Greenland Ice Sheet is Melting from Above and Below: Warming Impact

First Posted: Aug 12, 2013 11:53 AM EDT

It's not surprising that the Greenland ice sheet is melting. After all, scientists have known for quite some time that warmer temperatures are contributing to its decline. What is surprising, though, is the fact that this ice isn't only melting from the surface; it's also melting from below. Scientists have discovered that the high heat flow from the mantle into the lithosphere is helping the ice to melt.

The Greenland ice sheet plays a critical role in regulating climate. The white ice reflects sunlight back into the atmosphere, effectively cooling the planet. Unfortunately, this ice sheet is quickly melting. In fact, researchers estimate that it loses about 227 gigatons of ice per year and contributes about .7 millimeters to the currently observed mean sea level rise of about 3 mm per year. That's quite a big impact on the Earth's climate.

Yet air temperature alone doesn't explain the current rate of melting. That's why scientists took a closer look. Using computer models, the researchers combined an ice/climate model with a thermo-mechanical model for the Greenland lithosphere. This allowed them to see the combined effects of warming on the ice sheet. In all, the scientists ran the model over a simulated period of three million years, taking into account measurements from ice cores and independent magnetic and seismic data. They found that the model calculations were in good agreement with measurements from the environment.

"The temperature at the base of the ice, and therefore the current dynamics of the Greenland ice sheet is the result of the interaction between the heat flow from the Earths' interior and the temperature changes associated with glacial cycles," said Irina Rogozhina, one of the researchers, in a news release. "We found areas where the ice melts at the base next to other areas where the base is extremely cold."

The findings reveal a little bit more about how the ice sheet is melting. In addition, it could allow scientists to create more accurate climate models. This could help them better predict temperature fluctuations in the future and better allow them to assess the impact of global warming.

The findings are published in the journal Nature Geoscience.

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