Researchers at the University of Oxford have found that rising Arctic temperatures will speed up rock weathering, releasing more carbon dioxide and contributing to climate change. Their research suggests carbon dioxide emissions from the Mackenzie River Basin could double by 2100, highlighting the importance of incorporating sulfide weathering into climate models.
Researchers from the Department of Earth Sciences at the University of Oxford have shown that rising temperatures will accelerate rock weathering in the Canadian Arctic, creating a positive feedback loop that results in more and more carbon dioxide being released into the atmosphere. The research was published in Science Advances.
Understanding the potential contribution of atmospheric carbon dioxide from weathering is particularly important for sensitive regions like the Arctic, where surface air temperatures are warming nearly four times faster than the global average. One way is when certain minerals and rocks react with oxygen in the atmosphere, releasing carbon dioxide through a series of chemical reactions. For example, the weathering of sulfide minerals (such as "fool's gold") produces acids that cause other nearby rock minerals to release carbon dioxide. In Arctic permafrost, as temperatures rise and the ground thaws, these minerals are exposed, potentially becoming a positive feedback loop that accelerates climate change.
Until now, however, it was largely unknown how this reaction would respond to temperature changes and how much additional carbon dioxide would be released.
In the new study, researchers used sulfate (SO42-) concentration and temperature records from 23 sites in the Mackenzie River Basin, Canada's largest river system, to study the sensitivity of weathering processes to rising temperatures. Sulfate, like CO2, is a product of sulfide weathering and can be used to track how quickly this process occurs.
The results show that throughout the catchment, sulfate concentrations rise rapidly with increasing temperature. Over the past 60 years (from 1960 to 2020), sulphide weathering has increased by 45% as temperatures have increased by 2.3oC. This highlights that carbon dioxide released by weathering may trigger a positive feedback loop that accelerates warming in the Arctic.
Using past records from these rivers, researchers predict that CO2 releases from the Mackenzie River Basin could double to 3 billion kilograms per year by 2100 under a moderate emissions scenario. This change is equivalent to half of Canada’s domestic aviation industry’s total annual emissions in a typical year.
Lead author Dr Ella Walsh (Department of Earth Sciences, University of Oxford at the time of the study) said: "We found that sulphide oxidation increases dramatically across the Mackenzie region with even moderate warming. Until now, we have not known the temperature sensitivity of CO2 release from sulphide rocks and its main drivers over large scales and time scales."
Not all parts of the catchment react the same way. In rocky mountains and areas covered by permafrost, weathering is much more sensitive to temperature. By simulating this process, the researchers found that the fragmentation of rock as it freezes and breaks further accelerates sulfide weathering.
In contrast, areas covered by peatlands experience slower increases in sulfide oxidation as the climate warms because the peat protects the bedrock from this process.
Co-author Professor Bob Hilton (Department of Earth Sciences, University of Oxford) said: "Future climate warming across vast areas of the Arctic may further increase sulphide oxidation rates and impact regional carbon cycle budgets. Now that we have discovered this, we are working to understand how to slow these reactions, and the formation of peatlands appears to help reduce sulphide oxidation processes."
There are many similar environments across the Arctic, where rock types, high proportions of exposed bedrock, and large areas of permanently frozen ground combine to create conditions where a warming climate will lead to rapid increases in sulfide weathering. Therefore, it is highly likely that this impact is not limited to the Mackenzie River Basin.
The researchers believe this study highlights the value of accounting for sulfide weathering in large-scale emissions models that can be useful in predicting climate change.
Compiled from/SciTechDaily
DOI:10.1126/sciadv.adq4893