MAPPING SUBMARINE GROUNDWATER DISCHARGE USING A THERMAL INFRARED SENSOR MOUNTED ON AN UNMANNED AERIAL SYSTEM IN COASTAL NORTH CAROLINA, USA

Submarine groundwater discharge (SGD), the direct discharge of groundwater from coastal aquifers to the ocean, is an important fresh water and dissolved nutrient source in Onslow Bay, NC. Hence, mapping SGD hotspots and hot moments is important to better understand their impacts to coastal waters. Here we applied innovative geospatial analysis techniques using thermal infrared (TIR) data from a multispectral satellite and a senseFly eBee equipped with multiple sensors to map SGD anomalies, with high accuracy over a vast areal extent. In-situ radon, temperature, salinity, and global positioning coordinates were measured during the survey for data validation. Relative to commonly used chemical tracing techniques, utilizing geospatial analysis of TIR and multispectral data enables a more cost-efficient, spatially-accurate, and time-efficient method for monitoring SGD. Survey results from Masonboro Barrier Island revealed cooler sea surface temperature anomalies adjacent to the wider section of the barrier island where more groundwater can potentially accumulate and discharge along the island shoreline. High ²²²Rn concentrations in seawater adjacent to this site confirms the presence of SGD. The average groundwater discharge within a tidal cycle at this site is 0.78 m d^-1. This approach demonstrates the utility of UAS-TIR systems in mapping SGD hotspots and potentially hot moments in coastal areas such as barrier islands.