While the inhabitants of Tonga struggle to recover from a devastating volcanic explosion has left the Pacific island nation incinerated with ash and submerged in water, scientists are trying to better understand the eruption’s global effects.
They already know the answer to an important question: While this appears to be the largest eruption in the world in three decades, Saturday’s eruption of the Hunga volcano will most likely have no effect. temporary cooling of the global climate, as some have previously had massive eruptions.
But in the aftermath of this event, there could be short-term effects on weather in parts of the world and possible minor disruptions in radio transmissions, including those used by global positioning systems.
The shock wave generated by the explosion, as well as the unusual nature of the tsunami it produced, scientists will have to study this event for years. Tsunamis were detected not only in the Pacific but also in the Atlantic, Caribbean and Mediterranean.
“It’s not that we don’t know about volcanic explosions and tsunamis,” said Lori Dengler, professor emeritus of geophysics at Humboldt State University in California. “But to see that with the state-of-the-art orchestra that we have is unprecedented.”
The explosion of the underwater volcano, officially known as Hunga Tonga-Hunga-Haʻapai, produced dangerous ash in the region, including the Tongan capital Nuku’alofa, about 40 miles to the south. The capital also experienced a 4-foot tsunami and higher wave heights have been reported elsewhere.
The government called the eruption an “unprecedented disaster”, even though Full range of damage It is difficult to determine because the explosion tore the undersea telecommunications cables and the ash that forced the closure of Tonga’s airports.
Beyond Tonga, however, the magnitude of the explosion was clear. Satellite images show a cloud of dirt, rock, volcanic gas and water vapor hundreds of miles across, and a narrower plume of gas and debris rising nearly 20 miles into the atmosphere.
Some volcanologists have compared it to the catastrophic explosion of Krakatau in Indonesia in 1883 and the most recent major eruption, Mount Pinatubo in the Philippines, in 1991.
Pinatubo erupted over several days, sending about 20 million tons of sulfur dioxide gas into the stratosphere, or upper atmosphere. There, the gas combines with water to create aerosol particles that reflect and scatter some of the sun’s rays, keeping them from hitting the surface.
That had the effect of cooling the atmosphere by about 1 degree Fahrenheit (about half a degree Celsius) for several years. (This is also the mechanism of a controversial form of geoengineering: using airplanes or other means to continuously pump sulfur dioxide into the stratosphere to intentionally cool the planet.)
Shane Cronin, a volcanologist at the University of Auckland in New Zealand who has studied previous eruptions in New Zealand, said the Hunga eruption “matches the strength of Pinatubo at the time. climax”.
But the eruption in Hunga lasted only about 10 minutes, and satellite sensors in the days that followed measured about 400,000 tons of sulfur dioxide reaching the stratosphere. “The SO2 emissions are much smaller than that of Mount Pinatubo,” said Michael Manga, professor of earth sciences at the University of California, Berkeley.
So unless the eruption in Hunga continues and continues at a similar magnitude, which is considered unlikely, it will have no global cooling effect.
Dr. Cronin said the strength of the eruption was partly related to its location, about 500 feet underwater. When superheated molten rock, or magma, hits seawater, the water instantly rises into steam, expanding the explosion many times over. If it is much deeper, the water pressure will reduce the explosion.
The shallower depths, he said, created the perfect “almost Goldilocks” conditions for the intense discharge of the explosion.
Corwin Wright, an atmospheric physicist at the University of Bath in the UK, said the explosion created a shock wave in the atmosphere. Satellite measurements show that the wave has reached beyond the stratosphere, reaching 60 miles high and traveling around the world at more than 600 miles per hour.
“We’re seeing a really big wave, the biggest we’ve ever seen in the data that we’ve used in 20 years,” said Dr. “We’ve never seen anything that really covers the entire Earth like this, and certainly not from a volcano.”
The wave formed when the force of the explosion displaced large amounts of air outward and upward into the atmosphere. But then gravity pulled it down. It then rises again, and this up-and-down oscillation continues, creating an alternating wave of high and low pressure that moves outward from the source of the detonation.
Dr. Wright says that although the wave appears high in the atmosphere, it could potentially have a short-term effect on weather patterns closer to the surface, perhaps indirectly by affecting the jet stream.
“We don’t know very well,” he said. “We are looking to see what happens in the next few days. It can be just rippled and non-interactive. “
Dr. Wright said that because the wave was so high, it could also slightly affect the transmission of radio waves and signals from the satellites of the global positioning system.
Barometric pressure waves may also play a role in the anomalous tsunamis that have occurred.
Tsunamis are created by the rapid displacement of water, usually by rock movement. Large underwater faults can create tsunamis as they move during an earthquake.
Volcanoes can also cause tsunamis. In this case, the underwater explosion, and the crater’s collapse, may have caused the displacement. Or one side of the volcano may have become unstable and collapsed, with similar results.
But that would only explain the local tsunami that flooded Tonga, the scientists said. Normally, says Gerard Fryer, an associate researcher at the University of Hawaii at Manoa who previously worked at the Pacific Tsunami Warning Center, “you would expect that the energy would decay by approximately way.”
But the event produced tsunamis comparable in size to the local one, and over several hours, in Japan, Chile, and the West Coast of the United States, and eventually produced small tsunamis in other parts of the country. other basins around the world.
It’s an indication that as it moved through the atmosphere, the pressure wave may have impacted the ocean, causing it to oscillate as well.
It will take weeks or months to analyze the data to determine if that’s what happened, but some researchers say that could be one explanation.
Dr Dengler said: “We know that the atmosphere and the ocean are coupled. “And we saw the tsunami in the Atlantic. It didn’t go around the tip of South America to get there. “
“The evidence is very clear that pressure waves have played a role. The question is how big a part”.
https://www.nytimes.com/2022/01/19/climate/scientists-tonga-volcano-eruption-effects.html Here’s What Scientists Know About the Tonga Volcanic Eruption