Daniel PrattPreliminary analyses suggest the reservoir, which sits beneath the seafloor and appears to stretch from offshore New Jersey as far north as Maine, was locked in place under frigid conditions around 20,000 years ago, hinting that it formed in the last glacial period due, partly, to thick ice sheets. https://www.livescience.com/planet-earth/rivers-oceans/enormous-freshwater-reservoir-discovered-off-the-east-coast-may-be-20-000-years-old-and-big-enough-to-supply-nyc-for-800-years
Enormous freshwater reservoir discovered off the East Coast may be 20,000 years old and big enough to supply NYC for 800 years
An expedition off the coast of Massachusetts has confirmed the existence of a freshwater reservoir beneath the seafloor. Now, scientists are starting to understand when and how it formed.