The highest volcanic plume on record: the Hunga Tonga-Hunga Ha’apai eruption

A new analysis by researchers at the University of Oxford has shown that the devastating Hunga Tonga-Hunga Haʻapai eruption in January 2022 created the highest volcanic plume on record. At 57 km high (35 miles), the ash cloud generated by the eruption is also the first to have been observed in the mesosphere, a layer of the atmosphere more commonly associated with shooting stars.

Using images captured by satellites, researchers have confirmed that the January 2022 eruption of the Hunga Tonga-Hunga Ha’apai volcano produced the highest plume on record. The colossal eruption is also the first directly observed to have passed through the mesosphere layer of the atmosphere. The results, by a team of scientists from

” data-gt-translate-attributes=”[{” attribute=””>University of Oxford’s Department of Physics and RAL Space, were published on November 3 in the journal Science.

On January 15, 2022, Hunga Tonga–Hunga Haʻapai, a submarine volcano in the Tongan archipelago in the southern Pacific Ocean, violently erupted. The explosion was one of the most powerful ever observed, sending shock waves around the world and triggering devastating tsunamis that left thousands homeless. A towering column of ash and water was ejected into the atmosphere – but until now, scientists lacked an accurate way to measure just how tall this was.

The full Earth disk seen by Japan’s Himawari-8 satellite, the volcanic eruption is in the lower right. Credit: Simon Proud / Uni Oxford, RALSpace NCEO / Japan Meteorological Agency.

Normally, the height of a volcanic plume can be estimated by measuring the temperature recorded at the top by infrared-based satellites and comparing this to a reference vertical temperature profile. This is because in the troposphere (the first and lowest layer of the Earth’s atmosphere), temperature decreases with height. But if the eruption is so large that the plume penetrates into the next layer of the atmosphere (the stratosphere), this method becomes ambiguous because the temperature begins to increase again with height (due to the ozone layer absorbing solar ultraviolet radiation).

An enlarged view of the Hunga Tonga–Hunga Ha’apai eruption on January 15, 2022, recorded by NOAA’s GOES-17 weather satellite. Credit: Simon Proud and Simeon Schmauß / Uni Oxford, RALSpace NCEO / NOAA

To overcome this problem, the researchers used a new method based on a phenomenon called the “parallax effect”. It is the apparent difference in the position of an object when viewed from multiple lines of sight. You can see this for yourself by closing your right eye and holding out a hand with your thumb up. If you then switch eyes, so that your left is closed and your right is open, your thumb will appear slightly offset from the background. By measuring this apparent change in position and combining it with the known distance between your eyes, you can calculate the distance to your thumb.

An enlarged view of the eruption, taken by Japan’s Himawari-8 satellite at 04:10 UTC on January 15, 2022, about 10 minutes after the eruption began. Credit: Simon Proud / Uni Oxford, RALSpace NCEO / Japan Meteorological Agency

The location of the Tonga volcano is covered by three geostationary weather satellites, so the researchers were able to apply the parallax effect to the aerial images they captured. Above all, during the eruption itself, the satellites recorded images every 10 minutes, making it possible to document the rapid changes in the trajectory of the plume.

The results showed that the plume reached an altitude of 57 kilometers (35 miles) at its highest point. This is significantly higher than previous record holders: the 1991 eruption of Mount Pinatubo in the Philippines (40 km / 25 miles at its highest point) and the 1982 eruption of El Chichón in Mexico (31 km / 19 miles). It also makes the plume the first observed evidence of a volcanic eruption injecting material through the stratosphere and directly into the mesosphere, which begins about 50 km (31 miles) above the Earth’s surface.

An enlarged view of the eruption, taken by Japan’s Himawari-8 satellite at 04:50 UTC on January 15, 2022, about 50 minutes after the eruption began. Credit: Simon Proud / Uni Oxford, RALSpace NCEO / Japan Meteorological Agency

“This is the first time we have recorded a volcanic plume reaching the mesosphere. Krakatau in the 1800s might have done just as well, but we haven’t seen that in enough detail to confirm that,” said National Center for Earth Observation senior scientist Dr Simon Proud. University of Oxford and Council for Science and Technology Facilities. Installation of RAL space.

“This is an extraordinary result because we have never seen a cloud of such size before,” Proud added. “Also, the ability to estimate height like we did (using the parallax method) is only possible now that we have good satellite coverage. This wouldn’t have been possible a while ago. ten years. “

An enlarged view of the eruption, taken by Japan’s Himawari-8 satellite at 05:40 UTC on January 15, 2022, about 100 minutes after the eruption began. Credit: Simon Proud / Uni Oxford, RALSpace NCEO / Japan Meteorological Agency

The Oxford researchers now intend to build an automated system to calculate the heights of volcanic plumes using the parallax method.

Co-author Dr Andrew Prata of the Atmospheric, Oceanic and Planetary Physics Sub-Department added: “We would also like to apply this technique to other eruptions and develop a plume height dataset that can be used by volcanologists and atmospheric scientists. model the dispersion of volcanic ash in the atmosphere. Other scientific questions we would like to understand are: why did the Tonga plume rise so high? What will be the climatic impacts of this eruption? And what exactly was the plume made of? »

Reference: “The January 2022 eruption of the Hunga Tonga-Hunga Ha’apai volcano reached the mesosphere” by Simon R. Proud, Andrew T. Prata and Simeon Schmauß, November 3, 2022, Science.
DOI: 10.1126/science.abo4076

Besides the University of Oxford, the study also involved the Rutherford Appleton Laboratory and the National Center for Earth Observation in Harwell, as well as the University of Applied Sciences in Munich.

The three satellites used to capture and assess the eruption were GOES-17 (USA), Himawari-8 (Japan) and GeoKompSat-2A (Korea). The open-access data was processed by the British Jasmin supercomputer at the Science and Technology Facilities Council’s Rutherford Appleton Lab.