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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Daily images of ice cover in the Arctic Ocean (left) and around Antarctica reveal sea ice formation and melting at the poles over the course of two years (Sept 14, 2023 to Sept. 13, 2025).Trent Schindler/NASA’s Scientific Visualization Studio With the end of summer approaching in the Northern Hemisphere, the extent of sea ice in the Arctic shrank to its annual minimum on Sept. 10, according to NASA and the National Snow and Ice Data Center. The total sea ice coverage was tied with 2008 for the 10th-lowest on record at 1.78 million square miles (4.60 million square kilometers). In the Southern Hemisphere, where winter is ending, Antarctic ice is still accumulating but remains relatively low compared to ice levels recorded before 2016.
The areas of ice covering the oceans at the poles fluctuate through the seasons. Ice accumulates as seawater freezes during colder months and melts away during the warmer months. But the ice never quite disappears entirely at the poles. In the Arctic Ocean, the area the ice covers typically reaches its yearly minimum in September. Since scientists at NASA and the National Oceanic and Atmospheric Administration (NOAA) began tracking sea ice at the poles in 1978, sea ice extent has generally been declining as global temperatures have risen.
“While this year’s Arctic sea ice area did not set a record low, it’s consistent with the downward trend,” said Nathan Kurtz, chief of the Cryospheric Sciences Laboratory at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Arctic ice reached its lowest recorded extent in 2012. Ice scientist Walt Meier of the National Snow and Ice Data Center at the University of Colorado, Boulder, attributes that record low to a combination of a warming atmosphere and unusual weather patterns. This year, the annual decline in ice initially resembled the changes in 2012. Although the melting tapered off in early August, it wasn’t enough to change the year-over-year downward trend. “For the past 19 years, the minimum ice coverage in the Arctic Ocean has fallen below the levels prior to 2007,” Meier said. “That continues in 2025.”
Antarctic sea ice nearing annual maximum
As ice in the Arctic reaches its annual minimum, sea ice around the Antarctic is approaching its annual maximum. Until recently, ice in the ocean around the Southern pole has been more resilient than sea ice in the North, with maximum coverage increasing slightly in the years before 2015. “This year looks lower than average,” Kurtz said. “But the Antarctic system as a whole is more complicated,” which makes predicting and understanding sea ice trends in the Antarctic more difficult.
It’s not yet clear whether lower ice coverage in the Antarctic will persist, Meier said. “For now, we’re keeping an eye on it” to see if the lower sea ice levels around the South Pole are here to stay or only part of a passing phase.
A history of tracking global ice
For nearly five decades, NASA and NOAA have relied on a variety of satellites to build a continuous sea ice record, beginning with the NASA Nimbus-7 satellite (1978–1987) and continuing with the Special Sensor Microwave/Imager and the Special Sensor Microwave Imager Sounder on Defense Meteorological Satellite Program satellites that began in 1987. The Advanced Microwave Scanning Radiometer–for EOS on NASA’s Aqua satellite also contributed data from 2002 to 2011. Scientists have extended data collection with the 2012 launch of the Advanced Microwave Scanning Radiometer 2 aboard a JAXA (Japan Aerospace Exploration Agency) satellite.
With the launch of ICESat-2 in 2018, NASA has added the continuous observation of ice thickness to its recording. The ICESat-2 satellite measures ice height by recording the time it takes for laser light from the satellite to reflect from the surface and travel back to detectors on board.
“We’ve hit 47 years of continuous monitoring of the global sea ice extent from satellites,” said Angela Bliss, assistant chief of NASA’s Cryospheric Sciences Laboratory. “This data record is one of the longest, most consistent satellite data records in existence, where every single day we have a look at the sea ice in the Arctic and the Antarctic.”
By James Riordon
NASA Goddard Space Flight Center
Media contact: Elizabeth Vlock
NASA Headquarters
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Last Updated Sep 17, 2025 LocationNASA Goddard Space Flight Center Related Terms
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By NASA
5 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
A ship plows through rough seas in the Bering Sea in the aftermath of Typhoon Tip, one of the largest hurricanes on record. The Sentinel-6B satellite will provide data crucial to forecasting sea states, information that can help ships avoid danger. CC BY 2.0 NOAA/Commander Richard Behn Sea surface height data from the Sentinel-6B satellite, led by NASA and ESA, will help with the development of marine weather forecasts, alerting ships to possible dangers.
Because most global trade travels by ship, accurate, timely ocean forecasts are essential. These forecasts provide crucial information about storms, high winds, and rough water, and they depend on measurements provided by instruments in the ocean and by satellites including Sentinel-6B, a joint mission led by NASA and ESA (European Space Agency) that will provide essential sea level and other ocean data after it launches this November.
The satellite will eventually take over from its twin, Sentinel-6 Michael Freilich, which launched in 2020. Both satellites have an altimeter instrument that measures sea levels, wind speeds, and wave heights, among other characteristics, which meteorologists feed into models that produce marine weather forecasts. Those forecasts provide information on the state of the ocean as well as the changing locations of large currents like the Gulf Stream. Dangerous conditions can result when waves interact with such currents, putting ships at risk.
“Building on NASA’s long legacy of satellite altimetry data and its real-world impact on shipping operations, Sentinel-6B will soon take on the vital task of improving ocean and weather forecasts to help keep ships, their crews, and cargo safe”, said Nadya Vinogradova Shiffer, lead program scientist at NASA Headquarters in Washington.
Sentinel-6 Michael Freilich and Sentinel-6B are part of the Sentinel-6/Jason-CS (Continuity of Service) mission, the latest in a series of ocean-observing radar altimetry missions that have monitored Earth’s changing seas since the early 1990s. Sentinel-6/Jason-CS is a collaboration between NASA, ESA, the European Union, EUMETSAT (European Organisation for the Exploitation of Meteorological Satellites), and NOAA (U.S. National Oceanic and Atmospheric Administration). The European Commission provided funding support, and the French space agency CNES (Centre National d’Études Spatiales) contributed technical support.
Keeping current
“The ocean is getting busier, but it’s also getting more dangerous,” said Avichal Mehra, deputy director of the Ocean Prediction Center at the National Weather Service in College Park, Maryland. He and his colleagues produce marine weather forecasts using data from ocean-based instruments as well as complementary measurements from five satellites, including Sentinel-6 Michael Freilich. Among those measurements: sea level, wave height, and wind speed. The forecasters derive the location of large currents from changes in sea level.
One of the planet’s major currents, the Gulf Stream is located off the southeastern coast of the United States, but its exact position varies. “Ships will actually change course depending on where the Gulf Stream is and the direction of the waves,” said Mehra. “There have been instances where, in calm conditions, waves interacting with the Gulf Stream have caused damage or the loss of cargo containers on ships.”
Large, warm currents like the Gulf Stream can have relatively sharp boundaries since they are generally higher than their surroundings. Water expands as it warms, so warm seawater is taller than cooler water. If waves interact with these currents in a certain way, seas can become extremely rough, presenting a hazard to even the largest ships.
“Satellite altimeters are the only reliable measurement we have of where these big currents can be,” said Deirdre Byrne, sea surface height team lead at NOAA in College Park.
There are hundreds of floating sensors scattered about the ocean that could pick up parts of where such currents are located, but these instruments are widely dispersed and limited in the area they measure at any one time. Satellites like Sentinel-6B offer greater spatial coverage, measuring areas that aren’t regularly monitored and providing essential information for the forecasts that ships need.
Consistency is key
Sentinel-6B won’t just help marine weather forecasts through its near-real-time data, though. It will also extend a long-term dataset featuring more than 30 years of sea level measurements, just as Sentinel-6 Michael Freilich does today.
“Since 1992, we have launched a series of satellites that have provided consistent sea level observations from the same orbit in space. This continuity allows each new mission to be calibrated against its predecessors, providing measurements with centimeter-level accuracy that don’t drift over time,” said Severine Fournier, Sentinel-6B deputy project scientist at NASA’s Jet Propulsion Laboratory in Southern California.
This long-running, repeated measurement has turned this dataset into the gold standard sea level measurement from space — a reference against which data from other sea level satellites is checked. It also serves as a baseline, giving forecasters a way to tell what ocean conditions have looked like over time and how they are changing now. “This kind of data can’t be easily replaced,” said Mehra.
More about Sentinel-6B
Sentinel-6/Jason-CS was jointly developed by ESA, EUMETSAT, NASA, and NOAA, with funding support from the European Commission and technical support from CNES.
A division of Caltech in Pasadena, JPL contributed three science instruments for each Sentinel-6 satellite: the Advanced Microwave Radiometer, the Global Navigation Satellite System – Radio Occultation, and the Laser Retroreflector Array. NASA is also contributing launch services, ground systems supporting operation of the NASA science instruments, the science data processors for two of these instruments, and support for the U.S. members of the international Ocean Surface Topography and Sentinel-6 science teams.
For more about Sentinel-6/Jason-CS, visit:
https://sealevel.jpl.nasa.gov/missions/jason-cs-sentinel-6
News Media Contacts
Jane J. Lee / Andrew Wang
Jet Propulsion Laboratory, Pasadena, Calif.
626-491-1943 / 626-379-6874
jane.j.lee@jpl.nasa.gov / andrew.wang@jpl.nasa.gov
2025-116
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Last Updated Sep 11, 2025 Related Terms
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By NASA
NASA/Rachel Tilling Sea ice is frozen seawater that floats in the ocean. This photo, taken from NASA’s Gulfstream V Research Aircraft on July 21, 2022, shows Arctic sea ice in the Lincoln Sea north of Greenland.
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Text and image credit: NASA/Rachel Tilling
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By European Space Agency
The next sea-level monitoring satellite, Copernicus Sentinel-6B, has begun its journey from Europe to the Vandenberg Space Force Base in California, where it is scheduled to launch in November. Carefully packed into a climate-controlled container, the satellite is currently crossing the Atlantic Ocean aboard the cargo ship Industrial Dolphin.
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By Space Force
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