The huge amount of water vapor released into the atmosphere by Tonga’s explosive eruption in January could be enough to temporarily warm the Earth’s surface.
When the Hunga Tonga-Hunga Ha’apai volcano erupted on January 15, it sent a tsunami that swept across the world and caused a sonic boom that circled the globe twice. The submarine eruption in the South Pacific Ocean also spewed a huge plume of water vapor into Earth’s stratosphere, enough to fill more than 58,000 Olympic swimming pools.
“We’ve never seen anything like it,” Luis Millán, an atmospheric scientist at NASA’s Jet Propulsion Laboratory in Southern California, said in a statement. He led a new study looking at how much water vapor the Tonga volcano injected into the stratosphere, the layer of the atmosphere between about 12 and 53 kilometers above the Earth’s surface.
In the study, published in Geophysical Research Letters, Millán and his colleagues estimate that the Tonga eruption sent about 146 teragrams of water vapor into Earth’s stratosphere, which is equivalent to 10% of the water already present in Earth’s stratosphere. this layer of the atmosphere. . That’s nearly four times the amount of water vapor that scientists estimate the 1991 eruption of Mount Pinatubo in the Philippines released into the stratosphere.
Off-Chart Water Vapor Readings
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 inspect all the measurements on the plume to make sure they were reliable,” Millán said.
Volcanic eruptions rarely inject much water into the stratosphere. In the 18 years that NASA has made measurements, only two other eruptions, the 2008 Kasatochi event in Alaska and the 2015 Calbuco eruption in Chile, have sent appreciable amounts of water vapor to such high altitudes. But these were only flashes 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 additional water vapor could influence atmospheric chemistry, leading to certain chemical reactions that could temporarily worsen ozone depletion. It could also influence surface temperatures.
water vapor traps heat
Massive volcanic eruptions like Krakatoa and Mount Pinatubo typically cool the Earth’s surface by expelling gases, dust, and ash that reflect sunlight back into space. In contrast, the Tonga volcano did not inject large amounts of aerosol into the stratosphere, and the huge amounts of water vapor from the eruption may have little temporary warming effect, as the vapor water retains heat. The effect would dissipate as the additional water vapor left the stratosphere and would not be enough to significantly worsen the effects of climate change.
The large amount of water injected into the stratosphere was likely only possible because the submarine volcano’s caldera, a basin-like depression that typically forms after magma erupts or flows from a shallow chamber under the volcano, was at the correct depth in the ocean: about 150 meters below.
Shallower, and there wouldn’t be enough superheated seawater from erupting magma to explain the stratospheric water vapor values that Millán and his colleagues saw. Deeper, and the immense pressures in the deep ocean could have silenced the eruption.
The MLS instrument was well placed to detect this water vapor plume because it sees the natural microwave signals emitted by the Earth’s atmosphere. Measuring these signals allows MLS to “see” through obstacles such as ash clouds that can blind other instruments that measure water vapor in the stratosphere.
“MLS was the only instrument with dense enough coverage to capture the water vapor plume at the time it occurred, and the only one that was unaffected by the ash released from the volcano,” said Millan.