Offshore freshened groundwater within the continental shelf offshore New England, USA

Sediments beneath the ocean, within 62 miles (100 km) of the U.S. shoreline, contain large volumes of low-salinity groundwater similar to freshwater. This project aims to study its origin, salinity changes, and biological responses by monitoring water properties at two locations south of Martha’s Vineyard, MA. Sensors for pressure, temperature, and electrical resistivity will be installed in boreholes drilled during an international ocean drilling expedition. Data will be used to refine groundwater models. Public engagement includes a podcast series and educational activities, while the project also trains a graduate student in groundwater science and engineering design. Scientific ocean drilling and hydrological modeling suggest that 1 million cubic kilometers of offshore freshened groundwater (OFG) may exist in continental shelf aquifers worldwide. However, key uncertainties remain about its emplacement, recharge, discharge, and role in nutrient cycling. This project aims to constrain the hydrogeologic flow system by installing Simple Cabled Instrument for Measuring Parameters In-situ (SCIMPI) systems at NSF/IODP3 Expedition 501 Sites MV-08A and MV-03C offshore Martha’s Vineyard, MA. These sensors will provide continuous data on fluid pressure, temperature, and resistivity to refine groundwater models and improve understanding of OFG dynamics. Additionally, a podcast docuseries will engage the public in marine and freshwater science, incorporating educational activities for K-12 and undergraduate students. A graduate student will gain hands-on experience in engineering, groundwater science, and science communication. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.