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The Hunga Tonga-Hunga Ha'apai volcano erupted in the South Pacific on
January 15, 2022. It sent shock waves around the world and caused tsunamis
in Tonga, Fiji, New Zealand, Japan, Chile, Peru, and the United
States.
According to a new study from the Harvard John A. Paulson School of
Engineering and Applied Sciences (SEAS) and the University of Maryland,
the eruption changed the chemistry and dynamics of the stratosphere in the
year that followed. This caused the ozone layer to lose up to 7% of its
thickness over large parts of the Southern Hemisphere, which had never
happened before. The study was published in the Proceedings of the
National Academy of Sciences.
According to the study, those changes in the atmosphere were caused by
the huge amount of water vapor that the underwater volcano put into the
air. The stratosphere is about 8 to 30 miles above the surface of the
Earth. It is where the protective ozone layer is located.
Project scientist at SEAS and lead author of the paper David Wilmouth
said, "The Hunga Tonga-Hunga Ha'apai eruption was truly extraordinary in
that it injected about 300 billion pounds of water into the normally dry
stratosphere. That is just an absolutely incredible amount of water from a
single event."
“This eruption took us to places we have never been before,” said Ross
Salawitch, co-author of the study and professor at the University of
Maryland’s Earth System Science Interdisciplinary Center. "We've never
seen, in the history of satellite records, this much water vapor injected
into the atmosphere and our paper is the first that looks at the
downstream consequences over broad regions of both hemispheres in the
months following the eruption using satellite data and a global
model."
It is known that the Hunga Tonga-Hunga Ha'apai eruption was the biggest
blast ever seen in the sky. Aerosols and gases were thrown high into the
atmosphere by the explosion. Some of it got to the lower mesosphere, which
is more than 30 miles above the Earth's surface. This is the highest level
of material that has ever been found from a volcano erupting. Studies done
in the past found that the eruption raised the amount of water vapor in
the atmosphere by 10% around the world, and in some parts of the Southern
Hemisphere, the levels were even higher.
Aura's Microwave Limb Sounder (MLS) helped Wilmouth, Salawitch, and the
rest of the research team track how the water vapor moved around the
world. They also kept an eye on the temperature and amounts of chlorine
monoxide (ClO), ozone (O3), nitric acid (HNO3), and hydrogen chloride
(HCl) in the stratosphere for a year after the eruption. Then, they
matched those readings to information MLS had gathered from 2005 to 2021,
which was before the eruption.
That adding water vapor and sulfur dioxide (SO2) changed the chemistry
and the movement of things in the atmosphere, the team found. To explain
this chemically, the SO2 caused more sulfate particles to form, which gave
chemicals new places to react.
"Certain reactions that might not happen at all or only happen slowly can
happen faster if there are aerosols available on which those reactions can
take place," stated Wilmouth. "The injection of SO2 from the volcano
allowed sulfate aerosols to form and the presence of water vapor led to
the additional production of sulfate aerosols."
The rise in sulfate particles and water vapor set off a chain of events
in the atmosphere's complicated chemistry that changed the amounts of many
chemicals, including ozone everywhere.
There was less ozone in the southern hemisphere and more over the tropics
because of the change in airflow caused by the extra water vapor. This
caused the stratosphere to cool down.
The most ozone was lost in October, which was nine months after the
earthquake, according to the experts.
"We had this enormous increase in water vapor in the stratosphere with
modest increases in sulfate that set off a series of events that led to
significant changes in temperature and circulation, ClO, HNO3, HCl, O3,
and other gases," said Wilmouth.
Next, the scientists want to keep studying by keeping an eye on the
volcano's effects through 2023 and beyond. They want to see how the water
vapor moves from the tropics and midlatitudes to the poles of the Southern
Hemisphere, where it could make ozone losses worse in the Antarctic. It is
believed that the water vapor will stay high in the atmosphere for a
number of years.
James Anderson, the Philip S. Weld Professor of Atmospheric Chemistry at
SEAS, Freja Østerstrøm, and Jessica Smith all wrote parts of the study
together.
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