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The powerful eruption of the Hunga Tonga-Hunga Ha'apai underwater volcano rocked the island nation of Tonga on January 15, 2022. The spectacular 13-mile-wide explosion is the largest recorded in the 21st century thus far. It expelled ash and gas plumes as high as 19 miles and triggered tsunami warnings across the Pacific.
Now, NASA atmospheric scientists have discovered that the underwater volcano also blasted 160,900 tons (146,000 metric tons) of water vapor into the Earth's stratosphere. This is enough to fill 58,000 Olympic-sized swimming pools. It is the largest moisture injection into the stratosphere since NASA began taking measurements in 1995.
"We estimate that the excess water vapor is equivalent to around 10 percent of the amount of water vapor typically residing in the stratosphere." NASA researchers wrote in the study published in Geophysical Research Letters on July 1, 2022.
The team, led by Luis Millán, attributes the unprecedented amount of water vapor to the fact that the explosion occurred at just the correct depth in the ocean: about 490 feet (150 meters). Any shallower, and there wouldn’t have been enough seawater superheated by the erupting magma to send to the stratosphere. Any deeper and the eruption would have been muted by the immense pressure of the ocean water.
The researchers believe the excessive moisture may react with the oxygen in the stratosphere to produce hydroxide. If that happens, it could temporarily weaken the ozone layer, which protects us from the Sun's harmful ultraviolet radiation.
The water vapor may also impact global temperatures
Massive volcano eruptions typically cool the Earth's atmosphere. The gases, dust, and ash block the sunlight from reaching the planet's surface. However, the Tonga volcano did not send large amounts of volcanic material into space, and most of the ash it spewed quickly fell to the ground. Hence, researchers had initially concluded the underwater explosion would not impact the Earth's climate.
But the discovery of the water vapor has changed that. Since moisture traps heat, the volcano explosion may produce a small temporary warming effect. If true, the Tonga eruption will be the first on record to increase the Earth's temperature. The researchers believe the impact will last only a few years and vanish once the extra water vapor cycles out of the stratosphere.
"It is just a temporary warming, and then it will go back to whatever it was supposed to go back to," Millán noted. "It's not going to exacerbate climate change."
On a more positive note, the water may reduce the amount of methane — one of the leading greenhouse gases contributing to climate change — in the atmosphere. The scientists say this could counter some of the anticipated warming.
Resources: JPL,NASA.gov, Livescience.com, phys.org