Researchers have for the first time mapped a freshwater aquifer under the ocean, suggesting it and other similar systems could be a new source of water.
- The newly-mapped aquifer is located off the East Coast, stretching from near Martha's Vineyard to the waters off Long Island and New Jersey.
The big picture: Millions of people face greater water stress from population growth, groundwater depletion and climate change. While the water described in the study, published in Scientific Reports, would need to be desalinized before consumption, it would not require the energy-intensive process currently undertaken in some countries, such as Israel.
What they did: The researchers used new electromagnetic methods typically employed for mapping offshore oil and gas resources.
- They deployed receivers to the seafloor to measure the electromagnetic fields below, and also towed a device that emitted electromagnetic pulses and recorded the seafloor's responses to them.
- Because saltwater is a better conductor of electromagnetic waves compared to freshwater, the aquifer showed up as a clear band of low conductance.
What they found: an aquifer system located within porous rock formations extending from the shoreline to about 50 miles off the coast of both survey locations.
- The researchers note it may extend well beyond the study region, and the aquifer could be one that "rivals the largest onshore aquifers."
- The aquifer isn't a trapped underground lake that can simply be tapped into like a straw, says lead author Chloe Gustafson, also of Columbia University. "It's more like a water-soaked sponge," she says.
- This aquifer spans nearly 220 miles of the Atlantic Coast from end to end, and may hold at least 670 cubic miles of low-salinity groundwater.
The backstory: It's thought the groundwater originated during the end of the last glaciation, some 15,000 to 20,000 years ago, when sea levels were lower and mile-thick ice sheets retreated.
- The glacial runoff formed offshore deltas and eventually trapped pockets of water underneath them.
- In a surprising finding, the researchers say the aquifer is also likely receiving some fresh water from the land via subterranean runoff, which raises the possibility it may be recharged over time.
Between the lines: A 2013 study found freshwater aquifers likely are present in Outer Continental Shelf regions of every continent. That finding combined with the new results could spur more surveys to search for tappable offshore groundwater reserves.
- However, like groundwater on land, this water should be treated more like a savings account that can be quickly depleted.
- Also, because the water lies within porous rocks, the geological consequences of pumping it out would need to be studied.
The bottom line: “The big thing that we want people to know is that this isn’t just an isolated incident off the coast of New Jersey and Martha's Vineyard,” Gustafson says.