It was one of the most powerful volcanic eruptions on the planet and released so much water vapor into the atmosphere that it could temporarily warm the Earth’s surfaceaccording to data collected by a NASA satellite.
The underwater volcano Hunga Tonga, about 65 kilometers from the capital of Tonga, erupted on January 15 this year, causing a tsunami and shock waves that were felt twice in various parts of the world.
The eruption also released a high cloud of water vapor into the stratosphere, a layer located between 12 and 53 kilometers above the Earth’s surface. According to NASA, this amount of water would fill 58,000 Olympic swimming pools.
The calculation was made from data collected by the Microwave Limb Sounder (MLS), a microwave siren that is on NASA’s Aura satellite. This satellite is used to precisely measure water vapour, ozone and other atmospheric gases. “MLS is the only instrument with sufficient coverage to capture the water vapor cloud as it happened, and the only one that was not affected by the ash released by the volcano,” explained expert Luis Millán, quoted by CNN International.
Scientists following the measurements were surprised to see the readings after the eruption of Hunga Tonga, which released 146 teragrams of water into the stratosphere – equivalent to ten percent of the water already present in what is the second largest layer of the Earth’s atmosphere. One teragram equals one billion grams.
For comparison, the scientists explain that this value was four times greater than the amount of water vapor that reached the stratosphere after the eruption of Mount Pinatubo, a volcano in the Philippines, in 1991.
This year’s phenomenon motivated a study, published in July in the journal Geophysical Research Letters. “We have never seen anything like this before”, said in a statement NASA atmospheric scientist and study author Luis Millán. “We had to carefully inspect all of the water vapor cloud measurements to ensure they were reliable.”
Eruption could warm Earth’s surface
NASA’s Aura satellite was launched in 2004. Since then, it had only measured the water vapor released by two volcanic eruptions, as they were the ones that released this vapor higher into the atmosphere: that of the Kasatochi volcano, in Alaska, in 2008 ; and that of Calbuco, in Chile, seven years later. However, the steam from these two eruptions dissipated quickly, unlike what happened now.
Usually, the most powerful volcanic eruptions – such as Mount Pinatubo in the Philippines or Krakatoa in Indonesia – cool the earth’s surface temperature because the gas, dust and ash they expel reflect sunlight.
But with Hunga Tonga, the situation was different. The water vapor that the eruption sent into the atmosphere is able to retain heat, which can lead to warmer temperatures at the surface. In addition, excess water vapor can remain in the stratosphere for several years, according to experts.
That same excess can also lead to chemical reactions that temporarily contribute to the depletion of the Earth’s protective ozone layerwhich filters out ultraviolet solar radiation.
Scientists say, however, that this heating should be small and temporary, dissipating as the excess steam decreases. Therefore, the conditions that already exist due to the climate crisis should not be substantially worsened by this phenomenon.
Explanation may lie in the depth of the caldera
Experts and researchers continue to try to understand why the amount of water vapor released in the Hunga Tonga eruption was so high.
The theory they find most plausible has to do with the depth of the caldera (collapse structure that forms at the center of a volcano)located 150 meters below the surface of the ocean.
Had the caldera been in a deeper zone, the very depth of the ocean would have silenced the eruption. And if it were closer to the surface, the amount of seawater heated by magma (rocky material that turns into lava) would not match the levels of steam that reached the stratosphere.
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