On January 15, 2022, the eruption of the Hunga Tonga-Hunga Ha’apai volcano in the South Pacific not only sent shockwaves globally but also triggered tsunamis in various regions, including Tonga, Fiji, New Zealand, Japan, Chile, Peru, and the United States.
A recent study, published in the Proceedings of the National Academy of Sciences by researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the University of Maryland, reveals that the aftermath of this volcanic event had profound consequences on the stratosphere over the following year. The study indicates unprecedented losses in the ozone layer, with reductions of up to 7% observed over extensive areas of the Southern Hemisphere.
The primary driver behind these atmospheric changes, as per the research findings, was the substantial amount of water vapor introduced into the stratosphere by the underwater eruption. The stratosphere, located approximately 8–30 miles above the Earth’s surface, houses the protective ozone layer.
David Wilmouth, a project scientist at SEAS and the lead author of the study, emphasized the extraordinary nature of the eruption, stating, “The Hunga Tonga-Hunga Ha’apai eruption was truly extraordinary in that it injected about 300 billion pounds of water into the normally dry stratosphere, which is just an absolutely incredible amount of water from a single event.”
Ross Salawitch, a professor at the University of Maryland and co-author of the study, highlighted the unprecedented scale of water vapor injection into the atmosphere. He noted, “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.”
This volcanic event marked the largest explosion ever recorded in the atmosphere, propelling aerosols and gases deep into the stratosphere, reaching altitudes of more than 30 miles above the Earth’s surface. The resulting increase in water vapor in the stratosphere was found to be 10% globally, with even higher concentrations in specific areas of the Southern Hemisphere.
The research team, utilizing data from the Microwave Limb Sounder (MLS) aboard the NASA Aura satellite, tracked the movement of water vapor across the globe and monitored various atmospheric parameters for a year post-eruption. The injection of water vapor and sulfur dioxide (SO2) induced changes in both the chemistry and dynamics of the stratosphere. The presence of SO2 led to an increase in sulfate aerosols, providing new surfaces for chemical reactions.
The study revealed a cascade of events in atmospheric chemistry, initiated by increased sulfate aerosols and water vapor, resulting in widespread changes in the concentrations of compounds, including ozone. The additional water vapor induced cooling in the stratosphere, altering circulation patterns, leading to ozone decreases in the southern hemisphere and an increase over the tropics.
The researchers identified October, nine months after the eruption, as the peak period of ozone depletion. The team aims to extend the study into 2023 and beyond, monitoring the movement of water vapor from the tropics to the Southern Hemisphere pole, where it could potentially exacerbate ozone losses in the Antarctic. The elevated water vapor is expected to persist in the stratosphere for several years.
The co-authors of the study include James Anderson, the Philip S. Weld Professor of Atmospheric Chemistry at SEAS, as well as Freja Østerstrøm and Jessica Smith.
Impact of the Hunga Tonga volcanic eruption on stratospheric composition – Proceedings of the National Academy of Sciences
Study examines how massive 2022 eruption changed stratosphere chemistry and dynamics – Phys.org
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