In the turbid, frigid waters roaring from the glaciers of Canada's high Arctic, specialists have made an astonishing discovery: for quite a long time, the northern rivers covertly pulled carbon dioxide from the atmosphere at a rate faster than the Amazon rainforest.
The results, published in the Proceedings of the National Academy of Sciences, flip the conventional understanding of streams, which are greatly seen as sources of carbon emissions.
“It was a total surprise,” said Dr. Kyra St Pierre, a biologist at the University of British Columbia and lead researcher on the project. “Given what we know about the rivers though … the findings are intuitive when you think about it. But we were initially very surprised to see what we did.”
The discovery originated from time spent gathering meltwater samples on Ellesmere Island, in Canada's Nunavut territory, where a few glaciers flow into Lake Hazen. The group of analysts additionally accumulated samples in the Rocky Mountains and Greenland.
“We have a pretty good understanding of the state of glaciers globally,” said St Pierre. “One thing we don’t know much about is the meltwaters and what happens when it … flows into rivers and downstream lakes.”
In temperate rivers, an abundance of natural material – plant life and fish – leads to higher levels of decomposition, which means the bodies of water emit a far more prominent measure of carbon dioxide into the atmosphere than they retain.
Be that as it may, glacial rivers, with their milky appearance and silt-laden composition, are not truly friendly to oceanic life, leading to far less natural decay– and little carbon output.
Simultaneously, the fine sediment scraped from glaciers, including silicate and carbonate, when tossed along in the rushing waters, starts the geographical procedure known as chemical weathering.
"As the rivers take up the particles, they start to mix within the water and within that water, there are also gases, including carbon dioxide,” said St Pierre. “The mixing together creates these reactions and puts all these different particles together. That’s where we see that the net result is the sink of carbon dioxide.”
The exploration group found the impact of chemical weathering in removing carbon dioxide from the atmosphere reached out as far away as 26 miles (42km) from the headwaters of the river.
This implies during high dissolve periods, these river water will retain 40 times as much carbon as the Amazon rainforest.
“On a per-meter-squared basis, these rivers can consume a phenomenal amount of carbon dioxide,” said St Pierre. But their limited size means on a gross scale, they pull in far less than the sprawling Amazon. The team plans on sampling meltwaters in the Canadian Rockies and expect to find similar results.
In a rapidly changing climate, the findings provide a surprisingly optimistic message: there are often unseen or underappreciated ways in which the planet regulates carbon emissions. “It shows just how little we know about these systems,” said St Pierre.
In any case, the Vancouver-based biologist alerts that the short-term benefits of the newfound carbon sink also illustrate the fast decline of glaciers in northern Canada.
“Glaciers are a finite resource. The waters that emanate from them are also a finite resource. And we’re potentially losing something that we’re deriving a lot of benefits from before we fully understand it,” said St Pierre.
The past research into glacial retreat found that the huge bodies of ice and rock were shrinking at a rate far faster than at first expected by scientists.
Lake Hazen, the subject of St Pierre's exploration, additionally makes for an intriguing contextual investigation.
In research distributed a year ago in the journal Nature Communications, biologists found the lake, one of the biggest of the high Arctic, was changing at a dramatic rate. Since 2007, water entering the lake from melting glaciers has increased tenfold over historic flow rates. With the water comes sedimentation, similar particles responsible for removing carbon dioxide. Due to the cloudier water in the lake, specialists speculate that the single population is growing skinnier, with the fish thinking that it is harder to navigate the murky waters.
As warming in the Canadian Arctic accelerates at a rate faster than the remainder of the planet, St Pierre hopes that it isn't too late for the public to understand the stakes for the region.
“Within the context of climate change, we’re losing systems that are just spectacular for the people who get to see them,” said St Pierre. “And we hope that people see why this science is important.”