Full-tilt chaos has descended on the Arctic, a region that’s now warming twice as fast as the rest of the planet. This summer it’s been sweltering under unprecedented heat, and wildfires have so far consumed 2.4 million acres in Alaska alone, releasing massive amounts of carbon dioxide. It’s so hot up there that thunderstorms, more often seen in tropical climes, are striking near the North Pole.
Add to this bizarro affair a strange, perhaps counterintuitive finding in the far north of Canada, right next to Greenland. Researchers have found that watersheds fed by melting glaciers are actually soaking up a significant amount of carbon dioxide, in contrast to your typical river, which emits carbon dioxide. On average during the 2015 melting season, per square meter (to be clear, not in total) these glacial rivers consumed twice as much CO2 as the Amazon rainforest. So ironically enough, glaciers melting under the weight of global warming can help sequester carbon, making such watersheds a previously unrecognized CO2 sink.
If you were looking for a way out of our impending climate doom, however, this ain’t it. For one, the sequestering powers of glacial meltwater can’t keep up with our out-of-control emissions, or even other climate change-induced emissions from the Arctic like melting permafrost. And if we keep melting glaciers, we’ll run out of meltwater too. Still, the findings are a key piece in understanding the monumentally complex carbon cycle on this planet.
Glacial rivers are very different from rivers elsewhere in the world. One striking difference is they’re largely abiotic—algae and fish typically don’t colonize them because they’re just too cold. So instead of being chock-full of life, they’re chock-full of sediment.
Matt Simon covers cannabis, robots, and climate science for WIRED.
“As these glaciers are retreating or advancing, which they do every year, they’re actually forming a lot of very fine sediments that are just wide open on the landscape,” says Kyra A. St. Pierre, a biogeochemist at the University of British Columbia and lead author on a new paper describing the findings. Glacial meltwaters pick up this sediment, making them mineral-rich. These rivers of meltwater then gather in mineral-rich glacial lakes.
The thing about carbon dioxide is that it flows freely across the surface of water—the water can both absorb the gas and give it off. In a typical river, organisms are consuming organic material and giving off CO2, or respirating, just like humans do. Thus the river becomes a net carbon producer, because it’s saturated with so much CO2 that the water just can’t dissolve any more CO2 from the air. Same goes for ponds and lakes the world over—they’re greenhouse gas emitters.
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