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Climate effects of volcanoes beneath the waves
Volcanoes erupting underwater have a distinctive effect on the climate that is larger and more widespread than previously thought, according to an international group led by University of Auckland and Tongan scientists.
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.
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Shane Cronin, Professor of Volcanology at the University of Auckland, and co-lead author of this study:
The massive 2022 eruption of Hunga volcano in Tonga was devastating to the country due to the impacts of enormous tsunami that wiped out entire villages. On a global scale, the eruption produced the largest plume ever seen, reaching the stratosphere and even into the mesosphere more than 57 km above the volcano.
"The climatic events of this eruption have been felt world-wide, with recent reports highlighting an overall southern Hemisphere cooling as well as many other atmospheric impacts which we are still learning about.
"The unusual feature of this huge volcano-climate impact from Hunga is that it was not caused by sulphur – like for other major events in the past (e.g., 1991 Pinatubo, Philippines, the second-highest eruption plume ever measured).
"The Hunga eruption was under the sea throughout the entire 11 hour event. This meant that hot magma interacted with seawater and almost all of the 20 million tonnes of sulphur released by the eruption went into the ocean.
"The submarine explosions may have shielded us from the effects of sulphur dioxide in the atmosphere, but it had an unforeseen impact of turning huge amounts of sea-water into steam (up to a few billion tonnes). This steam rapidly rose above the volcano and drove the eruption plume to its record heights. The wet-plume hydrated the upper atmosphere, causing a range of climatic impacts that are still being studied world wide.
