Newsweek: “As the world warms, glaciers around the world are rapidly hemorrhaging ice and threatening catastrophic sea level rise. But melting glaciers also pose another kind of menace: the release of vast amounts of stored organic carbon into waterways. Florida State University assistant professor Robert Spencer and his colleagues have spent nearly a decade researching this overlooked aspect of glacial melt. In a paper published Monday, the team presented the first-ever estimate of how much carbon is due to be unlocked as the glaciers disappear — and just how little is known about what that might mean for aquatic ecosystems and the fate of surrounding fisheries. By 2050, roughly 15 teragrams of dissolved organic carbon is due to be released into waterways from melting glaciers, the team estimates. For context, one teragram is a trillion grams, and fifteen teragrams is the equivalent of half the dissolved organic carbon that flows through the Amazon River each year. Put another way, it’s a whole lot.”

“Polar ice sheets and mountain glaciers, which cover roughly 11% of the Earth’s land surface, store organic carbon from local and distant sources and then release it to downstream environments. Climate-driven changes to glacier runoff are expected to be larger than climate impacts on other components of the hydrological cycle, and may represent an important flux of organic carbon. A compilation of published data on dissolved organic carbon from glaciers across five continents reveals that mountain and polar glaciers represent a quantitatively important store of organic carbon. The Antarctic Ice Sheet is the repository of most of the roughly 6 petagrams (Pg) of organic carbon stored in glacier ice, but the annual release of glacier organic carbon is dominated by mountain glaciers in the case of dissolved organic carbon and the Greenland Ice Sheet in the case of particulate organic carbon. Climate change contributes to these fluxes: approximately 13% of the annual flux of glacier dissolved organic carbon is a result of glacier mass loss. These losses are expected to accelerate, leading to a cumulative loss of roughly 15 teragrams (Tg) of glacial dissolved organic carbon by 2050 due to climate change — equivalent to about half of the annual flux of dissolved organic carbon from the Amazon River. Thus, glaciers constitute a key link between terrestrial and aquatic carbon fluxes, and will be of increasing importance in land-to-ocean fluxes of organic carbon in glacierized regions.” [Nature Geoscience (2015) doi:10.1038/ngeo2331]