In a shocking discovery, scientists have done a new survey of the sub-seafloor off the U.S. Northeast coast and identified a gigantic aquifer of relatively fresh water trapped in porous sediments lying below the salty ocean. The discovery seems to be the most massive of such formation yet found in the world. From Massachusetts to New Jersey, the aquifer stretches from the shore and extends more or less continuously out about 50 miles to the edge of the continental shelf. According to the research, such aquifers probably lie off many other coasts worldwide and could provide desperately needed water for arid areas that are now in danger of running out.
For the scientists to map the water, they employed innovative measurements of electromagnetic waves which remained invisible to other technologies. In the words of a Ph.D., a candidate at Columbia University's Lamont-Doherty Earth Observatory, Chloe Gustafson, the lead author of the study which appears in the journal Scientific Reports, they knew there was fresh water down there in isolated places, but they did not know the extent or geometry. It could turn out to be an essential resource in other parts of the world.
The researchers noted that the water probably got under the seabed in one of two different ways. Towards the end of the last glacial age, about 15,000 to 20,000 years ago, much of the world's water was locked up in mile-deep ice; in North America, it extended through what is now northern New Jersey, Long Island, and the New England coast. Sea levels were much lower, exposing much of what is now the underwater U.S. continental shelf. With the melting of the ice, sediments formed enormous river deltas on top of the shelf, and fresh water got trapped there in scattered pockets. Later, sea levels rose. Till present, the trapping of such "fossil" water has been the regular explanation for any freshwater found under the ocean.
However, the team explained that the recent discoveries indicate that the aquifer is also being fed by modern subterranean runoff from the land. As water from rainfall and water bodies percolates through onshore sediments, it is likely pumped seaward by the rising and falling pressure of tides. Not only that, the aquifer is generally freshest near the shore, and saltier the farther out, suggesting that it mixes gradually with ocean water over time. Ordinarily, terrestrial freshwater contains less than 1 part per thousand salts, and this is about the value found undersea near land.
