NEW YORK (AP) – When an underwater volcano erupted in Tonga in January, its watery explosion was huge and unusual, and scientists are still trying to understand its impacts.
The volcano, known as Hunga Tonga-Hunga Ha’apai, emitted millions of tons of water vapor high into the atmosphere, according to a study published Thursday in the journal Science.
Researchers estimate that the eruption increased the amount of water in the stratosphere, the second layer of the atmosphere, above the range in which humans live and breathe, by about 5%.
Now, scientists are trying to figure out how all that water could affect the atmosphere and whether it could warm the Earth’s surface in the next few years.
“This was a once-in-a-lifetime event,” said lead author Holger Voemel, a scientist at the National Center for Atmospheric Research in Colorado.
Large eruptions usually cool the planet. Most volcanoes emit large amounts of sulfur, which blocks the sun’s rays, explained Matthew Toohey, a climate researcher at the University of Saskatchewan who was not involved in the study.
The explosion in Tongan was much softer: the eruption started under the ocean, then raised a plume with much more water than usual. And because water vapor acts as a heat-trapping greenhouse gas, the eruption will likely raise temperatures instead of lowering them, Toohey said.
It is unclear how much warming could be in store.
Karen Rosenlof, a climate scientist at the National Oceanic and Atmospheric Administration who was not involved in the study, said she expected the effects to be minimal and temporary.
“This amount of increase could heat up a small amount of surface for a short period of time,” Rosenlof said in an email.
The water vapor will remain in the upper atmosphere for a few years before making its way into the lower atmosphere, Toohey said. Meanwhile, the extra water could also accelerate the loss of ozone in the atmosphere, Rosenlof added.
But it’s hard for scientists to say for sure, because they’ve never seen an eruption like this.
The stratosphere extends about 7.5 miles to 31 miles (12 km to 50 km) above the Earth and is usually very dry, Voemel explained.
Voemel’s team estimated the volcano’s plume using a network of instruments suspended from weather balloons. Usually, these instruments can’t even measure water levels in the stratosphere because the quantities are so low, Voemel said.
Another research team monitored the explosion using an instrument on a NASA satellite. In their study, published earlier this summer, they estimated the eruption to be even larger, adding about 150 million tons of water vapor to the stratosphere, three times as much as Voemel’s study.
Voemel acknowledged that satellite imaging may have observed parts of the plume that the balloon instruments could not capture, making his estimate higher.
Either way, he said, the Tongan explosion was unlike anything seen in recent history, and studying its aftermath could provide new insights into our atmosphere.
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