When the Hunga Tonga-Hunga Ha’apai undersea volcano erupted on Jan. 15, 40 miles (65 kilometers) north of Tonga’s capital, it created a tsunami and sonic boom that swept across the globe, twice .
The eruption sent a tall plume of water vapor into the stratosphere, which is between 8 and 33 miles (12 and 53 kilometers) above Earth’s surface. It was enough water to fill 58,000 Olympic swimming pools, according to detections from a NASA satellite.
The detection was made by the Microwave Limb Sounder instrument on NASA’s Aura satellite. The satellite measures water vapor, ozone and other atmospheric gases. After the eruption occurred, scientists were surprised by the water vapor readings.
They estimate that the eruption delivered 146 teragrams of water into the stratosphere. One teragram equals one trillion grams, and in this case it equaled 10% of the water already present in the stratosphere.
That’s nearly four times the amount of water vapor that reached the stratosphere after Mount Pinatubo erupted in the Philippines in 1991.
“We’ve never seen anything like this,” study author Luis Millán, an atmospheric scientist at NASA’s Jet Propulsion Laboratory in Southern California, said in a statement. “We had to carefully inspect all the measurements on the plume to make sure they were reliable.”
Watching the Earth
The Microwave Limb Sounder instrument can measure natural microwave signals from Earth’s atmosphere and detect them even through thick ash clouds.
“MLS was the only instrument with coverage dense enough to capture the water vapor column at the time it happened, and the only one that was not affected by the ash released by the volcano,” Millán said.
The Aura satellite was launched in 2004 and since then has only measured two volcanic eruptions that spewed a substantial amount of water vapor that high into the atmosphere. But water vapor from the 2008 Kasatochi event in Alaska and the 2015 Calbuco eruption in Chile dissipated fairly quickly.
The Tonga eruption was different because the water vapor it sent into the atmosphere can trap heat, which could lead to warmer surface temperatures. The excess water vapor could remain in the stratosphere for several years, according to the researchers.
Additional water vapor in the stratosphere could also lead to chemical reactions that temporarily contribute to the depletion of Earth’s protective ozone.
anatomy of a rash
Fortunately, the heating effect of the water vapor is expected to be small and temporary, and will dissipate as the additional vapor dwindles. The researchers don’t think it’s enough to exacerbate existing conditions due to the climate crisis.
The researchers believe that the main reason for the amount of elevated water vapor was due to the depth of the volcano’s caldera at 490 feet (150 meters) below the ocean surface.
If it were too deep, the depth of the ocean would have silenced the eruption, and if it were too shallow, the amount of seawater heated by the erupting magma would not have matched that which reached the stratosphere, the researchers said.
