Two separate studies released this week are announcing a bleak future for the West Antarctic Ice Sheet — and an accompanying sea-level rise across the globe. Both groups of researchers conclude that global warming is accelerating the disintegration of large parts of the ice sheets, and that the melting that is already under way is likely unstoppable. This, the researchers say, will eventually cause global sea levels to rise by at least 10 feet.
The first study, published today in Science by researchers at the University of Washington, used computer modeling and topography maps to conclude that the collapse of the Thwaites Glacier, an extremely large glacier flowing into Pine Island Bay, is already underway. This process, the researchers say, could be completed within the next few centuries and would cause the ocean to rise by nearly 2 feet. Furthermore, because that glacier is currently acting as a barrier for the rest of the ice sheet, its collapse could ultimately trigger a 10-13 foot rise in global sea levels.
Both studies fundamentally agreeIn contrast, the NASA study, which has been accepted for publication in the journal Geophysical Research Letters, is predicting a 4-foot rise in sea levels as the melting rate accelerates in the Amundsen Sea sector. These predictions are the result of 40 years of observations in the area, which might explain the difference between the University of Washington results and the NASA results. In any case, both studies came to similar conclusions. "We conclude that the disappearance of ice is unstoppable," said NASA glaciologist Eric Rignot during a teleconference today, and "these changes are related in part to climate warming."
Sridhar Anandakrishnan, a professor of geosciences at Pennsylvania State University who participated in the NASA study, added during the teleconference that "the system has chain reactions in place that aren't going to stop." He suggested that the only the glacier retreat could stop is if the glaciers suddenly "had to climb uphill, but we have looked at that, and we are fairly confident that there is no such hill or mountain that could slow down this retreat."
Humans aren't entirely at fault
The melting of the ice, researchers say, isn't taking place because of warm air, but because of warm water in the ocean's depths. Winds in the Antarctic are pulling the water to the surface and causing the ice to melt. This is why the researchers state that global warming is a contributing factor, but not the sole cause: natural, non-human induced changes in climate across the globe might also be at fault.
"The basic idea that we are in this kind of retreat and that it's unstoppable has been around since the 1970s," said cryosphere program NASA scientist Tom Wagner, "but we're finally at this point where we can put all those observations together and say 'Wow, we are really in this state.'" When asked if humans might be able to do something to stop the melt, however, the scientists sound bearish. "If the system, and especially if the thermal ocean forcing, stays the same," Rignot said, "the retreat will be unstoppable."