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article imageMineral weathering and permafrost carbon dioxide release

By Karen Graham     Sep 20, 2018 in Science
Alberta - The amount of carbon dioxide released from thawing permafrost might be greater than previously thought because of a process called mineral weathering, according to a new study by University of Alberta ecologists.
The research is the first to document the potential for substantial contributions of CO2 from thawing permafrost to the atmosphere through an inorganic process called mineral weathering, according to the University of Alberta.
Frozen permafrost can transform vast stores of organic carbon into carbon dioxide when the permafrost thaws, and of course, this is a serious concern. But the potential counterbalance from CO2 fixation through chemical weathering of minerals exposed by thawing permafrost has never been studied, say the researchers.
Permafrost is rich in minerals that are released when the ice melts. It is then that the minerals become vulnerable to a process called chemical weathering.
Chemical weathering occurs when rocks undergo chemical reactions to form new minerals. Water, acids, and oxygen are just a few of the chemicals that lead to geological change. Over time, chemical weathering can produce dramatic results.
In this type of weathering, sulfuric or carbonic acid that can exist naturally in water, break down the minerals in the exposed rock into their mineral components. Interestingly, over long periods of geologic time, carbonic acid weathering has been an important control on atmospheric CO2 levels and climate.
However, under certain conditions, weathering by sulfuric acid can release quite a lot of carbon dioxide - and researchers from the Department of Biological Sciences have shown that these conditions are prevalent in the western Canadian Arctic, and are being enhanced by permafrost thaw.
Warming permafrost softens coastlines  making it more vulnerable to wave action and promoting erosio...
Warming permafrost softens coastlines, making it more vulnerable to wave action and promoting erosion along the Arctic coast of Alaska. A large block of ice-rich permafrost has detached from the mainland and will quickly disintegrate (photo: Christopher Arp).
United Nations Environment Programme
To understand the regional impacts of permafrost thaw and weathering, Ph.D. candidate Scott Zolkos and his supervisor Suzanne Tank, assistant professor of biology at U of A, worked with scientists from the Northwest Territories Geoscience Office to examine long-term records of river chemistry from the Peel River.
"We found that rapidly thawing permafrost on the Peel Plateau in the Northwest Territories is greatly enhancing mineral weathering," explained Zolkos, the lead author on the study. "Because weathering is largely driven by sulfuric acid in this region, intensifying permafrost thaw could be an additional source of CO2 to the atmosphere."
Example of a karstic hole with fresh water - even in summer.
Example of a karstic hole with fresh water - even in summer.
On land, melting permafrost is shaping new landscapes through a process called thermokarst — a term for thawing-driven erosion that originated in Russia, according to the U.S. Geological Survey (USGS).
And as the thawing of the permafrost continues, and more thermokarst activity is being documented, sulfide-rich regions will continue to transfer CO2 to the atmosphere. However, how this will balance out with those regions where carbonic acid is produced during thawing is still a big unknown.
This very interesting study was published in the journal Geophysical Research Letters on September 5, 2018.
More about Permafrost, Carbon dioxide, sulfide oxidation, thermokarst, weathering
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