The atmospheric acoustic gravity wave caused by the massive explosion of the Hunga Tonga-Hunga Ha’apai volcano in the South Pacific on January 15 was the source of a global tsunami. The conclusion was made by a team of researchers from the Dom Luis Institute, the Faculty of Natural Sciences of the University of Lisbon and the Portuguese Institute of the Sea and Atmosphere (IPMA).
Using a combination of sea level data, atmospheric and satellite images from various parts of the globe, to which they applied numerical and analytical models, the scientists demonstrated that “the tsunami was caused by a constantly moving source in which acoustic gravity waves were emitted. eruptions excite the ocean and transfer energy to it through resonance, ”says a study published in the journal Nature under the title “Global tsunami in Tonga attributed to fast moving atmospheric source”.
The coincidence between the tsunami and the time of arrival of these acoustic-gravity waves confirms, according to the researchers, the existence of a direct connection between these two phenomena. “The massive volcanic explosion created noticeable atmospheric waves and an exceptionally fast global tsunami,” comments lead author Rashid Omira, researcher at Instituto Dom Luiz and IPMA.
The geophysicist cites as an example the fact that the tsunami hit the coast of Portugal, on the opposite side of the planet (more than 17 thousand kilometers), “ten hours earlier than expected”, crossing the oceans and causing sea waves of amazing sizes. , has remote areas.
“This was the first time that a tsunami caused by a volcanic eruption was recorded on a global scale with modern and dense equipment around the world, which provided a unique opportunity to study the processes of interaction between air and water during its occurrence and propagation,” says Omira.
Volcanic eruptions usually cause tsunamis but are now less likely to have transoceanic effects. In Portugal, according to IPMA information released at the time, “sea level changes” were observed in the Azores, Madeira and the mainland. In Ponta Delgada, the water level rose by 40 cm, in Peniche by 39 cm, and in Funchal by 20 cm.
“This tsunami spread across different oceans, including the Atlantic, while sea level fluctuations were observed at almost all mareographic stations operating on the Portuguese coast, fluctuations with an amplitude of less than half a meter,” IPMA then said.
The eruption of an underwater volcano a few kilometers from Tonga raised a cloud of ash and gases into the sky, reaching a height of 20 kilometers. Tsunami waves damaged New Zealand, Chile, Peru and the United States.
