It is the conclusion of a study based on 4,000 computer simulations to study how the loss of the ice sheet affects buried volcanoes in Antarctica, led by Allie Coonin of Brown University. The findings are published in the journal Geochemistry, Geophysics, Geosystems.
A slow climate feedback cycle may be brewing beneath the vast Antarctic ice sheet. The continent, divided from east to west by the Transantarctic Mountains, includes volcanic giants such as Mount Erebus and its iconic lava lake. But at least 100 less conspicuous volcanoes dot Antarctica, many of them clustered along its western coast. Some of those volcanoes peak above the surface, but others lie several kilometers below the Antarctic ice sheet.
Climate change is causing the ice sheet to melt, raising global sea levels. The melting is also taking weight off the rocks below, with more local consequences. Ice sheet melting has been shown to increase volcanic activity in subglacial volcanoes in other parts of the world.
More and larger subglacial eruptions
In the case of Antarctica, gradual melting could increase the number and size of subglacial eruptions. The reason is that this unloading of the ice sheets reduces the pressure on the magma chambers below the surface, causing the compressed magma to expand. This expansion increases pressure on the walls of the magma chamber and can cause eruptions.
Some magma chambers also contain large amounts of volatile gases, which normally dissolve in the magma. As the magma cools and when the overburden pressure is reduced, those gases come out of solution like carbonation from a freshly opened soda bottle, increasing the pressure in the magma chamber. This pressure means that melting ice can accelerate the onset of a subglacial volcano eruption, reports the American Geophysical Union (AGU) journal Eos.
Consequences for the ice sheet
Eruptions from subglacial volcanoes may not be visible on the surface, but they can have consequences for the ice sheet. The heat from these eruptions can increase ice melting deep below the surface and weaken the overlying ice sheet, potentially leading to a feedback loop of reduced pressure from the surface and more volcanic eruptions.
Coonin and his team emphasize that this process is slow and takes place over hundreds of years. But that means the theoretical feedbacks could continue even if the world reduces anthropogenic warming. The Antarctic ice sheet was much thicker during the last ice age, and the same process of discharge and expansion of magma and gas may have contributed to past eruptions.
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