A massive underground reservoir of freshwater lies off the East Coast, potentially supplying a city the size of New York City for 800 years. Researchers believe it formed around 20,000 years ago during the last ice age when glaciers covered the area.
This reservoir stretches beneath the ocean floor from New Jersey to Maine. It was spotted during a recent research expedition that followed up on old findings from the 1960s and 1970s. Brandon Dugan, co-chief scientist of the expedition and a geophysics professor, described the project as a “lifelong dream.”
The three-month journey, known as Expedition 501, collected about 13,200 gallons of water from sites near Nantucket and Martha’s Vineyard. Early results suggest the reservoir may be even larger than initially thought.
Scientists have long known about fresh water in this region, first reported by the U.S. Geological Survey (USGS) more than 60 years ago. Initial findings hinted at freshwater trapped in sediments under the sea. Dugan noted that theories emerged in the 1980s but then faded into obscurity.
In 2003, Dugan and Mark Person, a hydrology professor, rediscovered these records and proposed three main ways this freshwater could have accumulated beneath the ocean. First, during low sea levels, rainfall could seep underground. Secondly, rainwater might flow from mountains into the seabed. Lastly, as ice sheets expanded and prompted sea levels to drop, meltwater could be trapped under sediment layers.
Recent analyses indicate that most of the freshwater likely originated from glaciers during the last ice age, which lasted from 2.6 million to 11,700 years ago. While tall mountains aren’t present along the East Coast, there could be rainfall from icy fronts, suggesting a mix of sources.
During the expedition, researchers drilled down 1,300 feet below the seafloor, capturing layers of freshwater beneath salty sediment, which was sealed off by clay and silt. This barrier helps to keep the two types of water separate, although it might not have been strong enough to prevent glacial meltwater from infiltrating the freshwater layer.
Salinity measurements revealed that as researchers moved farther from shore, the water’s freshness decreased. The closest site registered a salt level safe for drinking at just 1 part per 1,000, whereas farther out, salinity rose to 4 to 5 parts per 1,000, and up to 18 parts per 1,000 at the farthest point.
The team is now delving deeper into their findings, studying various elements like microbes and sediments. This could provide clarity about the reservoir’s size and formation timeline. Dugan mentioned that results should be ready soon, aiming to create a knowledge base for any future usage of this hidden resource.
The discovery hints at a significant freshwater source that could be crucial in the face of climate change and rising sea levels. As freshwater scarcity becomes a growing concern worldwide, understanding this reservoir may inform future decisions on water management.
For more on freshwater studies, visit the U.S. Geological Survey.
