NEW YORK (AP) – When an undersea volcano erupted off Tonga in January, its watery blast was huge and unusual, and scientists are still trying to understand its impacts.
The volcano, known as Hunga Tonga-Hunga Ha’apai, spewed millions of tons of water vapor 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 where humans live and breathe, by about 5%.
Now, scientists are trying to figure out how all that water might affect the atmosphere and whether it could warm the Earth’s surface in the coming 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 tend to cool the planet. Most volcanoes send up large amounts of sulfur, which blocks the sun’s rays, said Matthew Toohey, a climate researcher at the University of Saskatchewan who was not involved in the study.
The Tongan eruption was much wetter: The eruption started under the ocean, so it shot up 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 rather than lower them, Toohey said.
It’s not clear how much warming there might be.
Karen Rosenlof, a climate scientist with the National Oceanic and Atmospheric Administration who was not involved in the study, said she expects the effects to be minimal and temporary.
“This amount of increase could warm the surface a small amount for a short period of time,” Rosenlof said in an email.
Water vapor will stick in the upper atmosphere for several years before entering 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 from about 7.5 miles to 31 miles (12 km to 50 km) above 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. In general, these tools can’t even measure water levels in the stratosphere because the amounts are so low, Voemel said.
Another research group monitored the explosion using an instrument on a NASA satellite. In their study, published earlier this summer, they estimated that the eruption was even larger, adding about 150 million metric tons of water vapor to the stratosphere, three times more than the study found from Voemel.
Voemel acknowledged that the satellite images may have observed parts of the plume that the balloon instruments could not pick up, making his estimate higher.
Either way, he said, the Tongan explosion was unlike anything seen in recent history, and studying its aftermath may provide new insights into our atmosphere.
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The Associated Press Department of Health and Science is supported by the Department of Science Education at the Howard Hughes Medical Institute. The AP is solely responsible for all content.
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