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Tonga volcanic eruption of 2022 depleted huge amounts of ozone rapidly, research finds

The eruption notably injected an unprecedented amount of water vapour - about 10% of the total global mean stratospheric burden - to very high altitudes of up to 55 kilometres.
Last Updated : 21 October 2023, 10:32 IST
Last Updated : 21 October 2023, 10:32 IST

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New Delhi: The Tongan volcanic eruption of 2022 caused large, rapid depletion of ozone by injecting huge amounts of water vapour into the stratosphere, new research in the journal Science said.

The eruption notably injected an unprecedented amount of water vapour - about 10 per cent of the total global mean stratospheric burden - to very high altitudes of up to 55 kilometres, an international team of researchers from the US and Europe said in their study.

In just the one week following the eruption, the stratospheric ozone above the tropical southwestern Pacific and Indian Ocean region decreased by five per cent. The Antarctic ozone hole depletes up to 60 per cent of ozone from September to November, they said.

This depletion of tropical ozone exceeds that of previous eruptions, underscoring the exceptional nature of the eruption of the submerged Hunga Tonga-Hunga Ha'apai volcano on January 15, 2022, they said.

They combined balloon measurements taken near the Réunion Island in the Indian Ocean, zenith sky observations and satellite data to capture the early evolution of the volcanic plume's impact on ozone, which protects life on the Earth by absorbing harmful and skin-damaging ultraviolet radiations from the Sun.

The scientists say the enhanced water vapour content (humidity) in the stratosphere led to a series of interactions between other components shot out from the volcano, including aerosols, that ultimately broke down ozone over the tropical south-western Pacific and Indian Ocean regions.

"Usually, there are roughly four million water molecules per million in the stratosphere, and the volcanic plume contained up to 300, causing substantial impacts on atmospheric chemistry, increased ozone loss, both due to gas-phase chemistry and in association with the enhanced volcanic aerosol."

"As a result, some highly unusual ozone depletion happened in the tropics in the aftermath of the eruption, especially given the generally small variability of ozone in that part of the world."

"As a result of these observations, the scientific community has been expecting some unusual polar ozone depletion to happen after the volcanic material reached the Antarctic."

"It did not affect the 2022 ozone hole season because the material did not make it to the pole in time. The 2023 ozone hole season, contrary to expectations, has not been unusual. The reasons for Nature not playing ball I'm sure will be explored," said Olaf Morgenstern, principal scientist - Atmosphere and Climate, National Institute of Water and Atmospheric Research (NIWA), New Zealand, who was not involved in the study.

The NIWA was part of a research published in Science journal earlier this year, which found the Tongan eruption recorded the fastest underwater flows of volcanic material ever.

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Published 21 October 2023, 10:32 IST

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