Volcanic ash plume on January 16, 2022 over South Pacific due to eruption of Hunga Tonga-Hunga Haʻapai, as seen from the International Space Station. Credit: NASA Earth Observatory
Key points:
- The Hunga Tonga-Hunga Ha’apai eruption was the largest explosion ever recorded in the atmosphere.
- It injected so much water vapor and sulfur dioxide that it changed both the chemistry and the dynamics of the stratosphere.
- Researchers expect the water vapor to stay elevated in the stratosphere for a period of several years.
When the Hunga Tonga-Hunga Ha’apai volcano erupted on Jan. 15, 2022 in the South Pacific, it produced a shock wave felt around the world and triggered tsunamis in Tonga, Fiji, New Zealand, Japan, Chile, Peru and the United States. It also changed the chemistry and dynamics of the stratosphere in the year following the eruption, leading to unprecedented losses in the ozone layer of up to 7% over large areas of the Southern Hemisphere.
Driving those atmospheric changes, according to new research published in PNAS, was the sheer amount of water vapor injected into the stratosphere by the undersea volcano. The location of the stratosphere is approximately 8 - 30 miles above Earth’s surface and is where the protective ozone layer resides.
That amount of water is incredibly uncommon in a volcanic eruption.
“This eruption put us in uncharted territory,” said Ross Salawitch, professor at the University of Maryland’s Earth System Science Interdisciplinary Center and co-author of the study. “We’ve never seen, in the history of satellite records, this much water vapor injected into the atmosphere and our paper is the first that looks at the downstream consequences over broad regions of both hemispheres in the months following the eruption using satellite data and a global model.”
Comparing data from 2005 to 2021 prior to the eruption, researchers found that the injection of water vapor and sulfur dioxide (SO2) changed both the chemistry and the dynamics of the stratosphere. In terms of chemistry, the SO2 led to an increase of sulfate aerosols, which provided new surfaces for chemical reactions to occur.
The increased sulfate aerosols and water vapor kicked off a chain of events in the complex atmospheric chemistry that led to widespread changes in the concentrations of a number of compounds, including ozone. The extra water vapor also had a cooling effect in the stratosphere, leading to a change in circulation, which drove decreases in ozone in the southern hemisphere and an increase of ozone over the tropics. The researchers found that the peak decrease in ozone occurred in October, nine months after the eruption.
Next, the researchers hope to continue the study by following the impact of the volcano into 2023 and beyond as the water vapor moves from the tropics and midlatitudes to the Southern Hemisphere pole, where it has the potential to amplify ozone losses in the Antarctic. The water vapor is expected to stay elevated in the stratosphere for a period of several years.