NEW YORK (AP) – When an undersea volcano erupted in Tonga in January, its watery explosion was huge and unusual – and scientists are still trying to understand its effects.
The volcano, known as Hunga Tonga-Hunga Ha’apai, released millions of tons of water vapor into the atmosphere, according to a study published Thursday in the journal Science.
The researchers estimate that the eruption raised the amount of water in the stratosphere – the second layer of the atmosphere, above the range where people 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 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.
Major eruptions usually cool the planet. Most volcanoes emit large amounts of sulfur, which block the sun’s rays, explained Matthew Toohey, a climate researcher at the University of Saskatchewan who was not involved in the study.
The Tongan explosion was much more tragic: The eruption started under the ocean, so it released plumes with much more water than usual. And since water vapor acts as a heat-trapping greenhouse gas, the eruption is likely to raise temperatures rather than lower them, Toohey said.
It is not clear how much warming there might be.
Karen Rosenlof, a climate scientist at the National Oceanic and Atmospheric Administration who was not involved in the study, said she expects the effects to be minimal and temporary.
“This increased volume may warm the surface slightly for a short period of time,” Rosenlof said in an email.
The water vapor will stick around the upper atmosphere for a few years before making its way into the lower atmosphere, Toohey said. Meanwhile, the extra water could 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 measured the volcano’s plumes using a network of instruments suspended from weather balloons. Normally, these instruments can’t even measure water levels in the stratosphere because the amounts are so low, Voemel said.
Another research group monitored the blast 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 Voemel’s study found.
Voemel acknowledged that the satellite imaging may have observed parts of the plume that the balloon instruments could not capture, causing his estimate to be higher.
Either way, he said, the explosion in Tongan was unlike anything seen in recent history, and studying its aftermath could provide new insights into our atmosphere.
The Associated Press Department of Health and Science is supported by the Department of Science Education of the Howard Hughes Medical Institute. The AP is solely responsible for all matters.