Scientists explain how Tonga's global tsunami 'jumped' from one ocean to another

A new study published in Nature explains the mechanism behind the generation and propagation of an unusual tsunami that occurred after the colossal explosion of the Hunga Tonga- Hunga Ha'apai in Tonga, early in 2022.

Scientists consider that the tsunami that followed the colossal explosion of the Hunga Tonga-Hunga Ha‘apai volcano, on January 15, 2022, was exceptional: it had a global reach, higher propagation speed, reached unexpected wave heights and had an unprecedented duration.

“The violent explosion of the Hunga Tonga-Hunga Ha'apai volcano in the South Pacific was a source of both noticeable atmospheric waves and an exceptionally fast-travelling global tsunami with minimal dissipation in the far-field. This was the first time that a volcano-triggered tsunami was globally recorded by modern, worldwide dense instrumentation, thus providing a unique opportunity to investigate the role of air-water coupling processes in tsunami generation and propagation” explains Rachid Omira, first author, researcher at Instituto Dom Luiz, Faculty of Sciences of the University of Lisbon (Portugal).

In this study, the research team analyzed satellite, sea-level and atmospheric data worldwide and demonstrated through numerical and analytical models that the tsunami was driven by an acoustic-gravity wave caused by the volcano explosion and travelled several times across the globe. In their findings, the authors provide the exact explanation of the globally observed tsunami and suggest hazard implications for such events.

“The challenging part of studying the Tonga tsunami was to quantitatively explain all the observed tsunami features that were completely different from those of common tsunamis”, adds Rachid Omira, stating: “A fast-moving atmospheric wave able to excite the ocean surface and pump energy into it was our explanation for this tsunami that “jumped” from an ocean to another and reached the coast of Portugal 10 hours earlier than expected”.

The study was led by researchers from Instituto Dom Luiz (Faculty of Sciences of the University of Lisbon) and the Portuguese Institute for Sea and Atmosphere (IPMA), together with researchers from Cardiff University (UK) and the Spanish Institute of Natural Products and Agrobiology (IPNA-CSIC).

More information about this study can be found in:

Omira, R. et al. Global Tonga tsunami explained by a fast-moving atmospheric source. Nature (2022). https://doi.org/10.1038/s41586-022-04926-4