Research on Tonga’s devastating 2022 Hunga eruption has just been published in the journal Nature Geoscience.

“Submarine volcanism has previously been overlooked in global climate studies, because there is typically not much atmospheric sulphur dioxide released,” says Professor Shane Cronin, a co-lead author of the study with postdoctoral fellow Dr Jie Wu.

However, while sulphur dioxide can lead to significant climate effects, so too can water vapour.

At its peak Hunga’s eruption injected up to 3 billion tonnes of steam into the atmosphere in a single hour, with the water vapour reaching the stratosphere and even the mesosphere more than 57 km up, Cronin says.

“The eruption has been shown by several recently published studies to have cooled the Southern Hemisphere and cause a range of other atmospheric and climate impacts that we are still discovering,” he adds.

Hunga had the potential for a global impact from sulphur dioxide. The team estimates 20 million tonnes of it was released during the eruption, however, most of the sulphur went directly into seawater at depths between 300m and 1100m.

Cronin is at the School of Environment at Waipapa Taumata Rau, University of Auckland, while Wu is now based at the University of Otago.

University of Auckland and staff and students have been working with Tongan partners to understand the wider implications of submarine volcanism in the Southwestern Pacific in the aftermath of Hunga, the largest eruption witnessed in the modern era.

“We are striving to understand the broader hazards of submarine volcanism including tsunami and damage to shorelines and internet data cables as well as how these eruptions affect our environment and climate,” says Cronin.

The work is supported by an MBIE Endeavor Research Programme grant from 2024.