The undersea volcano that erupted in January this year off Tonga spewed more than ash and volcanic gases into the air; it also expelled an amount of water vapor equivalent to 58,000 Olympic-sized swimming pools, according to a study published in the journal Geophysical Research Letters.
All that water vapor could end up being the most damaging factor in the eruption, as it will potentially deplete the ozone layer and intensify the effects of global warming.
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In the new study, researchers used data from NASA’s Aura satellite to ascertain the amount of water released into the stratosphere, the second layer of the atmosphere, which extends from 7 to 50 km high.
The results revealed that an additional 160,900 tons of water vapor had entered the atmosphere since the eruption, reaching an altitude of 53 km. This is the highest quantity and height ever reached by such a phenomenon since satellites began to analyze the atmosphere.
“We estimate that excess water vapor is equivalent to 10% of the amount typically found in the stratosphere,” the study authors state. They add that this amount of steam will remain in the stratosphere for approximately 50 years.
This amount of water comes from the fact that the eruption took place at a depth of 150 meters in the middle of the Pacific Ocean. When the volcano became active, the seawater that came into contact with the magma quickly superheated, which resulted in a large amount of “explosive steam”. This is one of the reasons the explosion was so powerful.
Typically, large-scale eruptions release large amounts of ash and gases, such as sulfur dioxide, which can create reflective compounds in the atmosphere. These chemicals can prevent the sun’s rays from reaching the Earth’s surface, which results in a cooling of the atmosphere.
However, the eruption in Tonga produced low levels of sulfur dioxide compared to events of the same magnitude. In addition, most of the ash expelled quickly precipitated to the Earth’s surface.
So experts initially concluded that the explosion would have minimal effects on the planet’s climate. However, they only looked at sulfur dioxide levels and didn’t factor in excess water, which can be just as problematic.
All that water, according to the study’s authors, can warm the atmosphere as much as greenhouse gases. This means that the eruption in Tonga may be the first to cause the atmosphere to warm rather than cool.
The researchers also signaled that such a sudden rise in water vapor could decrease the amount of ozone in the stratosphere, potentially weakening the ozone layer, which protects Earth from excess ultraviolet rays from the Sun. This is because H2O molecules in the stratosphere can, over time, become OH ions, which, reacting with ozone, result in oxygen and even more water.
On the other hand, the researchers also speculate that this “injection” of water vapor can rid the atmosphere of a considerable amount of methane (CH4), one of the gases responsible for the greenhouse effect, since the same OH ions that react with the ozone can interact with methane and produce a methyl radical that concentrates less heat in the atmosphere compared to CH4. This is expected to counterbalance the warming caused by the reaction with ozone.
The authors, however, claim it is too early to predict the eruption’s exact climatic effects. “It is essential that we continue to monitor volcanic gases from this and future eruptions to better quantify their roles in climate,” the scientists say.
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