Electromagnetic analysis of the US East Coast seabed has found what researchers believe to be a massive freshwater aquifer spanning at least 350 kilometers (217 miles), according to a study published in Scientific Reports.
Such aquifers are common around the world and are formed during ancient glacial processes dating back to the Ice Age. Researchers were first clued into the aquifer in the 1970s when oil companies sometimes hit fresh water during exploratory drilling. It wasn’t until 2015, however, when scientists conducted measurements of it off southern New Jersey and Martha’s Vineyard, an island in Massachusetts.
“We knew there was fresh water down there in isolated places, but we did not know the extent or geometry,” said lead author Chloe Gustafson in a statement. “It could turn out to be an important resource in other parts of the world.”
Receivers were dropped to the seafloor while a device was towed behind the ship that emitted electromagnetic pulses. Reactions in the seafloor were captured by the receivers, enabling scientists to determine what sort of fluid rests below the seabed because salt water is a better conductor of electromagnetic waves.
Compiling data to measure conductivity below the seafloor, the researchers’ mapping indicates that the deposits of freshwater are largely continuous, starting at the shoreline and extending out to the shallow continental shelf sometimes as far out as 120 kilometers (75 miles), stretching to Rhode Island, Connecticut and New York. Freshwater supplies mostly begin around 183 meters (600 feet) below the ocean floor, but sometimes extend to as far as 3,660 meters (12,000 feet). The scientists estimate the water volume equates to a lake of over 40,000 square kilometers (15,000 square miles).
It’s believed that low-salinity groundwater is abundant around the world, but the science is out on how much exists and how it is distributed around the world because there is not enough data to characterize global aquifers. However, future mapping and a better understanding of their characteristics can be used to improve understanding and models of “past glacial, tectonic, and geomorphic processes.”
But how did it get there in the first place? In their paper, the study authors write that one theory suggests water locked in ice during the last glacial age 15,000 and 20,000 years ago eventually melted. As ice melts, sediments form river deltas on top of the continental shelf, trapping fresh water. As sea levels rose over the following millennia, it would have trapped groundwater in these areas. Additionally, researchers believe the aquifer is fed by runoff from terrestrial water systems and rainfall.
The authors note that future analyses of global deep-sea aquifers may help inform water policies for arid regions currently in danger of running out.