Scientists recently discovered vast freshwater reservoirs beneath the Atlantic seafloor, stretching off the U.S. East Coast from the states of New Jersey to Maine.
The find was “a beautiful scientific accident,” Brandon Dugan, a professor of geophysics at the Colorado School of Mines, U.S., and co-chief scientist on the expedition, told Mongabay in a video call.
Dugan said his curiosity about freshwater beneath the ocean floor was piqued in the 1990s while doing a literature review for his Ph.D. research. “I found these interesting papers that said, ‘Hey, when we’re out looking for oil and gas, we didn’t find oil and gas, but we found water where water shouldn’t be.’”
Around the same time, other researchers found freshwater at unexpected depths on the East Coast island of Nantucket. So, Dugan and colleagues used computer models to simulate how far freshwater might extend beneath the ocean floor.
Earlier this year, Dugan joined more than 40 researchers from a dozen countries for a two-and-a-half-month expedition off the U.S. East Coast. Drilling at three distances from the shore, they found freshwater at each site. Seawater has a salinity close to 35 parts per thousand (ppt), or 35 grams per liter of water, but freshwater at the site nearest the shore at 30 kilometers (20 miles) had salinity of less than 1 ppt. Salinity increased with distance from the shore but remained much lower than that of seawater.
The team is analyzing the chemistry of the water samples to determine their origin and age, but preliminary results suggest it’s the result of a glacier from some 20,000 years ago.
At that time, massive glaciers extended from the mainland to islands including Nantucket, Dugan said. The enormous weight of the ice could have forced freshwater into the ground and then pushed it offshore beneath the ocean, where it’s been trapped ever since, he added.
However, researchers have also found freshwater off the coasts of South Africa and Florida where there’s not been relatively recent glacial activity. In such places, the local landscape and soil type likely allow freshwater to more easily move from land to seabed, Dugan said.
“There’s anecdotal evidence of fresh and groundwater existing off the coast of every continent. Some are very big, like New England. Some are small, like Florida,” he added.
However, tapping that water would be expensive and logistically challenging, Dugan said, adding the capability to do that is at least a decade away.
Dugan also cautioned that offshore freshwater is a finite resource that won’t recharge like groundwater, and that drawing it poses concerns for sensitive seafloor ecosystems and the potential to trigger small earthquakes if water is pumped out too quickly.
The question, he said, is “how can I have this backup supply of water in a time of need? Not, how do I expand in a time when water stresses are already growing?”
Banner image: Residual fluid gushes from the core drilling rig. Image by AP Photo/Carolyn Kaster.
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