A drilling expedition off Nantucket has confirmed a massive freshwater reservoir buried beneath the Atlantic seafloor — stretching from New Jersey to Maine, hypothesized since the 1960s, and holding e

Key Points:

• A 2025 drilling expedition (IODP³-NSF Expedition 501) confirmed the existence of a massive freshwater reservoir beneath the Atlantic seafloor off the northeastern U.S. coast, originally hypothesized based on 1960s-70s oil company drilling reports.
• The reservoir, sealed by an impermeable clay and silt layer, extends from offshore New Jersey to Maine and is large enough to supply a city the size of New York City with freshwater for approximately 800 years.
• The freshwater was emplaced about 20,000 years ago during the last glacial period, likely from glacial meltwater forced into sediments, and is a finite resource not currently replenished by natural processes.
• While the reservoir offers significant potential for regional water security, large-scale extraction would require extensive infrastructure development and environmental impact studies, making it not an immediate solution.
• Similar offshore freshwater reservoirs may exist in other coastal regions worldwide where comparable glacial and geological conditions occurred, prompting future scientific investigations.