Tonga eruption study suggests volcanic plume may help break down methane

A new study has found that the 2022 eruption of the Hunga Tonga-Hunga Ha'apai underwater volcano may have triggered a chemical process that helped destroy methane in the atmosphere. The research focuses on the massive blast in the Tongan archipelago in the southern Pacific Ocean, which sent gas nearly 40 miles above the Earth's surface. Scientists say the eruption, one of the most powerful in modern history, may also have produced an unusually large cloud of formaldehyde, a sign that methane was being broken down.

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The findings were published in Nature Communications and are based on satellite observations of the eruption plume. Researchers detected formaldehyde in a place and at a scale where it would not normally be expected, according to one of the study authors, Maarten van Herpen, a physicist and executive director at Acacia Impact Innovation. The team believes sunlight interacting with salty water vapour and volcanic ash in the stratosphere generated chlorine, which then helped destroy methane.

The study says the eruption injected enough salty water vapour into the stratosphere to fill around 58,000 Olympic-sized swimming pools. The eruption was at least hundreds of times more powerful than the Hiroshima nuclear bomb, and it triggered a tsunami and a sonic boom that circled the planet twice. In the new analysis, scientists tracked the formaldehyde cloud for 10 days.

Because formaldehyde usually survives only a few hours in the atmosphere, its persistence suggested methane destruction was continuing for more than a week. The researchers estimate the eruption released around 330,000 tonnes of methane, with roughly 900 tonnes broken down each day. The study matters because methane is one of the most potent greenhouse gases, and any process that helps remove it from the atmosphere is of interest to climate scientists.

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The work also builds on earlier research over the Atlantic Ocean, where Saharan dust, sea salt spray and sunlight were found to generate chlorine atoms that can help destroy methane. In this case, the Tonga eruption appears to have created a similar chemistry in a volcanic plume, offering a rare natural example of atmospheric methane removal. The Hunga Tonga-Hunga Ha'apai eruption in January 2022 was already known for its scale and unusual atmospheric effects.

It blasted material high into the stratosphere and caused disruption far beyond the Pacific region through the tsunami and global sonic boom. The new study adds a different dimension to that event by suggesting the plume itself may have altered atmospheric chemistry in a way that reduced some of the methane it emitted. What remains unclear is how broadly this process could apply outside a volcanic eruption, or whether it could be replicated in any practical way.

The study points to a specific mix of salty vapour, ash and sunlight, and scientists will need to determine how common such conditions are. For now, the findings offer a better understanding of how extreme natural events can affect greenhouse gases, while leaving open questions about their wider climate significance.

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