![]() ![]() “Rob’s work is transformational,” Person said. ![]() Repurposing the CSEM technique for freshwater detection could be a significant step forward in the search for offshore fresh water, said Mark Person. Using the technique, Evans was able to find signals of a layer of fresh water off the New Jersey coast in 2015-“at similar depths to where fresh water was originally discovered through drilling,” he said. Since fresh water is a poor conductor of electrical currents, CSEM can distinguish it from salt water and other types of fluids. The electromagnetic fields diffuse down into the seafloor, becoming stronger or weaker depending on the conductivity of the material they are passing through. Transmitters towed by a ship send electromagnetic signals into the ocean. They adapted a technology called Controlled Source Electromagnetic (CSEM) sensing, which traditionally has been used by the oil industry to detect the presence of oil and gas in offshore locations.Ĭonceptually, the process is straightforward. So Evans, in collaboration with Kerry Key, a geophysicist at Scripps Institution of Oceanography, added a complementary technique to help characterize the fluids. When it eventually melted, the ice sheet would have left deposits of fresh water trapped in pockets and pores below the shelf, which later became the seafloor.īut the seismic data can’t tell you much about the types of fluids captured within these geological structures. The erosion, the scientists say, may have been caused by a long-gone ice sheet that poked its way onto the shelf. These involve quietly pulsing acoustic waves through the ocean and into the seafloor to map out geological structures. In 2009, Lizarralde and colleagues from the United States Geological Survey (USGS) began investigating erosion of the continental shelf off Martha’s Vineyard by using seismic surveys. Pools of subsea fresh water and brackish water (fresh water mixed with salt) have shown up thousands of miles from New England in places such as Tanzania and Indonesia, and as nearby as New Jersey, where an artesian freshwater spring sprang out of a borehole 60 miles offshore during scientific drilling in the 1970s.īut only in recent years have scientists begun to focus on New England. But if they are connected to terrestrial aquifers, they could represent renewable sources of fresh water.” A focus on New England “If they are isolated deposits of fossil glacial fresh water, they’d be gone once tapped. “I’d argue that these freshwater reserves ultimately could be tapped and be a resource,” Evans said. That drilling proposal has been led by Mark Person, a hydrologist at New Mexico Institute of Mining and Technology, and Brandon Dugan at the Colorado School of Mines. The glaciers melted, and the fresh water was subsequently trapped beneath the seafloor when sea levels rose.Įvans and Lizarralde have been anxiously awaiting the go-ahead on a proposal to drill water samples hundreds of feet below the shelf off Martha’s Vineyard to prove that subsea freshwater deposits are there and to determine their sources. Another theory suggests the fresh water came from glaciers during ice ages, when sea level was lower and the continental shelf was exposed dry land. How did the water get there? One theory, the scientists say, is that fresh water may be percolating all the way down through the shelf from aquifers on land. These subsea reservoirs could someday be tapped like vast offshore wells to provide additional freshwater resources to an increasingly water-scarce planet, say Rob Evans and Dan Lizarralde, scientists at Woods Hole Oceanographic Institution.Įvans and Lizarralde have been investigating what they think may be big pockets of fresh water sitting right off Martha’s Vineyard in New England, under the shallow continental shelf before the seafloor plunges steeply into the abyss. By some estimates, nearly 120,000 cubic miles of fresh water lies buried beneath the seafloor-more water than the sun evaporates from the Earth’s surface each year. And they’re finding it in places many people wouldn’t expect: under the ocean. And in California, devastating drought conditions in recent years idled nearly a half-million acres of crops and triggered the loss of tens of thousands of jobs.Īs areas of the planet dry up, scientists are hunting for new sources of fresh water. In Brazil, residents of the water-starved city of São Paulo have been frenetically digging homemade wells to mine fresh water, while schoolkids skip brushing their teeth as a conservation measure. In the African Sahel, generations of severe droughts have claimed millions of lives and have turned fertile pastures into swaths of desert. In some places, water is dangerously scarce.
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