Melting Antarctic ice sheet could trigger larger volcanic eruptions

Schematic diagram of the thermomechanical magma chamber model simulating ice release obtained in this study. Transparent arrows represent ice export as a decrease in ice layer thickness over time. Credit: Geochemistry, Geophysics and Earth Systems (2024). DOI: 10.1029/2024GC011743
Melting ice sheets are often synonymous with climate change in the media, with evocative images of a lone polar bear floating on a shrinking raft of ice. While impacts such as sea level rise and changes in salinity are well documented, one of the lesser known impacts is the impact on volcanoes.
During deglaciation, ice sheets several kilometers thick melt, reducing the mass that weighs down on land, leading to uplift. This changes the pressure within the magma chamber below the earth’s surface, causing a volcanic eruption.
The study, published in the journal Geochemistry, Geophysics, Geosystems, shows that the melting of the Antarctic ice sheet (isotropic repulsion) is causing massive unloading in one of Earth’s largest volcanic regions, which has seen more than 100 eruptions. This suggests that certain West Antarctic rift valleys are experiencing more frequent and larger eruptions. Center.
Brown University researcher Allie Kunin and colleagues investigated the interaction between ice ages and volcanic activity over the past two planetary glacial cycles (within the past 150,000 years).
To do this, they used a thermomechanical magma chamber model and simulated the shrinking West Antarctic Ice Sheet by inputting specific pressure reductions on the underlying rock and magma chamber.
They further explain how this decrease in confining pressure causes the magma chamber to expand volumetrically, with the associated overpressure and release of volatiles from the basaltic magma (here, when dissolved water and carbon dioxide form bubbles). We investigated whether the release would affect the trajectory of future eruptions.


Results of modeling the pressure change within the magma chamber as a function of the ice expulsion rate and the equivalent mass of ejected magma over 3,000 years. Credit: Coonin et al., 2024.
The research team studied magma chambers of different sizes and found that larger magma chambers are more susceptible to ice mass evacuation, and the rate of evacuation is the key factor, with the highest ice loss rate studied per year. It was discovered that 3 meters.
Moreover, when scientists tested magma chambers that were not saturated with volatiles, they found that the ejection of ice blocks could delay the process of initial volatile release (the initiation of the first stage leading to an eruption) by several decades. It turns out that it was several hundred years earlier.
This means that eruptions occurred that might not have occurred had the unloading not caused changes in the magma chamber, resulting in more cumulative ejection of magma over the lifetime of the magma chamber.
To test their findings, Kunin and his colleagues turned to volcanic deposits in the Andes Mountains of South America. Here, between 18,000 and 35,000 years ago, the Patagonian ice sheet grew up to 1,600 meters thick on top of the Southern Volcanic Belt. They link the release of ice mass during the deglaciation at the end of the Last Glacial Maximum (approximately 18,000 years ago) with increased eruptive activity from the Calbuco, Mocho Choxuenco, and Puyehue Cordon Caul volcanoes. We identified correlations.


The cumulative volume record of eruptions from three volcanoes in the southern Andean volcanic belt corresponds to glacial cycles over the past 150,000 years. Credit: Coonin et al., 2024.
Volcanic activity caused by such unloading can lead to unhelpful positive feedback loops. This is because when ice melts and the pressure in the magma chamber changes, causing an eruption, the result is more ice melting, which can trigger another eruption. In particular, the West Antarctic Ice Sheet lies below sea level, so as the ice melts and sea levels rise, it will become further submerged, accelerating its retreat.
Further complicating the problem are the effects of global warming and rising carbon dioxide levels that cause ice-albedo feedbacks, where melting ice sheets reduce the amount of incoming solar radiation reflected back into space (‘ (fewer “white” reflective surfaces compared to “dark” reflective surfaces). (absorbed by surfaces), warming the atmosphere and worsening dissolution.
Researchers say that even if anthropogenic warming were to stop immediately, the effects of the ice shedding that the West Antarctic Rift system is already experiencing will affect volcanic activity here for thousands of years to come. Pointed out.
Therefore, understanding the sensitivity of the release of this ice mass from the West Antarctic Ice Sheet into magma chambers has important implications in being able to accurately predict future impacts on Earth’s interconnected geological systems. I have it.
Further information: AN Coonin et al, “Magma chamber response to ice unloading: Application to volcanism in the West Antarctic Rift,” Geochemistry, Geophysics, Earth Systems (2024). DOI: 10.1029/2024GC011743
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