Predicted Episode of Submarine Groundwater Discharge Onto the South Carolina, USA, Continental Shelf and Its Effect on Dissolved Oxygen

Submarine groundwater discharge (SGD) may directly influence the dissolved oxygen (DO) content of coastal bottom waters. Here, we report a predicted episode of enhanced SGD that caused low DO concentrations on the South Carolina continental shelf. The prediction model linked episodes of SGD to upwelling-favorable winds. The data revealed these waters were a factor of 2-6 higher in Ra-226 and Ra-228 compared to typical bottom water values and were significantly depleted in DO (<130 mu M). The tight Ra-228:Ra-226 correlation of these data was similar to values during a strong hypoxic event off SC in 2012. Water ages from Ra-224 and Ra-223 indicated the event occurred 2-9 days before sampling. The success of the prediction lends added credence to the correlation of upwelling-favorable winds-but not necessarily accompanied by upwelling-to episodic SGD events. This prediction from wind data represents a major advance for quantifying SGD in the region.

Automated summary

This study reveals that submarine groundwater discharge (SGD) can directly affect the dissolved oxygen (DO) content in coastal bottom waters. The researchers developed a prediction model that linked episodes of enhanced SGD to upwelling-favorable winds. The data showed that these water masses had higher Ra-226 and Ra-228 values compared to typical bottom water, and were significantly depleted in DO. The successful prediction using wind data represents a major advancement in quantifying SGD in the region.