Latest news with #SurfaceWaterOceanTopography
Yahoo
2 days ago
- Science
- Yahoo
For 9 Days, Earth Was Sending Out Mysterious Signals. Now We Know What They Were.
"Hearst Magazines and Yahoo may earn commission or revenue on some items through these links." Here's what you'll learn when you read this story: Strange signals coming from the Arctic in 2023 were assumed to be a seiche (trapped water with waves sloshing back and forth), but this was never confirmed. Previous instruments used to measure seismic weather phenomena were not able to pick up enough information, but NASA's SWOT satellite eventually found that the signal actually was from a seiche caused by a landslide. Reconstructions of what the weather was like during the days SWOT picked up the signal also show that it couldn't have been anything but a seiche. As fascinating as bizarre signals from other planets can be—teaching us about earthquakes on Mars or auroras in the skies of Jupiter—sometimes even weirder signals come from weather extremes happening right here on Earth. For nine days in 2023, an unknown seismic pulse was generated by the Earth every 90 seconds. It first appeared that September, vanished, and then returned in October. The signals began after a landslide triggered by a megatsunami in Dickson Fjord, Greenland, and was thought to have been produced by a seiche, or standing wave. This wave had probably been stirred up by the tsunami and then trapped by ice in the fjord—but there was no way to prove it. Satellite observations were able to document avalanches and the tsunamis they caused, and scientists collected further data in a research station. There was just one problem—the hypothesized seiche was eluding detection. It remained a mystery, even though studies at the time found seismic data that seemed to align with the sloshing motions of standing waves. So, researcher Thomas Monahan of Oxford University decided to take a closer look. Using data from the KaRIn (Ka-band Radar Interferometer) instrument on board NASA's Surface Water Ocean Topography (SWOT) satellite—an international collaboration capable of high-resolution measurements that extended into Dickson fjord—Monahan and his team finally found evidence for a seiche whose waves were slowly losing intensity. 'Based on the seismic attribution, and systematic ruling out of other dynamic phenomena, we conclude that the observed variability in the SWOT data is consistent with that of a slowly decaying seiche,' the team wrote in a study recently published in Nature Communications. Seiches can occur in lakes and other enclosed (or partially enclosed) bodies of water. The tsunami unleashed in Dickson Fjord had enough strength to leave powerful winds and sudden atmospheric pressure shifts in its wake, pushing water from one end of the enclosure to the other. The water then sloshed back and forth, oscillating for anywhere from hours to days after winds ceased. Tsunamis are often seismic phenomena, and the very long period (VLP) seismic signal that came from the fjord was the aftermath of a tsunamigenic landslide. Previous attempts at recording evidence for this particular seiche had been thwarted by the limitations of satellite altimeters, which did not pick up data during extended gaps between observations. They were also not able to record the differences in the height of waves beyond the area directly under the satellite. They were, however, able to get an especially accurate read on the water below. The landslides in Dickson Fjord happened right when SWOT was transitioning to its Science phase, during which it would orbit and survey most of the planet's surface from an altitude of 890 km (553 miles) for 21 days. This orbit was purposely out of sync with the Sun to lower the chances of misidentifying signal frequencies. The researchers went through the data from every pass the satellite made over the region for the weeks in September and October and used this data to create maps of the fjord, modeling it how would have behaved during different times after the landslide and the height differences between waves (which reached up to two meters, or about 6.5 feet). Reconstructions of weather conditions ruled out all other possible causes behind the signal, and convinced scientists that it could only have been caused by a seiche. 'This study shows how we can leverage the next generation of satellite earth observation technologies to study these processes,' Monahan said in a recent press release. 'SWOT is a game changer for studying oceanic processes in regions such as fjords which previous satellites struggled to see into.' You Might Also Like The Do's and Don'ts of Using Painter's Tape The Best Portable BBQ Grills for Cooking Anywhere Can a Smart Watch Prolong Your Life?
Yahoo
05-06-2025
- Science
- Yahoo
We've Finally Seen The Skyscraper Tsunami That Shook Earth For 9 Days
In September 2023, Earth rumbled. Seismic monitoring all over the globe registered a strange signal that repeated every 90 seconds over a whopping nine days, petering out in a way never before seen. Then the same thing happened a month later. Subsequent analysis of those signals determined that the cause of that trembling was likely a giant megatsunami rocking back and forth, slapping against the sides of a fjord in Greenland – generating a standing wave known as a seiche. Now, scientists have finally actually seen the event, in satellite data captured while the event was in progress. It's the observation needed to confirm that the cause of the seismic signal was indeed a seiche, giving us an answer to the age-old question: if a seiche forms in a Greenland fjord and no one is around to see it, does it shake the planet? "This study is an example of how the next generation of satellite data can resolve phenomena that has remained a mystery in the past," says ocean engineer Thomas Adcock of the University of Oxford in the UK. "We will be able to get new insights into ocean extremes such as tsunamis, storm surges, and freak waves. However, to get the most out of these data we will need to innovate and use both machine learning and our knowledge of ocean physics to interpret our new results." According to the analysis of the seismic data, the trigger that unleashed the megatsunami was a melting glacier that sent two giant landslides toppling into the remote Dickson fjord in East Greenland. The resulting splashes generated powerful tsunamis that, with nowhere else to go, sloshed back and forth for days, reaching a peak height of 7.4 to 8.8 meters (24.3 to 28.9 feet). Because of the remote location, however, no one actually saw either event – not even a military vessel that visited the fjord three days into the first one. But humanity has eyes in the sky. There's a satellite mapping technique called altimetry that measures the height of the surface of the planet (including bodies of water) based on how long it takes a radar signal to travel down to the surface and bounce back up again. Most altimetry measurements were unable to record the seiches, because the resolution isn't high enough and the measurements are taken too far apart in time. But a NASA mission launched in 2022 called the Surface Water Ocean Topography (SWOT) satellite has an instrument that is able to take measurements of the height of water with unprecedented precision. The satellite just so happened to have taken measurements at intervals during the days following both events. So the researchers on the new study used this data, collected by SWOT's Ka-band Radar Interferometer, to compile elevation maps of the fjord. Their results showed clear and significant height variations in the water, which was rising as a 2-meter standing wave reverberating back and forth across the fjord. That was it: the team had finally laid eyes on the seiches that were thought to have sent such strange signals rumbling around the world. The next step was to link the two phenomena. By comparing their observations to seismic data, the researchers were able to reconstruct the characteristics of each wave, and the evolution of each event, even for time periods that the satellite had not observed. They were able to rule out other possible explanations for the seismic signals, and confirm that the seiches were responsible. It's a beautifully tidy result that will help us study such events in the future. "Climate change is giving rise to new, unseen extremes. These extremes are changing the fastest in remote areas, such as the Arctic, where our ability to measure them using physical sensors is limited," says engineer Thomas Monahan of the University of Oxford. "This study shows how we can leverage the next generation of satellite Earth observation technologies to study these processes. SWOT is a game changer for studying oceanic processes in regions such as fjords which previous satellites struggled to see into." The research has been published in Nature Communications. Astronauts Reveal The Shocking Beauty of Lightning From Space Sloths The Size of Elephants Roamed America, Before Abruptly Vanishing This Giant Snail Lays Eggs Out of Its Neck… Yes, Seriously
