North’s melting glaciers may be carbon sinks

A glacier and mountains on Ellesmere Island.
Photo: Ruben Ramos/iStock/Getty Images

We all expect that an accelerated melting rate for Canada’s glaciers will cost us in ways we don’t even fully grasp yet — but for somewhat of an upside, it’s possible the waterways fed by those glaciers can help pull significant carbon dioxide (CO2) out of the air.

University of Alberta biologists have been studying the Lake Hazen watershed in Quttinirpaaq National Park on Nunavut’s Ellesmere Island to gauge the impact of melting glaciers on freshwater systems.

As the research team said in their paper in the Proceedings of the National Academy of Sciences, glacier melt is “one of the most dramatic consequences of climate change in high-latitude and high-altitude environments.”

But as those meltwaters move across “poorly consolidated” landscapes, they’re carrying “vast quantities of highly reactive comminuted sediments, prone to chemical weathering reactions that may consume atmospheric CO2.”

“Chemical weathering” refers to a series of chemical reactions that happen as rocks, sediment, soil and other such materials make contact with water and gases from the atmosphere.

The big difference between glacier-fed water bodies and those found in “nonglacierized” catchments is that the glacier-fed waters get relatively little organic matter coming in to decompose and produce CO2.

Rather, the team said, the glacier-fed waterways carry “easily mobilized comminuted sediments available for carbonate and silicate weathering reactions.”

“We observed that concentrations of carbon dioxide in the rivers were much lower than in the atmosphere, meaning that rivers are actively consuming carbon dioxide from the atmosphere,” PhD student Kyra St. Pierre, who ran the study under supervision of professor Vincent St. Louis, said in a U of A release.

The team used a “whole watershed approach” in the Arctic, along with measurements of dissolved CO2 in glacial rivers in Greenland and in Canada’s Rockies, to show certain glacier-fed freshwater systems are “significant and previously unrecognized annual CO2 sinks due to chemical weathering.”

Given that many of the world’s rivers flow from glacial headwaters, this process could be important for “contemporary regional carbon budgets” in those watersheds.

In Nunavut’s Lake Hazen watershed, for instance, the U of A team found weathering reactions in the rivers “actively consumed” carbon dioxide up to 42 km downstream of glaciers.

“We suggest that CO2 consumption in proglacial freshwaters due to glacial melt-enhanced weathering is likely a globally relevant phenomenon, with potentially important implications for regional annual carbon budgets in glacierized watersheds,” the team wrote.