Sleeping Giants

New research shows we may have been single-minded in our thinking about the consequences of glacial melting. Sure, sea-level rise is worrying, but we also need to pay attention to the carbon that will be released by all that melting ice.

A recent Nature Geoscience paper offers the first-ever estimate for how much carbon the world’s glaciers will release when they melt. It also predicts how all that water-bound carbon will affect the rivers and coastal habitats it flows into. The researchers expect a 50 percent increase in the carbon footprint of glaciers over the next 35 years. That’s a total of 15 trillion grams of dissolved carbon—half the amount that runs through the Amazon River each year—being released into the oceans.

Carbon occurs naturally inside glaciers, and also accumulates as airborne fossil-fuel pollution, like soot, settles on the ice over time. The researchers based their predictions on the amount of carbon that’s already been released from global glaciers and ice sheets—data that took them several years to gather. They also consider how all this extra organic content might affect aquatic ecosystems.

In a press release, Robert Spencer, an author on the paper and an oceanographer at Florida State University, said, “It could change the whole food web. We do not know how different ecological systems will react to a new influx of carbon.”

He speculates that initially, microorganisms at the base of the food chain will probably thrive, as glacial melt will provide them with a carbon banquet. “The effect cascades up the food web, to insect larvae, then fish, then birds, and so on,” Spencer tells Newsweek.

But that feast will soon turn into a fast. The feeding frenzy will slow when the flood of carbon dries up—an inevitability as glaciers continue to melt away. The sudden lack of carbon will cause organisms at the base of the crowded food chain, and everything above them, to suffer.

“It could be a double-edged sword. [When] glaciers decline, they are not coming back,” Spencer says.