. Those relationships are also supported by circulation patterns from ocean reanalysis and satellite chlorophyll anomalies. Finally, we examine the simulated carbonate system changes linked to the slope-shelf interchanges, finding that shelf-break upwelling significantly increases bottom acidification, a pattern linked to the low carbonate concentration in the slope waters. Our study thus provides new insight to better constrain the impacts of the Gulf Stream and local wind on the SAB biogeochemical variability.
Gomez F. A., Ross A., Lee S. K., Volkov D. L., Kim D., John J. G. & Stock C. A., 2025. Wind control of the interannual ocean-biogeochemical variability in the South Atlantic Bight. ESS Open Archive. Article.
