Volcanic impact of Tonga eruption on Ozone layer

When the Hunga Tonga–Hunga Ha’apai underwater volcano erupted on 15 January 2022, it injected an unprecedented amount of water vapour into the atmosphere, rapidly depleting the ozone layer.

Researchers used balloon measurements, sky observations and satellite data to investigate the impacts of the eruption of the Tonga volcano on the ozone layer, publishing their results in Science.

These measurements show the eruption released significant amounts of water vapour into the atmosphere, reaching very high altitudes of up to 55 kilometres.

The large amounts of water vapour led to higher relative humidity and radiative cooling, which created the conditions for increased chemical processes involved in ozone depletion.

Within a week, stratospheric ozone levels above the southwestern Pacific and Indian Ocean region had decreased by 5%, a significant decline exceeding the impact of previous eruptions.

Dr Olaf Morgenstern, principal atmosphere and climate scientist at New Zealand’s National Institute of Water and Atmospheric Research (NIWA), describes the ozone depletion in the aftermath of the eruption as “highly unusual”.

“The Hunga-Tonga Hunga-Haapai eruption was the biggest eruption of the satellite era, in terms of explosive power, altitude of the plume, and particularly in how much water it injected into the stratosphere. Usually there are roughly four million water molecules per million in the stratosphere, and the volcanic plume contained up to 300,” he says.

The observations may help explain why the hole in the Ozone layer expanded to one of the largest on record (when measured on 16 September by the European Space Agency).

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