A principal scientist says a “highly unusual” amount of ozone depletion happened in the tropics in the aftermath of the 2022 Hunga-Tonga Hunga-Ha'apai volcanic eruption.
New research, published in the journal Science today, shows the eruption depleted 5% of the ozone layer in some regions in one week.
It details the consequences of the unprecedented amount of water vapour which was shot into the sky, reaching heights of 55km.
Balloon measurements were taken near Réunion Island in the Indian Ocean to understand how volcanic eruptions influence the climate and ozone chemistry for the research.
According to the report, the study "sheds a light" on the complex interactions between a large volcanic eruption and the tropical stratospheric ozone, offering "crucial insights" into atmospheric chemistry and its implications for climate change.
After the eruption took place, the humidity in the stratosphere led to a series of interactions between other components shot out from the volcano which ultimately broke down the ozone over the tropical south-western Pacific and Indian Ocean regions, the authors, led by Dr Stéphanie Evan of the French National Centre for Scientific Research, said.
'Substantial impacts'
Reacting to the research, NIWA atmosphere and climate principal scientist Dr Olaf Morgenstern said the eruption was the “biggest” of the satellite era, in terms of power, altitude of plume, and particularly 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.
“The authors show that this massive local enhancement of water caused 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.
It displaced around 10 cubic kilometres of sea floor, the equivalent of 2.5 million Olympic-sized swimming pools. (Source: 1News)
Despite scientific observations expecting some “unusual polar ozone depletion” to happen after the volcanic material reached the Antartic, it did not affect the 2022 ozone hole season because the material didn't reach the pole in time.
Morgenstern also notes contrary to expectations, the 2023 ozone hole season has not been unusual, and suggests the reasons for nature “not playing ball” will be explored.
"This article focuses on the immediate consequences where totally unprecedented conditions (at least as far as records of stratospheric composition go) caused large, interesting, and scientifically relevant shifts in atmospheric composition that advance our understanding of atmospheric chemistry more generally.
'Fascinating snapshot'
University of Canterbury school of physical and chemical sciences associate professor Dr Laura Revell said the eruption is surprising because of the large quantities of water vapour which was injected into the stratosphere.
“The measurements made in this study show that the stratospheric cooling from the water vapour helped the ozone loss processes involving volcanic aerosol to become more efficient.
“Ozone decreased rapidly by 5% in just one week over the tropical south-western Pacific and Indian Ocean. This is a significant amount, but not as large as the Antarctic ozone hole, where around 60% of the ozone layer is depleted between September and November each year.”
Revell adds the study is a “fascinating snapshot” of what happened in the stratosphere in the aftermath of the eruption, however the consequences of the event are “not over”.
“The increased stratospheric water vapour may linger for several years yet. Time – and continued atmospheric monitoring – will tell."
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