A Shallow Drilling Campaign to Assess the Pleistocene Hydrogeology, Geomicrobiology, Nutrient Fluxes, and Fresh Water Resources of the Atlantic Continental Shelf, New England

Fresh groundwater within New England Atlantic continental shelf sediments extends 100 km offshore. However, this onshore-offshore freshwater system has not been studied to assess freshwater emplacement mechanisms, freshwater residence time, and how long-term climate conditions and meteoric recharge have influenced these systems. This project will drill submarine wells in the offshore portion of the onshore-offshore freshwater system on the Atlantic continental shelf south of Martha’s Vineyard, MA, USA to study sediment cores. Understanding emplacement mechanisms of freshwater lenses offshore New England will also lead to a better fundamental understanding of this worldwide hydrogeological phenomenon and its impact on biogeochemical cycling. The project will maintain dedicated outreach activities to inform the local population about the research outcomes and will include an outreach officer, speaking at community events, visiting classrooms, and speaking with the media. Groundwater within New England Atlantic continental shelf sediments in Plio-Pleistocene aquifers is fresh (salinity <1000 mg/l) and water with salinity <3000 mg/l extends 100 km offshore. The impact of these dynamic freshwater systems on microbial processes and rates, and fluxes of carbon, nitrogen, other nutrients, and rare-earth elements to the ocean are also unknown. This project will study the dynamics of the offshore portion of the onshore-offshore freshwater system on the Atlantic continental shelf south of Martha’s Vineyard, MA, USA by characterizing the sediments, fluids, and microbes at three drill sites on NSF-IODP3 Expedition 501. The campaign will help to constrain and quantify the (1) spatial distribution of subseafloor freshwater and overall porewater geochemistry, (2) emplacement mechanisms of this freshened groundwater, (3) microbe diversity and activity, and (4) anomalous pressure distribution. Understanding emplacement mechanisms of freshwater lenses offshore New England will also lead to a better fundamental understanding of this worldwide hydrogeological phenomenon and its impact on biogeochemical cycling. All data will be provided through an open-access repository for the broader science community. 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.