The study examines how the massive 2022 eruption changed the chemistry and dynamics of the stratosphere

When the Tonga-Hunga Haapai volcano erupted on January 15, 2022 in the South Pacific, it produced a shock wave that was 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, according to a recent study published in the journal Proceedings of the National Academy of Sciences from the Harvard John A. Paulson School of Engineering and Applied Science (SEAS) and the University of Maryland.

According to the research, the reason behind these weather changes is the huge amount of water vapor that was injected into the stratosphere by the undersea volcano. The stratosphere is located about 8-30 miles above the Earth’s surface, and is where the protective ozone layer is located.

“The Hunga-Tonga-Hapai eruption was truly exceptional because it pumped about 300 billion pounds of water into the normally dry stratosphere, which is an absolutely incredible amount of water from a single event,” said David Wilmoth, one of the projects. scientist at SEAS and first author of this paper.

“This eruption put us in uncharted territory,” said Ross Salawicz, a professor at the University of Maryland’s Interdisciplinary Earth System Science Center and co-author of the study. “Never in the history of satellite records have we seen the injection of this much water vapor into the atmosphere, and our research is the first to look at the downstream consequences over large areas of both hemispheres in the months following the eruption using satellite data and a global model.” “.

The Honga Tonga-Hunga Haapai eruption was the largest atmospheric explosion ever recorded. The explosion led to the release of aerosols and gases deep into the stratosphere. Some of the material reached the lower mesosphere, more than 30 miles above the Earth’s surface, heights never recorded from a volcanic eruption. Previous studies found that the eruption increased stratospheric water vapor by 10% worldwide, with higher concentrations in some regions of the Southern Hemisphere.

Wilmoth, Slawicz and the rest of the research team used data from the Microwave Limb Sounder (MLS) instrument aboard the NASA Aura satellite, not only to track how water vapor moves around the world but also to monitor temperature and chlorine monoxide (ClO) levels. Ozone (O₃), nitric acid (HNO₃), and hydrogen chloride (HCl) in the stratosphere for the year following the eruption. They then compared those measurements to data collected by MLS from 2005 to 2021 before the eruption.

The team found that injecting water vapor and sulfur dioxide (SO₂) changed both the chemistry and dynamics of the stratosphere. In terms of chemistry, SO₂ It led to an increase in sulfate aerosols, providing new surfaces for chemical reactions to occur.

“Some reactions that may not happen at all or happen only slowly could happen faster if there was aerosol available on which these reactions could occur,” Wilmoth said. “SO injection₂ From the volcano allowed the formation of sulphate aerosols and the presence of water vapor led to additional production of sulphate aerosols.”

The increase in sulfate aerosols and water vapor set off a cascade of events in complex atmospheric chemistry, which led to widespread changes in the concentrations of a number of compounds, including ozone.

The excess water vapor also had a cooling effect in the stratosphere, causing a change in circulation, resulting in decreased ozone in the Southern Hemisphere and increased ozone over the tropics.

The researchers found that the peak ozone decline occurred in October, nine months after the eruption.

“We saw this huge increase in water vapor in the stratosphere with modest increases in sulfate that set off a cascade of events that led to significant changes in temperature and circulation, ClO, HNO₃hydrochloric acid, O₃“And other gases,” Wilmoth said.

Next, the researchers hope to continue the study by following the impact of the volcano into 2023 and beyond, as water vapor moves from the tropics and mid-latitudes to the pole in the Southern Hemisphere, where it has the potential to amplify Antarctic ozone loss. Water vapor is expected to remain high in the stratosphere for several years.

The research was co-authored by James Anderson, the Philip S. Weld for Atmospheric Chemistry at SEAS; Frija Osterstrom and Jessica Smith.