Student Studies Ice Sheet Melting
A Dartmouth-led study finds that rising temperatures and ash from Northern Hemisphere forest fires combined to cause large-scale surface melting of the Greenland ice sheet in 1889 and 2012. This contradicts conventional thinking that the melting was driven by warming alone.
The findings suggest that continued climate change will result in nearly annual widespread melting of the ice sheet’s surface by the year 2100. Melting in the dry snow region does not contribute to sea level rise. Instead, the meltwater percolates into the snowpack and refreezes, leaving a less reflective surface. This reformed surface becomes even more susceptible to future melting due to the surface’s reduced reflectance. The ability to reflect sunlight is known as “albedo.”
The study, conducted by Thayer School of Engineering and the Desert Research Institute, is reported in the Proceedings of the National Academy of Sciences. The research was supported by the National Science Foundation and NASA.
“The widespread melting of the Greenland ice sheet required the combination of both of these effects—a lowered snow albedo from ash and unusually warm temperatures—to push the ice sheet over the threshold,” says Kaitlin Keegan, the study’s lead author and a Dartmouth doctoral student. “With both the frequency of forest fires and warmer temperatures predicted to increase with climate change, widespread melt events are likely to happen much more frequently in the future.”
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photo by Laura Levy