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By NASA
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NASA Satellites Reveal Abrupt Drop in Global Freshwater Levels
Earth (ESD) Earth Home Explore Climate Change Science in Action Multimedia Data For Researchers GRACE satellites measure gravity as they orbit the planet to reveal shifting levels of water on the Earth (artist’s concept). NASA/JPL-Caltech An international team of scientists using observations from NASA-German satellites found evidence that Earth’s total amount of freshwater dropped abruptly starting in May 2014 and has remained low ever since. Reporting in Surveys in Geophysics, the researchers suggested the shift could indicate Earth’s continents have entered a persistently drier phase.
From 2015 through 2023, satellite measurements showed that the average amount of freshwater stored on land — that includes liquid surface water like lakes and rivers, plus water in aquifers underground — was 290 cubic miles (1,200 cubic km) lower than the average levels from 2002 through 2014, said Matthew Rodell, one of the study authors and a hydrologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “That’s two and a half times the volume of Lake Erie lost.”
During times of drought, along with the modern expansion of irrigated agriculture, farms and cities must rely more heavily on groundwater, which can lead to a cycle of declining underground water supplies: freshwater supplies become depleted, rain and snow fail to replenish them, and more groundwater is pumped. The reduction in available water puts a strain on farmers and communities, potentially leading to famine, conflicts, poverty, and an increased risk of disease when people turn to contaminated water sources, according to a UN report on water stress published in 2024.
The team of researchers identified this abrupt, global decrease in freshwater using observations from the Gravity Recovery and Climate Experiment (GRACE) satellites, operated by the German Aerospace Center, German Research Centre for Geosciences, and NASA. GRACE satellites measure fluctuations in Earth’s gravity on monthly scales that reveal changes in the mass of water on and under the ground. The original GRACE satellites flew from March 2002 to October 2017. The successor GRACE–Follow On (GRACE–FO) satellites launched in May 2018.
This map shows the years that terrestrial water storage hit a 22-year minimum (i.e., the land was driest) at each location, based on data from the GRACE and GRACE/FO satellites. A significantly large portion of the global land surface reached this minimum in the nine years since 2015, which happen to be the nine warmest years in the modern temperature record. Image by NASA Earth Observatory/Wanmei Liang with data courtesy of Mary Michael O’Neill The decline in global freshwater reported in the study began with a massive drought in northern and central Brazil, and was followed shortly by a series of major droughts in Australasia, South America, North America, Europe, and Africa. Warmer ocean temperatures in the tropical Pacific from late 2014 into 2016, culminating in one of the most significant El Niño events since 1950, led to shifts in atmospheric jet streams that altered weather and rainfall patterns around the world. However, even after El Niño subsided, global freshwater failed to rebound. In fact, Rodell and team report that 13 of the world’s 30 most intense droughts observed by GRACE occurred since January 2015. Rodell and colleagues suspect that global warming might be contributing to the enduring freshwater depletion.
Global warming leads the atmosphere to hold more water vapor, which results in more extreme precipitation, said NASA Goddard meteorologist Michael Bosilovich. While total annual rain and snowfall levels may not change dramatically, long periods between intense precipitation events allow the soil to dry and become more compact. That decreases the amount of water the ground can absorb when it does rain.
“The problem when you have extreme precipitation,” Bosilovich said, “is the water ends up running off,” instead of soaking in and replenishing groundwater stores. Globally, freshwater levels have stayed consistently low since the 2014-2016 El Niño, while more water remains trapped in the atmosphere as water vapor. “Warming temperatures increase both the evaporation of water from the surface to the atmosphere, and the water-holding capacity of the atmosphere, increasing the frequency and intensity of drought conditions,” he noted.
While there are reasons to suspect that the abrupt drop in freshwater is largely due to global warming, it can be difficult to definitively link the two, said Susanna Werth, a hydrologist and remote sensing scientist at Virginia Tech, who was not affiliated with the study. “There are uncertainties in climate predictions,” Werth said. “Measurements and models always come with errors.”
It remains to be seen whether global freshwater will rebound to pre-2015 values, hold steady, or resume its decline. Considering that the nine warmest years in the modern temperature record coincided with the abrupt freshwater decline, Rodell said, “We don’t think this is a coincidence, and it could be a harbinger of what’s to come.”
By James R. Riordon
NASA’s Earth Science News Team
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Last Updated Nov 15, 2024 Editor James Riordon Contact James Riordon james.r.riordon@nasa.gov Location NASA Goddard Space Flight Center Related Terms
Earth Goddard Space Flight Center GRACE (Gravity Recovery And Climate Experiment) GRACE-FO (Gravity Recovery and Climate Experiment Follow-on) Water on Earth Explore More
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By European Space Agency
Torrential rainfall causing deadly flash floods has hit southern and eastern Spain in regions including the Costa del Sol, where the city of Malaga is located, and Valencia in the east. As these areas struggle to cope with the aftermath, satellite technology has played a crucial role in assessing the damages of the affected areas.
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By NASA
Mars: Perseverance (Mars 2020) Perseverance Home Mission Overview Rover Components Mars Rock Samples Where is Perseverance? Ingenuity Mars Helicopter Mission Updates Science Overview Objectives Instruments Highlights Exploration Goals News and Features Multimedia Perseverance Raw Images Images Videos Audio More Resources Mars Missions Mars Sample Return Mars Perseverance Rover Mars Curiosity Rover MAVEN Mars Reconnaissance Orbiter Mars Odyssey More Mars Missions The Solar System The Sun Mercury Venus Earth The Moon Mars Jupiter Saturn Uranus Neptune Pluto & Dwarf Planets Asteroids, Comets & Meteors The Kuiper Belt The Oort Cloud 2 min read
Just Keep Roving
Image from Perseverance’s Right Navigation Camera, looking back towards rover tracks from past drives, into Jezero crater. The camera is located high on the rover mast, and here the rover is looking back in the direction of the Jezero crater floor. This image was acquired on October 4th, 2024 (Sol 1288) at the local mean solar time of 12:51:26. NASA/JPL-Caltech Throughout the past week, Perseverancehas continued marching up the Jezero crater rim. This steep ascent through the Martian regolith (soil) can prove to be slow driving for the rover, as the wheels can slip on the steepest areas. This is like trying to run up a hill of sand on a beach – with every step forward, you also slip back a little way down the hill! This just means the Science and Engineering teams work together closely to plan slow and steady drives through this tricky terrain.
Driving through the Mount Ranier quadrangle, the team identified a relatively obstacle-free path to reach the crater rim which they designated Summerland Trail, aptly named from a very popular hiking trail that ascends Mount Ranier. Perseverance is trekking to the next waypoint near an outcrop of rocks called Pico Turquino, where the science team hopes to perform its next proximity science investigations with its instruments PIXL and back-online SHERLOC.
While roving along Summerland Trail, Perseverance is constantly observing the surrounding terrain. SuperCam and Mastcam-Z have been observing rocks on the ground and on a distant hill, called Crystal Creek. In addition, during this time Perseverance can put its eyes to the sky to make observations of the sun and atmosphere. Last week, the Mastcam-Z camera captured images of Phobos (one of Mars’ two moons) transiting in front of the sun!
This image, showing Phobos transiting in front of the sun, was acquired using Perseverance’s Left Mastcam-Z camera. Acquired on September 30th, 2024 (Sol 1285) at the local mean solar time of 11:10:04. NASA/JPL-Caltech/ASU While the Mars2020 team is itching to reach the ancient stratigraphy exposed in the crater rim, for now, the focus is on documenting our surroundings while navigating the ascent.
Written by Eleanor Moreland, Ph.D. Student Collaborator at Rice University
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Rover Tracks Image: Mars Perseverance Sol 1288: Right Navigation Camera (Navcam) Quadrangles: NASA’s Perseverance Mars Rover Mission Honors Navajo Language Hiking Trail: Summerland Trailhead (U.S. National Park Services) SHERLOC: Perseverance Matters – NASA Science Mars Moons – NASA Science Phobos Transit Image: Mars Perseverance Sol 1285 – Left Mastcam-Z Camera Crater Rim: Reaching New Heights to Unravel Deep Martian History! Share
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Last Updated Oct 17, 2024 Related Terms
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