Glacier retreat could lead to volcanic eruptions worldwide, including in Antarctica: Study

As climate change speeds up glaciers retreat, hundreds of dormant subglacial volcanoes worldwide — particularly in Antarctica — could become active, leading to more frequent and explosive eruptions, warned scientists during a presentation at the Goldschmidt Conference, an international meeting on geochemistry being held in Prague.

Volcanoes can also erupt under ice sheets and glaciers. These sub-glaciated volcanoes are present in currently and formerly glaciated regions of the world, particularly Iceland, British Columbia and Antarctica.

Antarctica is the largest glaciovolcanic province globally, with volcanoes occurring all the way from the sub-Antarctic South Sandwich Islands, through the Antarctic Peninsula and Marie Byrd Land, and into East Antarctica, a distance of about 5,000 kilometres.

The connection between glacier retreat and volcanic eruptions is not new. The link between the two has been known in Iceland since the 1970s.

A 2022 study published in the journal Bulletin of Volcanology suggested that heavy rainfall and melting of glaciers might lead to frequent and severe volcanic eruptions.

“Our study suggests this phenomenon is not limited to Iceland, where increased volcanicity has been observed, but could also occur in Antarctica. Other continental regions, like parts of North America, New Zealand and Russia, also now warrant closer scientific attention,” Pablo Moreno-Yaeger from the University of Wisconsin-Madison, United States, said during the presentation in Prague.

Moreno-Yaeger and his colleagues arrived at these findings after studying six volcanoes, including the now-dormant Mocho-Choshuenco volcanoes, one of the most hazardous volcanoes in Chile's Southern Volcanic Zone), in the Chilean Andes. The team used dating tools to study eruptions and analysed crystals in erupted rocks to understand how the weight and pressure of glacial ice alter the characteristics of magma underground.

Their analysis showed that during the peak of the last ice age between 26,000–18,000 years ago, the thick ice cover suppressed the volume of eruptions, allowing a large reservoir of silica-rich magma to accumulate 10-15 km under the surface. But as the ice age ended and the glaciers retreated, there was a sudden loss of weight, causing the crust to relax and gasses in the magma to expand. This buildup of pressure triggered explosive volcanic eruptions from the deep reservoir, causing the volcano to form, the researchers said.

“Glaciers tend to suppress the volume of eruptions from the volcanoes beneath them. But as glaciers retreat due to climate change, our findings suggest these volcanoes go on to erupt more frequently and more explosively. The key requirement for increased explosivity is initially having a very thick glacial coverage over a magma chamber, and the trigger point is when these glaciers start to retreat, releasing pressure — which is currently happening in places like Antarctica,” Moreno-Yaeger explained.

Rapid deglaciation, according to the 2022 paper, can lead to high magma release. Ice stresses the Earth’s crust, causing magma to stay put. But when the ice retreats, the pressure reduces, causing magma to rise to the surface. “Essentially, the glacier is pushing the crust down into the mantle. When the weight of the ice is removed, the crust slowly ‘floats’ upwards again,” Jamie Farquharson, report co-author and research engineer at the Université de Strasbourg, France, previously told Down To Earth. “This is like holding a rubber duck underwater. When the duck is let go, it bobs back up, Farquharson added.

However, the researchers added that this is a slow process, with the process taking centuries to occur. This suggests that early warning could still be possible. 

As for the climate impacts of volcanic eruptions, the researchers explained that in the short term, eruptions release aerosol (tiny particles in gases) that can temporarily cool the planet. The eruption of Mt Pinatubo in 1991, for instance, cooled the global surface temperature in the Northern Hemisphere by a little over 0.5°C for over a year. 

But these effects are likely to reverse with multiple eruptions. “Over time the cumulative effect of multiple eruptions can contribute to long-term global warming because of a buildup of greenhouse gases,” said Moreno-Yaeger. “This creates a positive feedback loop, where melting glaciers trigger eruptions, and the eruptions in turn could contribute to further warming and melting.”