According to the team of scientists working on this survey, the mysterious freshwater aquifer appears to be the largest of this type on Earth, as it measures from the coast of MA to New Jersey, while extending out 50 miles to the edge of the continental shelf.
The aquifer, a layer of water-bearing porous sediments, generally begins about 600 feet below the ocean floor and bottoms out at about 1,200 feet.
To sum up, thanks to this discovery, new aquifers can be found in other places of the world and could be a great source of water in areas with danger of running out.
However, for discovering it, innovative measurement of electromagnetic waves has been used for mapping the water. Another procedure was to use an apparatus behind the ship, helping them to emit artificial electromagnetic pulses for recording responses from the sub-seafloor.
"If we consider the potential northeast and southwest extensions beyond our profiles, there may be several times more groundwater underlying the northeast portion of the US Atlantic continental shelf, representing a freshwater resource that rivals the largest onshore aquifers", the authors explain. This preserved pockets of "fossil water" in the seabed, and until now it was the standard explanation for any freshwater aquifer found under the ocean. So how did all this fresh water get there? This is the more traditional hypothesis as to how freshwater bodies can form beneath the ocean.
The researchers suggest the freshwater made it under the seabed in two possible ways: either by being drawn to the ocean floor by tides, or by being trapped in scattered pockets under the US continental shelf as glaciers melted approximately 15,000 years ago. Large pockets of fresh water from the melted glaciers then got stuck in these sediment traps.
The water may have been trapped there thousands of years ago as oceans rose after the last glacial age, but researchers also believe the aquifer may now be fed by modern underground runoff from the land. Near the ocean, though, groundwater in coastal sediments may be pumped toward the sea by the rising and falling pressure of tides overhead, explains study co-author and Columbia geophysicist Kerry Key, who compares the process to soaking up water through the sides of a sponge by pressing up and down on it.
The research team out of Columbia University said the aquifer spans at least 350 kilometres from MA to New Jersey and holds an estimated 2.79 trillion litres worth of water, making it the largest such discovery in the world. For comparison, the typical salinity of seawater is 35 ppt. That was done over ten days between New Jersey and MA.
Some of this water might already be useable, but saltier water from the outer aquifer would probably need to be desalinated for most uses, the researchers note. This might still be a valuable discovery, though, both for what it can tell us about the way coastal environments work and how it might help us deal with water scarcity in the future. In coastal areas, there is plenty of undrinkable saltwater, while desalination is costly.