Hunga Tonga Eruption Study Shows Methane Destruction in Volcanic Plume

Hunga Tonga Eruption: A Volcanic Methane Paradox

A massive volcanic eruption in January 2022 both released and destroyed significant amounts of methane, a potent greenhouse gas, in a chemical process that has surprised scientists.

The Eruption

In January 2022, the submarine volcano Hunga Tonga-Hunga Ha'apai erupted in the South Pacific. One of the most violent eruptions in modern times, it generated a tsunami and a sonic boom, releasing a plume of ash, steam, and gas that reached approximately 40 miles into the stratosphere.

Scientific Findings

Satellite observations using the TROPOMI instrument on the Sentinel-5P spacecraft detected record-high concentrations of formaldehyde in the volcanic plume. Researchers tracked the plume for 10 days as it moved across the Pacific Ocean toward South America.

Formaldehyde is a short-lived compound that is typically produced when methane is destroyed in the atmosphere.

The study proposes that the eruption introduced a mixture of salty water vapor and volcanic ash into the stratosphere. When exposed to sunlight, this mixture produced chlorine atoms, which reacted with methane, breaking it down. A similar chemical process was observed in 2023 over the Atlantic Ocean, where Saharan dust mixed with sea spray and sunlight generated chlorine atoms that destroyed methane.

The study estimates the eruption produced approximately 330,000 tons of methane while simultaneously destroying roughly 900 metric tons per day through the identified chemical process.

Attribution and Comments

"When we analysed the satellite images, we were surprised to see a cloud with a record-high concentration of formaldehyde... This showed that the cloud must have been destroying methane continuously for more than a week."
— Dr. Maarten van Herpen, Lead Author, Acacia Impact Innovation BV

Professor Matthew Johnson, co-author from the University of Copenhagen, described the finding as "new—and completely surprising."

"How do you prove that methane has been removed from the atmosphere? ... Here we address that problem by showing that methane breakdown can in fact be observed using satellites."
— Dr. Jos de Laat, Senior Author, Royal Netherlands Meteorological Institute

Pete Edwards, an atmospheric chemist at the University of York not involved in the research, commented that the findings are "very difficult" to confirm, noting that the use of only formaldehyde observations does not address uncertainties in atmospheric chemistry.

Emily Dowd, a climate scientist at the University of Leeds, stated that the proposed chemistry still needs to be thoroughly tested in atmospheric models.

Implications

Methane is a greenhouse gas that traps approximately 80 times more heat than carbon dioxide over a 20-year period and is responsible for roughly one-third of current global warming. The study suggests that the identified chemical process could potentially be used to destroy methane emissions at the source, such as by injecting iron-based particles into the atmosphere over the ocean.

• Experts caution that such methods would require further research on safety and effectiveness.
• They note significant differences between the conditions in the stratospheric eruption plume and those in the lower troposphere where such applications would occur.
• The findings may inform revisions to the global methane budget to account for dust from volcanic eruptions or other natural sources.