A reevaluation of submarine groundwater discharge along the southeastern coast of North America

New data of fluxes of radium isotopes and concentrations of radium in coastal groundwater enable an estimation of fluxes of submarine groundwater discharge (SGD) to a large section of the South Atlantic Bight (SAB). The new fluxes are considerably greater than SGD fluxes to this region estimated earlier. The annual average total SGD fluxes, which represent a range of salinity, are 3 times greater than the river fluxes. The highest fluxes of radium and SGD occur in the summer off the coast of Georgia. When scaled per kilometer of shoreline, the SGD flux is the same for the coastlines of Onslow Bay, NC (140 km), a section of the South Atlantic Bight from Onslow Bay, NC, to Cresent Beach, Florida, United States (600 km), and the entire Atlantic Ocean (75,000 km). The fact that each independent estimate is based on different methods and assumptions gives confidence to the results. These SGD fluxes are not restricted to the shoreline but occur throughout the continental shelf. They are important for supplying not only radium but also nutrients, carbon, metals, and freshwater to these coastal waters.