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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Watersheds on the U.S. Eastern Seaboard will be among the areas most affected by underground saltwater intrusion by the year 2100 due to sea level rise and changes in groundwater supplies, according to a NASA-DOD study. NASA’s Terra satellite captured this image on April 21, 2023. Intrusion of saltwater into coastal groundwater can make water there unusable, damage ecosystems, and corrode infrastructure.
Seawater will infiltrate underground freshwater supplies in about three of every four coastal areas around the world by the year 2100, according to a recent study led by researchers at NASA’s Jet Propulsion Laboratory in Southern California. In addition to making water in some coastal aquifers undrinkable and unusable for irrigation, these changes can harm ecosystems and corrode infrastructure.
Called saltwater intrusion, the phenomenon happens below coastlines, where two masses of water naturally hold each other at bay. Rainfall on land replenishes, or recharges, fresh water in coastal aquifers (underground rock and soil that hold water), which tends to flow below ground toward the ocean. Meanwhile, seawater, backed by the pressure of the ocean, tends to push inland. Although there’s some mixing in the transition zone where the two meet, the balance of opposing forces typically keeps the water fresh on one side and salty on the other.
Now, two impacts of climate change are tipping the scales in favor of salt water. Spurred by planetary warming, sea level rise is causing coastlines to migrate inland and increasing the force pushing salt water landward. At the same time, slower groundwater recharge — due to less rainfall and warmer weather patterns — is weakening the force moving the underground fresh water in some areas.
Worldwide Intrusion
Saltwater intrusion will affect groundwater in about three of every four coastal aquifers around the world by the year 2100, a NASA-DOD study estimates. Saltwater can make groundwater in coastal areas undrinkable and useless for irrigation, as well as harm ecosystems and corrode infrastructure.NASA/JPL-Caltech The study, published in Geophysical Research Letters in November, evaluated more than 60,000 coastal watersheds (land area that channels and drains all the rainfall and snowmelt from a region into a common outlet) around the world, mapping how diminished groundwater recharge and sea level rise will each contribute to saltwater intrusion while estimating what their net effect will be.
Considering the two factors separately, the study’s authors found that by 2100 rising sea levels alone will tend to drive saltwater inland in 82% of coastal watersheds studied. The transition zone in those places would move a relatively modest distance: no more than 656 feet (200 meters) from current positions. Vulnerable areas include low-lying regions such as Southeast Asia, the coast around the Gulf of Mexico, and much of the United States’ Eastern Seaboard.
Meanwhile, slower recharge on its own will tend to cause saltwater intrusion in 45% of the coastal watersheds studied. In these areas, the transition zone would move farther inland than it will from sea level rise — as much as three-quarters of a mile (about 1,200 meters) in some places. The regions to be most affected include the Arabian Peninsula, Western Australia, and Mexico’s Baja California peninsula. In about 42% of coastal watersheds, groundwater recharge will increase, tending to push the transition zone toward the ocean and in some areas overcoming the effect of saltwater intrusion by sea level rise.
All told, due to the combined effects of changes in sea level and groundwater recharge, saltwater intrusion will occur by century’s end in 77% of the coastal watersheds evaluated, according to the study.
Generally, lower rates of groundwater recharge are going to drive how far saltwater intrudes inland, while sea level rise will determine how widespread it is around the world. “Depending on where you are and which one dominates, your management implications might change,” said Kyra Adams, a groundwater scientist at JPL and the paper’s lead author.
For example, if low recharge is the main reason intrusion is happening in one area, officials there might address it by protecting groundwater resources, she said. On the other hand, if the greater concern is that sea level rise will oversaturate an aquifer, officials might divert groundwater.
Global Consistency
Co-funded by NASA and the U.S. Department of Defense (DOD), the study is part of an effort to evaluate how sea level rise will affect the department’s coastal facilities and other infrastructure. It used information on watersheds collected in HydroSHEDS, a database managed by the World Wildlife Fund that uses elevation observations from the NASA Shuttle Radar Topography Mission. To estimate saltwater intrusion distances by 2100, the researchers used a model accounting for groundwater recharge, water table rise, fresh- and saltwater densities, and coastal migration from sea level rise, among other variables.
Study coauthor Ben Hamlington, a climate scientist at JPL and a coleader of NASA’s Sea Level Change Team, said that the global picture is analogous to what researchers see with coastal flooding: “As sea levels rise, there’s an increased risk of flooding everywhere. With saltwater intrusion, we’re seeing that sea level rise is raising the baseline risk for changes in groundwater recharge to become a serious factor.”
A globally consistent framework that captures localized climate impacts is crucial for countries that don’t have the expertise to generate one on their own, he added.
“Those that have the fewest resources are the ones most affected by sea level rise and climate change,” Hamlington said, “so this kind of approach can go a long way.”
News Media Contacts
Andrew Wang / Jane J. Lee
Jet Propulsion Laboratory, Pasadena, Calif.
626-379-6874 / 818-354-0307
andrew.wang@jpl.nasa.gov / jane.j.lee@jpl.nasa.gov
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Last Updated Dec 11, 2024 Related Terms
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By USH
Kenneth Arnold was a business owner and experienced private pilot, who often traveled to meetings around the Pacific Northwest in his small CallAir A-2. He was a well-respected founder of the Idaho Search and Rescue Pilots Association, and had built up 9,000 flying hours by the time he departed Chehalis, Washington, on a routine 150-mile flight to Yakima on the afternoon of 24 June 1947.
Arnold had deviated from his intended flight path in the hope of locating a Marine Corps C-46 transport plane that had crashed near Mount Rainier and claiming the $5,000 reward. Having failed to spot the wreckage, he made a 300-degree turn 9,200 feet above the town of Mineral and witnessed a bright flash in the distance. Looking north, Arnold reported seeing a formation of nine roughly circular objects flying at an incredible speed. He subsequently calculated that they were moving at more than 1,700 miles per hour.
Arnold was most startled by the lack of a tail on the objects, but initially just assumed that he had witnessed an experimental military aircraft. He reported the sighting to the general manager of the airfield at Yakima when he landed, and before long the story had spread.
The fact that Arnold was both a respected businessman and experienced pilot meant that his account was taken seriously by the press. Consequently he began to be bombarded with requests for interviews. When questioned about the objects, he repeatedly likened their flying-style to how a pie plate or saucer might skip across water. In what he later complained was an ‘historic misquote’, the press coined the phrase ‘flying saucers’ to describe what he had seen.
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By HubbleSite
Appearances can be deceiving. In this NASA Hubble Space Telescope image, an odd celestial duo, the spiral galaxy NGC 4319 [center] and a quasar called Markarian 205 [upper right], appear to be neighbors. In reality, the two objects don't even live in the same city. They are separated by time and space. NGC 4319 is 80 million light-years from Earth. Markarian 205 (Mrk 205) is more than 14 times farther away, residing 1 billion light-years from Earth. The apparent close alignment of Mrk 205 and NGC 4319 is simply a matter of chance.
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