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​Melting glaciers dump carbon into the sea

Several recent reports have found that glaciers are melting faster than scientists realized and that as a result, sea levels are rising faster than ever before. Now, new research sheds light on another aspect of the global melting trend.

In addition to adding water to the oceans, eroding ice sheets are also contributing significant amounts of carbon that feed the bottom of the food chain in marine ecosystems. The findings raise a new question: What will happen to these ecosystems when the glaciers melt away?

"This is the first attempt to figure out how much organic carbon is in those glaciers and how much will be released when they melt," said Robert Spencer of Florida State University, one of the authors of a study out Monday in Nature Geoscience looking at the impact of this release.

Glaciers, far from being just massive blocks of frozen fresh water, contain their own natural stores of organic carbon, and also amass the element from the accumulation of soot or from other outside sources. By analyzing measurements of organic carbon in glaciers and ice sheets around the world, the research team found that when the glaciers melt, large amounts of pent up carbon are released into local waters. They estimate that the release will increase by 50 percent over the next 35 years, as glaciers and ice sheets continue to melt at a rapid pace.

"Naturally as glaciers melt there may be a short-term increase in the flux of organic carbon into marine ecosystems but that will of course decline as glaciers continue to shrink," Spencer told CBS News. "It's a short term increase for a very long term loss."

The problem is that scientists don't know what will happen when this carbon contribution is removed from the equation. Microbes at the bottom of the food web can thrive on glacier-derived organic carbon. If their supplies run low as global ice stores melt into oblivion, it could affect entire ecosystems from the bottom up.

"It could change the whole food web," Spencer said.

He and his collaborators will continue to study the impact of glacial carbon runoff. "The thing people have to think about is what this means for the Earth system," he said. "We know we're losing glaciers, but what does that mean for marine life, fisheries, things downstream that we care about?"

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