Tonga eruption blasted unprecedented amount of water into stratosphere – SpaceRef

When the Hunga Tonga-Hunga Ha’apai volcano erupted on January 15, it sent a tsunami around the world and triggered a sonic boom that went around the globe twice. The underwater eruption in the South Pacific also ejected an enormous plume of water vapor into Earth’s stratosphere – enough to fill more than 58,000 Olympic-size swimming pools. The sheer amount of water vapor could be enough to temporarily affect Earth’s global average temperature.

“We’ve never seen anything like it,” said Luis Millán, an atmospheric scientist at NASA’s Jet Propulsion Laboratory in Southern California. He led a new study examining the amount of water vapor the Tonga volcano injected into the stratosphere, the layer of the atmosphere between about 8 and 33 miles (12 and 53 kilometers) above Earth’s surface.

In the study, published in Geophysical Research Letters, Millán and his colleagues estimate that the Tonga eruption ejected about 146 teragrams (1 teragram equals 1 trillion grams) of water vapor into Earth’s stratosphere — equivalent to 10% of the water already present in this atmosphere Layer. That’s almost four times the amount of water vapor that scientists ejected into the stratosphere when Mount Pinatubo in the Philippines erupted in 1991.

Millán analyzed data from the Microwave Limb Sounder (MLS) instrument on NASA’s Aura satellite, which measures atmospheric gases, including water vapor and ozone. After the Tonga volcano erupted, the MLS team began seeing water vapor readings that were off the charts. “We had to carefully examine all measurements in the cloud to make sure they could be trusted,” Millán said.

A lasting impression

Volcanic eruptions rarely inject much water into the stratosphere. In the 18 years that NASA has been measuring, only two other eruptions — the 2008 Kasatochi event in Alaska and the 2015 Calbuco eruption in Chile — have ejected significant amounts of water vapor to such high altitudes. But these were minor outliers compared to the Tonga event, and the water vapor from the previous two eruptions quickly dissipated. The excess water vapor injected by the Tonga volcano, on the other hand, could remain in the stratosphere for several years.

This extra water vapor could affect atmospheric chemistry and speed up certain chemical reactions that could temporarily exacerbate ozone depletion. It could also affect surface temperatures. Massive volcanic eruptions like Krakatoa and Mount Pinatubo usually cool the Earth’s surface by ejecting gases, dust, and ash that reflect sunlight back into space. In contrast, the Tonga volcano did not eject large amounts of aerosols into the stratosphere, and the huge amounts of water vapor from the eruption could have a small, transient warming effect because water vapor traps heat. The effect would dissipate as the extra water vapor leaves the stratosphere and would not be enough to noticeably amplify the effects of climate change.

The sheer volume of water injected into the stratosphere was likely only possible because the underwater volcano’s caldera — a basin-shaped depression that usually forms after magma eruptions or outflow from a shallow chamber beneath the volcano — was just the right depth in the ocean : approximately 490 feet (150 meters) in depth. The shallower, and there would not have been enough seawater, superheated by the erupting magma, to account for the stratospheric water vapor levels Millán and his colleagues saw. Any deeper, and the immense pressure at the ocean depths could have dampened the eruption.

The MLS instrument was well positioned to see this plume of water vapor as it observes natural microwave signals radiating from Earth’s atmosphere. By measuring these signals, MLS can “see” through obstructions such as ash clouds that can blind other instruments that measure water vapor in the stratosphere. “MLS was the only instrument with sufficient coverage to capture the water vapor plume as it happened and the only one that wasn’t affected by the ash that the volcano was releasing,” Millán said.

The MLS instrument was designed and built by JPL, which is managed for NASA by Caltech in Pasadena. NASA’s Goddard Space Flight Center manages the Aura mission.