When the Hengja Tonga-Hung Hapai volcano erupted underwater on January 15, 40 miles (65 kilometers) north of the Tonga capital, it caused a tsunami as well as a sonic boom that rippled across the globe — twice.
The explosion sent a long plume of water vapor into the stratosphere, which lies between 8 and 33 miles (12 and 53 kilometers) above Earth’s surface. That’s enough water to fill 58,000 Olympic-sized swimming pools, according to revelations from NASA satellites.
It was detected by the Microwave Limb Sounder on NASA’s Aura satellite. The satellites measure water vapor, ozone and other atmospheric gases. After the volcanic eruption, scientists were shocked by the water vapor readings.
They estimate that the volcanic eruption sent 146 teragrams of water into the stratosphere. One teragram is equal to one trillion grams, and in this case, it is equal to 10% of the water already in the stratosphere.
That’s almost four times the amount of water vapor that reached the stratosphere after the 1991 eruption of Mount Pinatubo in the Philippines.
“We’ve never seen anything like it before,” study author Lewis Millan, an atmospheric scientist at NASA’s Jet Propulsion Laboratory in Southern California, said in a statement. “We have to carefully check all measurements on the shaft to make sure they are reliable.”
Earth observation
The Microwave Limb Sounder can measure and detect natural microwave signals from Earth’s atmosphere even through thick ash clouds.
“MLS is the only instrument with a sufficiently dense scope to capture plumes of water vapor as they occur, and the only instrument that is not affected by the ash emitted by the volcano,” Millan said.
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The Ora satellite was launched in 2004 and has since measured only two volcanic eruptions that sent large amounts of water vapor into the atmosphere. But moisture from the 2008 Kasatochi event in Alaska and the 2015 Calbuco eruption in Chile dissipated fairly quickly.
The Tonga eruption is different in that the water vapor sent into the atmosphere can trap heat, which can cause surface temperatures to rise. According to the researchers, excess water vapor can remain in the stratosphere for several years.
Additional water vapor in the stratosphere can also cause chemical reactions that temporarily contribute to the depletion of Earth’s protective ozone layer.
eruption anatomy
Fortunately, the warming effect of water vapor is expected to be small and temporary, and will disappear as excess steam is reduced. Researchers don’t think it will be enough to exacerbate current conditions due to the climate crisis.
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Researchers believe that the main reason for the high amount of water vapor is the depth of the volcano’s caldera 490 feet (150 meters) below sea level.
If it were too deep, the researchers say, the depth of the ocean would dampen the eruption, it would be too shallow, and the amount of seawater heated by rising magma would not match what had reached the stratosphere.
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