Researchers have discovered that the weathering of rocks in the Canadian Arctic is set to speed up as temperatures rise, generating a positive feedback loop that will result in the continual release of carbon dioxide (CO2) into the atmosphere.
A team from the Department of Earth Sciences at the University of Oxford has revealed that increasing temperatures will accelerate the weathering processes of Arctic rocks, intensifying a cycle that could release more CO2 into the air. Their findings are published today in the journal Science Advances.
Understanding how weathering contributes to atmospheric CO2 is especially important in the Arctic, where air temperatures are rising nearly four times faster than the global average. Some minerals and rocks react with atmospheric oxygen, leading to chemical reactions that release CO2. A prime example is the weathering of sulfide minerals (like ‘fool’s gold’), which produces acid that releases CO2 from nearby rock minerals. As permafrost in the Arctic thaws due to higher temperatures, these minerals are exposed, potentially accelerating climate change through this feedback mechanism.
Until now, it has been largely unclear how temperature changes affect these reactions and the amount of CO2 released.
In this study, the researchers analyzed sulfate (SO42-) concentration and temperature data from 23 sites in the Mackenzie River Basin, the largest river system in Canada, to assess how sensitive the weathering process is to increasing temperatures. Similar to CO2, sulfate is produced through sulfide weathering and serves as an indicator of the speed of this process.
The findings showed that sulfate concentrations across the basin increased sharply with rising temperatures. Between 1960 and 2020, sulfide weathering rose by 45% as temperatures climbed by 2.3oC. This suggests that the CO2 released from weathering could contribute to a feedback loop, intensifying warming in Arctic areas.
Based on these river records, the researchers estimate that CO2 emissions from the Mackenzie River Basin could double to 3 billion kg per year by 2100 under a moderate emissions scenario. This increase would be roughly equivalent to half the annual emissions from Canada’s domestic aviation sector in a typical year.
Dr. Ella Walsh, the lead author of the study and formerly of the Department of Earth Sciences at the University of Oxford, stated: “We observe significant increases in sulfide oxidation across the Mackenzie with even moderate warming. The temperature sensitivity of CO2 release from sulfide rocks and its primary influencing factors have not been well understood across large areas and timescales until now.”
However, not all regions of the river basin reacted uniformly. Weathering was notably more responsive to temperature changes in rocky, mountainous areas and regions covered by permafrost. Through modeling, the researchers found that the process of freezing and expanding further accelerated sulfide weathering.
In contrast, regions with peatland experienced smaller increases in sulfide oxidation as the peat layer helps protect the bedrock from weathering.
Co-author Professor Bob Hilton from the Department of Earth Sciences at the University of Oxford remarked: “As temperatures continue to rise across vast Arctic landscapes, sulfide oxidation rates may further increase and impact regional carbon cycle budgets. With this information, we are now focusing on understanding how to mitigate these reactions, and it appears that the formation of peatlands could be beneficial in slowing sulfide oxidation.”
Many similar environments exist in the Arctic, where the combination of different rock types, large areas of exposed bedrock, and extensive permafrost create conditions for rapid increases in sulfide weathering as warming occurs. This suggests that the effects observed in the Mackenzie River Basin may be widespread.
The researchers emphasize that this study underscores the importance of incorporating sulfide weathering into large-scale emissions models, which are critical for forecasting climate change.
Note:
*Data were obtained from Environment Canada through their National Long-term Water Quality Monitoring Programme. Sulfate concentrations were measured via ion chromatography, a method where liquid samples flow through a resin column that selectively attracts specific ions based on their charge.
