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Honolulu is pictured here beside a calm sea in 2017. A JPL technology recently detected and confirmed a tsunami up to 45 minutes prior to detection by tide gauges in Hawaii, and it estimated the speed of the wave to be over 580 miles per hour (260 meters per second) near the coast.NASA/JPL-Caltech A massive earthquake and subsequent tsunami off Russia in late July tested an experimental detection system that had deployed a critical component just the day before.
A recent tsunami triggered by a magnitude 8.8 earthquake off Russia’s Kamchatka Peninsula sent pressure waves to the upper layer of the atmosphere, NASA scientists have reported. While the tsunami did not wreak widespread damage, it was an early test for a detection system being developed at the agency’s Jet Propulsion Laboratory in Southern California.
Called GUARDIAN (GNSS Upper Atmospheric Real-time Disaster Information and Alert Network), the experimental technology “functioned to its full extent,” said Camille Martire, one of its developers at JPL. The system flagged distortions in the atmosphere and issued notifications to subscribed subject matter experts in as little as 20 minutes after the quake. It confirmed signs of the approaching tsunami about 30 to 40 minutes before waves made landfall in Hawaii and sites across the Pacific on July 29 (local time).
“Those extra minutes of knowing something is coming could make a real difference when it comes to warning communities in the path,” said JPL scientist Siddharth Krishnamoorthy.
Near-real-time outputs from GUARDIAN must be interpreted by experts trained to identify the signs of tsunamis. But already it’s one of the fastest monitoring tools of its kind: Within about 10 minutes of receiving data, it can produce a snapshot of a tsunami’s rumble reaching the upper atmosphere.
The dots in this graph indicate wave disturbances in the ionosphere as measured be-tween ground stations and navigation satellites. The initial spike shows the acoustic wave coming from the epicenter of the July 29 quake that caused the tsunami; the red squiggle shows the gravity wave the tsunami generated.NASA/JPL-Caltech The goal of GUARDIAN is to augment existing early warning systems. A key question after a major undersea earthquake is whether a tsunami was generated. Today, forecasters use seismic data as a proxy to predict if and where a tsunami could occur, and they rely on sea-based instruments to confirm that a tsunami is passing by. Deep-ocean pressure sensors remain the gold standard when it comes to sizing up waves, but they are expensive and sparse in locations.
“NASA’s GUARDIAN can help fill the gaps,” said Christopher Moore, director of the National Oceanic and Atmospheric Administration Center for Tsunami Research. “It provides one more piece of information, one more valuable data point, that can help us determine, yes, we need to make the call to evacuate.”
Moore noted that GUARDIAN adds a unique perspective: It’s able to sense sea surface motion from high above Earth, globally and in near-real-time.
Bill Fry, chair of the United Nations technical working group responsible for tsunami early warning in the Pacific, said GUARDIAN is part of a technological “paradigm shift.” By directly observing ocean dynamics from space, “GUARDIAN is absolutely something that we in the early warning community are looking for to help underpin next generation forecasting.”
How GUARDIAN works
GUARDIAN takes advantage of tsunami physics. During a tsunami, many square miles of the ocean surface can rise and fall nearly in unison. This displaces a significant amount of air above it, sending low-frequency sound and gravity waves speeding upwards toward space. The waves interact with the charged particles of the upper atmosphere — the ionosphere — where they slightly distort the radio signals coming down to scientific ground stations of GPS and other positioning and timing satellites. These satellites are known collectively as the Global Navigation Satellite System (GNSS).
While GNSS processing methods on Earth correct for such distortions, GUARDIAN uses them as clues.
SWOT Satellite Measures Pacific Tsunami The software scours a trove of data transmitted to more than 350 continuously operating GNSS ground stations around the world. It can potentially identify evidence of a tsunami up to about 745 miles (1,200 kilometers) from a given station. In ideal situations, vulnerable coastal communities near a GNSS station could know when a tsunami was heading their way and authorities would have as much as 1 hour and 20 minutes to evacuate the low-lying areas, thereby saving countless lives and property.
Key to this effort is the network of GNSS stations around the world supported by NASA’s Space Geodesy Project and Global GNSS Network, as well as JPL’s Global Differential GPS network that transmits the data in real time.
The Kamchatka event offered a timely case study for GUARDIAN. A day before the quake off Russia’s northeast coast, the team had deployed two new elements that were years in the making: an artificial intelligence to mine signals of interest and an accompanying prototype messaging system.
Both were put to the test when one of the strongest earthquakes ever recorded spawned a tsunami traveling hundreds of miles per hour across the Pacific Ocean. Having been trained to spot the kinds of atmospheric distortions caused by a tsunami, GUARDIAN flagged the signals for human review and notified subscribed subject matter experts.
Notably, tsunamis are most often caused by large undersea earthquakes, but not always. Volcanic eruptions, underwater landslides, and certain weather conditions in some geographic locations can all produce dangerous waves. An advantage of GUARDIAN is that it doesn’t require information on what caused a tsunami; rather, it can detect that one was generated and then can alert the authorities to help minimize the loss of life and property.
While there’s no silver bullet to stop a tsunami from making landfall, “GUARDIAN has real potential to help by providing open access to this data,” said Adrienne Moseley, co-director of the Joint Australian Tsunami Warning Centre. “Tsunamis don’t respect national boundaries. We need to be able to share data around the whole region to be able to make assessments about the threat for all exposed coastlines.”
To learn more about GUARDIAN, visit:
https://guardian.jpl.nasa.gov
News Media Contacts
Jane J. Lee / Andrew Wang
Jet Propulsion Laboratory, Pasadena, Calif.
626-379-6874 / 818-354-0307
jane.j.lee@jpl.nasa.gov / andrew.wang@jpl.nasa.gov
Written by Sally Younger
2025-117
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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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