The deposit, which contains brackish water, could be a source of easily desalinated drinking water
The Atlantic Ocean is not the first place one would think of looking for fresh water, but that is exactly where Columbia University Lamont-Doherty Earth Observatory researchers have found it — and not just a little bit. The newly discovered aquifer is embedded in porous sediments beneath a 15,000-square-mile expanse of sea floor that stretches from just off Ocean County, New Jersey, to Martha’s Vineyard, Massachusetts. It is the largest formation of its kind ever discovered, holding an estimated 670 cubic miles of water. It has been theorized that such fossil aquifers were deposited at the end of the last ice age, but testing has shown that the newly discovered aquifer also is being fed by subterranean runoff from inland.
To put it more accurately, the aquifer’s water is mostly brackish. Samples taken near the shore have a salinity of about 1 part per thousand (ppt), which is typical of average terrestrial groundwater. But the salinity climbs the farther from shore the sample is taken. At its outer edges, the aquifer’s salinity increases to 15 ppt (seawater typically has a salinity of 35 ppt).
Brackish water is easier to desalinate than seawater and costs less, making such aquifers a possible new source of potable water. The lead author of the article on the discovery, Columbia University doctoral candidate Chloe Gustafson, said, “It could turn out to be an important resource in other parts of the world.” The discovery was announced in the journal Scientific Reports.
The aquifer’s bordering states of New Jersey, New York, Connecticut, Rhode Island, and Massachusetts currently have no need for such an offshore brackish water resource, but the discovery could have huge implications for other regions desperate for a new water source, including Cape Town, Jakarta, and even California.
Searching for Undersea Aquifers
Gustafson and co-author Kerry Key, a geophysicist, already knew there was water under the seafloor because in the past oil drillers sometimes hit fresh water. But, no one knew the extent of the deposits. Key, who had already developed electromagnetic, sub-seafloor imaging technology for oil exploration, recently had the idea to adapt the technology to search for water.
Key and Rob L. Evans of Woods Hole Oceanographic Institution tested the technology in 2015 with seafloor receivers and an electromagnetic pulse emitter towed behind the Lamont-Doherty research ship Marcus G. Langseth. Salt water is a better electromagnetic wave conductor than fresh, so the two exploration methods simply identified fresh water as a band of low conductance.
The testing was able to show that these were not scattered deposits of fresh water, but one huge aquifer starting at the shore and extending out as far as 75 miles to the edge of the continental shelf, at depths of 600-1,200 feet below the sea floor.