Tonga eruption sent enough water to fill 58,000 Olympic pools into the atmosphere

The event is expected to warm up the Earth temporarily.
Ameya Paleja
Umbrella cloud generated by the underwater eruption of the Hunga Tonga-Hunga Ha’apai volcano on Jan. 15, 2022.NASA Earth Observatory image by Joshua Stevens
  • The Tonga eruption was 500 times more powerful than Hirsoshima.
  • Water vapor was detected by NASA's Aura satellite.
  • Water content is expected to temporarily warm up the Earth.

When the undersea Hunga Tonga-Hunga Ha’apai volcano erupted near Tonga earlier this year, the shock sent 146 teragrams of water vapor into the stratosphere, a recently published study by NASA scientists said. A teragram of water is equal to a trillion grams.

The volcano eruption that made headlines earlier this year was 500 times more powerful than the atomic bombs that were dropped on Hiroshima and cut off the island nation from the rest of the world for over a month. The sonic boom that accompanied the eruption traveled the world twice, and the waves from the shock sent tsunami warning bells ringing in different parts of the world.

However, it is the amount of water vapor that the eruption has sent up that has caught the attention of scientists since it can have an impact on the planet's temperature and warm it up temporarily. NASA scientists estimate that the single event has sent up 10 percent of water vapor that is already present in the atmosphere.

How did scientists detect the water vapor in the atmosphere?

The Microwave Limb Sounder (MLS) instrument on NASA's Aura satellite first detected the higher levels of water vapor in the stratosphere, which is the layer of atmosphere between 8 and 33 miles (12 and 53 km) above the Earth's surface. The Aura satellite measures water vapor and ozone content in this layer, but the readings were off the charts after the Tonga eruption.

“We had to carefully inspect all the measurements in the plume to make sure they were trustworthy,” said Luis Millán, an atmospheric scientist at NASA’s Jet Propulsion Laboratory, which designed and built the MLS instrument.

Since NASA started measuring eruptions nearly two decades ago, only two eruptions, one in Alaska in 2008 and another in Chile in 2015, have managed to send up significant amounts of water. The Tonga eruption, however, has reduced these major events to mere blips.

How did so much water reach the atmosphere? What impact will it have?

The most likely explanation for the sheer amount of water dissipated is the location of the volcano's caldera - a basin-shaped depression that usually forms after the magma erupts or drains from a shallow chamber beneath the volcano, NASA said on its website. At about 490 feet (150 m), the caldera was at the right depth to inject water into the atmosphere.

If it were located deeper, the pressure of the ocean's depths would have muted the eruption. If it were located at a shallow depth, there wouldn't have been enough seawater to superheat and send out.

While massive eruptions send out vast plumes of ash, dust, and gas that reflect the sunlight back into space and cool the Earth, water vapor sent out by this volcano can be expected to trap more heat and raise the surface temperatures in the short term. This additionally trapped heat, is unlikely to "noticeably exacerbate climate change effects," NASA said.

The findings of the study have been published in Geophysical Research Letters.

Abstract

Following the 15 January 2022 Hunga Tonga-Hunga Ha'apai eruption, several trace gases measured by the Aura Microwave Limb Sounder (MLS) displayed anomalous stratospheric values. Trajectories and radiance simulations confirm that the H2O, SO2, and HCl enhancements were injected by the eruption. In comparison with those from previous eruptions, the SO2 and HCl mass injections were unexceptional, although they reached higher altitudes. In contrast, the H2O injection was unprecedented in both magnitude (far exceeding any previous values in the 17-year MLS record) and altitude (penetrating into the mesosphere). We estimate the mass of H2O injected into the stratosphere to be 146 ± 5 Tg, or ∼10% of the stratospheric burden. It may take several years for the H2O plume to dissipate. This eruption could impact climate not through surface cooling due to sulfate aerosols, but rather through surface warming due to the radiative forcing from the excess stratospheric H2O.

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