Friction Means the Antarctic Ice Sheet May be More Sensitive to Climate Change Than Expected

Antarctic glaciers may be more sensitive to climate change than we thought. Scientists have found that future rates of melt for the West Antarctic Ice Sheet will increase due to a force called Coulomb friction, a type of friction generated by solid surfaces sliding against one another.

The West Antarctic Ice Sheet holds enough ice to be able to raise global sea levels by up to 16 feet. In addition, its physical location makes it susceptible to melting by warm ocean water. That's why scientists decided to take a closer look at the ice sheet to see how likely it would be for it to melt.

Most of West Antarctica's ice sheet is grounded on a sloping rock bed that lies below sea level. In the past decade or so, scientists have focused on the coastal part of the ice sheet where the land ice meets the ocean, called the "grounding line," as vital for accurately determining the melting rate of ice in the southern continent. In other words, friction partly determines the rate at which the ice sheet melts.

"Our results show that het stability of the whole ice sheet and our ability to predict its future melting is extremely sensitive to what happens in a very small region right at the grounding line," said Andrew Thompson, co-author of the new study, in a news release. "It is crucial to accurately represent the physics here in numerical models."

Many earlier models of ice sheet dynamics attempted to simplify calculations by assuming that ice loss is controlled solely by viscous stresses, which are forces that apply to "sticky fluids" such as honey or flowing ice. This means that the models accounted for the flow of ice around obstacles, but ignored friction. In this latest model, though, the scientists found that while Coulomb friction affects only a relatively small zone on an ice sheet, it can have a major impact on ice stream flow and overall ice sheet stability.

If the model is correct, it could have important implications for predicting ice loss in Antarctica as a result of climate change. In fact, for any given increase in temperature, the model predicts a bigger change in the rate of ice loss than is forecast in other models.

The findings are published in the Journal of Glaciology.

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