When the Hunga Tonga-Hunga Ha’apai volcano erupted beneath the Pacific Ocean on January 15, 2022, the blast launched a colossal plume of water to a height of 53 kilometers (33 miles). Using satellite data, researchers have now calculated that the event transferred roughly 146 billion kilograms (322 billion pounds) of water into the stratosphere, where it could remain for up to a decade and contribute to the degradation of the ozone layer.
As tsunamis fanned out across the Pacific following the eruption, the Microwave Limb Sounder (MLS) – which sits aboard NASA’s Aura satellite – immediately got to work observing changes in the sulfur dioxide and water content of the Earth’s atmosphere.
Having now analyzed this data, the authors of a new study in the journal Geophysical Research Letters report that the amount of sulfur dioxide released was roughly comparable to that of previous eruptions, but that the quantity of water ejected was “unprecedented in both magnitude (far exceeding any previous values in the 17-year MLS record) and altitude (penetrating into the mesosphere).”
“This is not surprising since the Hunga Tonga-Hunga Ha'apai caldera was formerly situated 150 meters [492 feet] below sea level,” they add. When you also consider that the eruption was the most powerful of the 21st century, you start to get a picture of just how much seawater was blown sky high. Overall, the researchers estimate that the event increased the total water content of the stratosphere by about 10 percent.
Usually, large volcanic eruptions have a cooling effect on the planet as the sulfur compounds they eject reflect sunlight away from the Earth’s atmosphere. Water, on the other hand, absorbs the Sun’s energy, which means that such a massive increase in stratospheric water content could exacerbate global warming.
Furthermore, the study authors explain how water molecules reacting with oxygen atoms in the atmosphere could lead to an increase in hydroxide, which may then contribute to ozone depletion via a process known as the hydroxyl radical cycle.
To make matters worse, the researchers expect the sulfur dioxide released by the eruption to dissipate within two to three years, but say that the water plume could hang around in the atmosphere for “five to 10 years”. In other words, the warming effect of the water vapor is likely to outlast the cooling impact of the eruption.
As a result, the authors conclude that Hunga Tonga-Hunga Ha'apai “may be the first volcanic eruption observed to impact climate not through surface cooling caused by volcanic sulfate aerosols, but rather through surface warming caused by excess H2O radiative forcing.”