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A Previously Undiscovered (Cold) Carbon Sink Comes To Light

What’s happening? Rivers formed of meltwater from High Arctic Canadian glaciers have been removing CO2 from the atmosphere at a quicker rate than the Amazon rainforest for decades, according to new research.

Why does this matter? This surprise discovery from Canadian and US scientists has shone light on a previously overlooked ecosystem service from the Earth’s cryospheric (frozen) systems – the absorption of CO2.

Traditionally, rivers in temperate regions have been viewed as emitters of carbon due to the decomposition of contained organic material, such as fish and plants. Glacial rivers, however, support less aquatic life, resulting in less organic decay and fewer carbon outputs.

But, critically, chemical weathering of glacial sediments in the meltwater, including carbonate and silicate, actually draws CO2 down from the atmosphere. This process was observed to continue up to 42 km downstream from glacial termini, leading the researchers to conclude CO2 absorption in glacial meltwater is a “globally relevant phenomenon”.

Amazingly, per square metre, glacial rivers are up to 40 times more effective than the Amazon rainforest at absorbing CO2; however, the Amazon covers a larger area of 6.7 million sq km so, as a system, absorbs more carbon.

Mountain glaciers around the world are retreating at an unprecedented rate due to climate change. The two largest bodies of ice, the Greenland and Antarctic ice sheets, are also melting faster than expected, partly due to newly discovered ice melting mechanisms. This has implications for sea level rise, as well as mountain water supplies.

On top of these impacts, the study gives yet another reason to curb climate change to protect the cryosphere. From a carbon sequestration perspective, as well as looking after the Earth’s “lungs”, we should also be looking after its icy areas.

A further thought from Curation – Despite being a fascinating revelation, unfortunately the meltwater sequestration mechanism is not enough to offset greenhouse gas emissions from other changes in the high and low Arctic, for example from melting permafrost. This too is an area where new science is shedding light on the carbon cycle, albeit with a much less positive message.

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Nick Finegold is Founder & CEO of Curation Corp, an emerging and peripheral risks monitoring service.