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Glacier melt intensifying freshwater loss and accelerating sea-level rise
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By European Space Agency
Image: These summer images from the Copernicus Sentinel-2 and Sentinel-1 missions showcase different satellite views of Greenland’s west coast. View the full article
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By NASA
The Artemis II Orion spacecraft is lifted from the Final Assembly and Testing (FAST) Cell and placed in the west altitude chamber inside the Operations and Checkout Building at NASA’S Kennedy Space Center in Florida on June 28, 2024. Inside the altitude chamber, the spacecraft underwent a series of tests simulating deep space vacuum conditions.Photo Credit: NASA / Rad Sinyak After extensive analysis and testing, NASA has identified the technical cause of unexpected char loss across the Artemis I Orion spacecraft’s heat shield.
Engineers determined as Orion was returning from its uncrewed mission around the Moon, gases generated inside the heat shield’s ablative outer material called Avcoat were not able to vent and dissipate as expected. This allowed pressure to build up and cracking to occur, causing some charred material to break off in several locations.
“Our early Artemis flights are a test campaign, and the Artemis I test flight gave us an opportunity to check out our systems in the deep space environment before adding crew on future missions,” said Amit Kshatriya, deputy associate administrator, Moon to Mars Program Office, NASA Headquarters in Washington. “The heat shield investigation helped ensure we fully understand the cause and nature of the issue, as well as the risk we are asking our crews to take when they venture to the Moon.”
Findings
Teams took a methodical approach to understanding and identifying the root cause of the char loss issue, including detailed sampling of the Artemis I heat shield, review of imagery and data from sensors on the spacecraft, and comprehensive ground testing and analysis.
During Artemis I, engineers used the skip guidance entry technique to return Orion to Earth. This technique provides more flexibility by extending the range Orion can fly after the point of reentry to a landing spot in the Pacific Ocean. Using this maneuver, Orion dipped into the upper part of Earth’s atmosphere and used atmospheric drag to slow down. Orion then used the aerodynamic lift of the capsule to skip back out of the atmosphere, then reenter for final descent under parachutes to splashdown.
Using Avcoat material response data from Artemis I, the investigation team was able to replicate the Artemis I entry trajectory environment — a key part of understanding the cause of the issue — inside the arc jet facilities at NASA’s Ames Research Center in California. They observed that during the period between dips into the atmosphere, heating rates decreased, and thermal energy accumulated inside the heat shield’s Avcoat material. This led to the accumulation of gases that are part of the expected ablation process. Because the Avcoat did not have “permeability,” internal pressure built up, and led to cracking and uneven shedding of the outer layer.
After NASA’s Orion spacecraft was recovered at the conclusion of the Artemis I test flight and transported to NASA’s Kennedy Space Center in Florida, its heat shield was removed from the crew module inside the Operations and Checkout Building and rotated for inspection. Credit: NASA Teams performed extensive ground testing to replicate the skip phenomenon before Artemis I. However, they tested at much higher heating rates than the spacecraft experienced in flight. The high heating rates tested on the ground allowed the permeable char to form and ablate as expected, releasing the gas pressure. The less severe heating seen during the actual Artemis I reentry slowed down the process of char formation, while still creating gases in the char layer. Gas pressure built up to the point of cracking the Avcoat and releasing parts of the charred layer. Recent enhancements to the arc jet facility have enabled a more accurate reproduction of the Artemis I measured flight environments, so that this cracking behavior could be demonstrated in ground testing.
While Artemis I was uncrewed, flight data showed that had crew been aboard, they would have been safe. The temperature data from the crew module systems inside the cabin were also well within limits and holding steady in the mid-70s Fahrenheit. Thermal performance of the heat shield exceeded expectations.
Engineers understand both the material phenomenon and the environment the materials interact with during entry. By changing the material or the environment, they can predict how the spacecraft will respond. NASA teams unanimously agreed the agency can develop acceptable flight rationale that will keep crew safe using the current Artemis II heat shield with operational changes to entry.
NASA’s Investigation Process
Soon after NASA engineers discovered the condition on the Artemis I heat shield, the agency began an extensive investigation process, which included a multi-disciplinary team of experts in thermal protection systems, aerothermodynamics, thermal testing and analysis, stress analysis, material test and analysis, and many other related technical areas. NASA’s Engineering and Safety Center was also engaged to provide technical expertise including nondestructive evaluation, thermal and structural analysis, fault tree analysis, and other testing support.
“We took our heat shield investigation process extremely seriously with crew safety as the driving force behind the investigation,” said Howard Hu, manager, Orion Program, NASA’s Johnson Space Center in Houston. “The process was extensive. We gave the team the time needed to investigate every possible cause, and they worked tirelessly to ensure we understood the phenomenon and the necessary steps to mitigate this issue for future missions.”
The Artemis I heat shield was heavily instrumented for flight with pressure sensors, strain gauges, and thermocouples at varying ablative material depths. Data from these instruments augmented analysis of physical samples, allowing the team to validate computer models, create environmental reconstructions, provide internal temperature profiles, and give insight into the timing of the char loss.
Approximately 200 Avcoat samples were removed from the Artemis I heat shield at NASA’s Marshall Space Flight Center in Alabama for analysis and inspection. The team performed non-destructive evaluation to “see” inside the heat shield.
One of the most important findings from examining these samples was that local areas of permeable Avcoat, which had been identified prior to the flight, did not experience cracking or char loss. Since these areas were permeable at the start of the entry, the gases produced by ablation were able to adequately vent, eliminating the pressure build up, cracking, and char loss.
A test block of Avcoat undergoes heat pulse testing inside an arc jet test chamber at NASA’s Ames Research Center in California. The test article, configured with both permeable (upper) and non-permeable (lower) Avcoat sections for comparison, helped to confirm understanding of the root cause of the loss of charred Avcoat material that engineers saw on the Orion spacecraft after the Artemis I test flight beyond the Moon.Credit: NASA
Engineers performed eight separate post-flight thermal test campaigns to support the root cause analysis, completing 121 individual tests. These tests took place in facilities with unique capabilities across the country, including the Aerodynamic Heating Facility at the Arc-Jet Complex at Ames to test convective heating profiles with various test gases; the Laser Hardened Materials Evaluation Laboratory at Wright‐Patterson Air Force Base in Ohio to test radiative heating profiles and provide real-time radiography; as well as the Interaction Heating Facility at Ames to test combined convective and radiative heating profiles in the air at full-block scale.
Aerothermal experts also completed two hypersonic wind tunnel test campaigns at NASA’s Langley Research Center in Virginia and CUBRC aerodynamic test facilities in Buffalo, New York, to test a variety of char loss configurations and enhance and validate analytical models. Permeability testing was also performed at Kratos in Alabama, the University of Kentucky, and Ames to help further characterize the Avcoat’s elemental volume and porosity. The Advanced Light Source test facility, a U.S. Department of Energy scientific user facility at Lawrence Berkeley National Laboratory, was also used by engineers to examine the heating behavior of the Avcoat at a microstructure level.
In the spring of 2024, NASA stood up an independent review team to conduct an extensive review of the agency’s investigation process, findings, and results. The independent review was led by Paul Hill, a former NASA leader who served as the lead space shuttle flight director for Return to Flight after the Columbia accident, led NASA’s Mission Operations Directorate, and is a current member of the agency’s Aerospace Safety Advisory Panel. The review occurred over a three-month period to assess the heat shield’s post-flight condition, entry environment data, ablator thermal response, and NASA’s investigation progress. The review team agreed with NASA’s findings on the technical cause of the physical behavior of the heat shield.
Heat Shield Advancements
Knowing that permeability of Avcoat is a key parameter to avoid or minimize char loss, NASA has the right information to assure crew safety and improve performance of future Artemis heat shields. Throughout its history, NASA has learned from each of its flights and incorporated improvements into hardware and operations. The data gathered throughout the Artemis I test flight has provided engineers with invaluable information to inform future designs and refinements. Lunar return flight performance data and a robust ground test qualification program improved after the Artemis I flight experience are supporting production enhancements for Orion’s heat shield. Future heat shields for Orion’s return from Artemis lunar landing missions are being produced to achieve uniformity and consistent permeability. The qualification program is currently being completed along with the production of more permeable Avcoat blocks at NASA’s Michoud Assembly Facility in New Orleans.
For more information about NASA’s Artemis campaign, visit:
https://www.nasa.gov/artemis
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By European Space Agency
As Arctic temperatures rise, marine-terminating glaciers—especially in places like Svalbard—are undergoing rapid retreat and intensified calving.
The ESA-funded Space for Shore project utilises radar data from the Copernicus Sentinel-1 mission to provide precise, year-over-year insights into glacier retreat and calving intensity, particularly in areas like Kongsfjorden, where notable glaciers are experiencing significant retreat.
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By NASA
4 min read
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
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Preparations for Next Moonwalk Simulations Underway (and Underwater)
Coastal locations, such as Drakes Bay on the Point Reyes peninsula in Northern California, are increasingly vulnerable to sea level rise.NOAA/NMFS/WCR/CCO The information will help people who live in coastal areas prepare for impacts caused by rising sea levels.
Earth’s ocean is rising, disrupting livelihoods and infrastructure in coastal communities around the world. Agencies and organizations are working to prepare people as their world changes around them, and NASA information is helping these efforts.
The agency’s global data is now available in the sea level section of the Earth Information Center. NASA developed the global sea level change website in collaboration with the U.S. Department of Defense, the World Bank, the U.S. Department of State, and the United Nations Development Programme.
The site includes information on projected sea level rise through the year 2150 for coastlines around the world, as well as estimates of how much flooding a coastal community or region can expect to see in the next 30 years. The projections come from data collected by NASA and its partners and from computer models of ice sheets and the ocean, as well as the latest sea level assessment from the Intergovernmental Panel on Climate Change, and other sources.
“NASA innovates for the benefit of humanity. Our cutting-edge instruments and data-driven information tools help communities and organizations respond to natural hazards and extreme weather, and inform critical coastal infrastructure planning decisions,” said Karen St. Germain, director of the Earth science division at NASA Headquarters in Washington.
Information to Action
International organizations such as the World Bank will use the data from the global sea level change site for tasks including the creation of Climate Risk Profiles for countries especially vulnerable to sea level rise.
The Defense Department will continue to incorporate sea level rise data into its plans to anticipate and respond to hazards posed to its facilities by the effects of rising oceans. Similarly, the State Department uses the information for activities ranging from disaster preparedness to long-term adaptation planning to supporting partners around the world in related efforts.
“We are at a moment of truth in our fight against the climate crisis. The science is unequivocal and must serve as the bedrock upon which decision-making is built. With many communities around the world already facing severe impacts from sea-level rise, this new resource provides a vital tool to help them protect lives and livelihoods. It also illustrates what is at stake between a 1.5-degree-Celsius world and a current-policies trajectory for all coastal communities worldwide,” said Assistant Secretary-General Selwin Hart, special adviser to the United Nations secretary-general on climate action and just transition.
Rising Faster
NASA-led data analyses have revealed that between 1970 and 2023, 96% of countries with coastlines have experienced sea level rise. The rate of that global rise has also accelerated, more than doubling from 0.08 inches (0.21 centimeters) per year in 1993 to about 0.18 inches (0.45 centimeters) per year in 2023.
As the rate of sea level rise increases, millions of people could face the related effects sooner than previously projected, including larger storm surges, more saltwater intrusion into groundwater, and additional high-tide flood days — also known as nuisance floods or sunny day floods.
“This new platform shows the timing of future floods and the magnitude of rising waters in all coastal countries worldwide, connecting science and physics to impacts on people’s livelihoods and safety,” said Nadya Vinogradova Shiffer, director of the ocean physics program at NASA Headquarters in Washington.
Data released earlier this year found that Pacific Island nations will experience at least 6 inches (15 centimeters) of sea level rise in the next 30 years. The number of high-tide flood days will increase by an order of magnitude for nearly all Pacific Island nations by the 2050s.
“The data is clear: Sea levels are rising around the world, and they’re rising faster and faster,” said Ben Hamlington, a sea level researcher at NASA’s Jet Propulsion Laboratory in Southern California and head of the agency’s sea level change science team. “Having the best information to make decisions about how to plan for rising seas is more crucial than ever.”
To explore the global sea level change site:
https://earth.gov/sealevel
News Media Contacts
Karen Fox / Elizabeth Vlock
NASA Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / elizabeth.a.vlock@nasa.gov
Jane J. Lee / Andrew Wang
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0307 / 626-379-6874
jane.j.lee@jpl.nasa.gov / andrew.wang@jpl.nasa.gov
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Last Updated Nov 13, 2024 Related Terms
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