On January 15, 2022, the Hunga Tonga-Hunga Ha’apai volcano violently erupted beneath the Pacific Ocean, launching a never-before-seen volume of water vapor into the atmosphere. Now, a new study has found that the vapor sparked a large, rapid depletion in the Earth’s ozone layer.
Last year’s eruption was record-breaking in a number of ways – not only was it the largest natural explosion in a century, but it also triggered a 90-meter-high (295-foot) tsunami wave, an 11-hour lightning storm, and the highest plume ever recorded.
It also launched what researchers estimated to be around 146 billion kilograms (322 billion pounds) of water into the stratosphere, along with other aerosolized volcanic nasties like sulfur dioxide and ash. According to a new study, the presence of water caused these aerosols to become hydrated and in turn, led to the formation of chlorine compounds that can trigger ozone depletion.
"The increase in water vapor following the Hunga-Tonga eruption had a pivotal impact. It raised relative humidity and cooled the upper atmosphere, primarily between 25 and 30 km in altitude. This change in conditions allowed chemical reactions to occur on the surfaces of volcanic aerosols at temperatures higher than their usual range,” explained Stephanie Evan, lead author of the study, speaking to Newsweek.
“The chemical reactions that occurred on the hydrated volcanic aerosols resulted in the creation of reactive chlorine compounds, like chlorine monoxide (ClO), from chlorine compounds that were not typically active, such as hydrogen chloride (HCl)."
The researchers used a combination of balloon measurements, zenith sky observations, and satellite data to track the early aftermath of the eruption, including the chemical reactions that occurred in the plume as it reached the atmosphere. They found that in just one week, the ozone above the tropical southwestern Pacific and Indian Ocean region decreased by 5 percent.
"In simple terms, the volcanic aerosols enabled the formation of substances that could break down ozone, contributing to its reduction. This transformation of chlorine species contributed to the fast reduction of ozone in the upper atmosphere above the tropical southwestern Pacific and Indian Ocean region in the week after the eruption," said Evans.
Whilst they also found that, by the end of January 2022, the rapid depletion of ozone in this region stopped, the researchers cautioned that the impacts of this event will likely be long-lasting; future research should focus on the atmospheric impact of water vapor released in natural disasters, and how this relates to climate change.
"The introduction of a significant amount of water vapor into the upper atmosphere, as observed during the Hunga-Tonga eruption, can have several implications for climate change. Water vapor is a potent greenhouse gas that absorbs heat in the form of infrared radiation from the Earth's surface and subsequently re-emits it,” Evans explained.
“Consequently, the injection of such a substantial quantity of water vapor is expected to contribute to warming in the atmosphere for a period of several years until the gas naturally dissipates," Evan said.
The study is published in Science.