Okay, we already know that there are water-bearing minerals within the Earth’s mantle that are essentially deconstructed water. But this time when we say there are giant reservoirs of water hiding deep under the ocean? We mean fresh water, as you and I would recognize it. That we could drink. Like, water-water. About 2,800 cubic kilometers of it. Just to emphasize how freaking big that is, that’s enough to fill over a billion Olympic swimming pools. Or to put another way: it stretches not only the length of New Jersey’s coastline, but also that of Massachusetts, Rhode Island, Connecticut, and most of New York. Casual. Oceanographic teams have known for a while that there are pockets of fresh water below the seafloor — they would run into them occasionally when drilling offshore for oil. But when geologists and geophysicists started to explore how big these pockets actually are? They were floored. A collaborative team from Columbia University and Woods Hole Oceanographic Institution used two different marine electromagnetic methods to pulse the seafloor. One method involved deploying ten broadband electromagnetic receivers onto the actual seafloor, which then ‘looked’ down to detect what lurks below. The second method was to tow an antennae broadcasting a certain frequency behind a ship, with electromagnetic receivers at four different depth levels. These techniques rely on the fact that salt water is a much better conductor of electromagnetic waves than fresh water is, allowing us to probe things that we can’t see visually, like the composition of the Earth below the seafloor. Scientists believe the water’s probably been there for a pretty long time. When everything was frozen in the last Ice Age, the sea levels were lower, so what is now this ocean floor was actually exposed, and when the glaciers melted, freshwater melt-off formed watersheds on the exposed ocean floor sediments, eventually getting trapped there in huge pockets as sea levels rose again. The water’s origin story may mean that aquifers like this could provide us with clues about the glaciers and sea levels of the past. But the team also believes that these undersea aquifers are being supplied with new freshwater from subterranean systems. Rising and falling ocean tides provide alternating pressure to deep onshore sediments, acting a bit like an absorbent sponge, pulling underground water toward the ocean. This means that the hydrologic systems under the land, many of which we already use, may be connected to undersea aquifers in ways we didn’t previously know about. Researchers hope that this discovery means this particular aquifer is not the only one of its kind, and that they can use similar methods to find more. And at this point you may be wondering: can we actually use this water? The UN estimates there will be 9.7 billion people living on Earth by 2050, and several countries, like India, are already suffering major water shortages. As early as 2025, about half of the world’s population may lack as much fresh water as they need, and maybe these newly discovered undersea aquifers could provide us with an unexpected solution. But if we ever wanted to use this water for drinking, we would have to desalinate it, as it does get a little salty — especially the farther out into the aquifer you go. It is much less salty than ocean water, though, making it less expensive and difficult to desalinate — and potentially giving us some hope when staring down an impending water crisis. There’s cause for pause also, because new simulations have shown that because of the connection between onshore hydrologic systems and undersea aquifers, pulling water from under the ocean may then pull more water from under the land, and could cause the ground to literally sink. So before we can think of these surprisingly massive aquifers as usable resources, a lot of thought — and probably a lot of computer modeling — is going to need to be put into how we could access them and if we do, what the effects will be. Are there other deep-Earth projects that would like us to cover? Let us know in the comments. And for more exciting discoveries, make sure to tune into Shark Week, to dive into a whole week of shark content, starting July 28th on Discovery. As always, thanks for watching, and we’ll see you next time.