“Permafrost” and Thermokarst

     As temperatures rise in the arctic, “permafrost,” permanently frozen ground, is defrosting at an increased rate. 

     "However, permafrost isn't the only thing in the arctic that is disappearing. Exposed rock that was once covered in ice is dissolving, eaten away by acid. The effects of this acid bath could have far-reaching impacts on global climate, according to a new study.

     Icy permafrost is rich in minerals, which are released when the ice melts. The minerals then become vulnerable to chemical weathering, or the breakdown of rock through chemical reactions. Scientists investigated areas once covered by permafrost in the western Canadian arctic, finding evidence of weathering caused by sulfuric acid produced by sulfide minerals that were released when the permafrost melted.

     Another type of naturally occurring chemical erosion is caused by carbonic acid, and it also dissolves rock. But although carbonic-acid weathering locks carbon dioxide (CO2) in place, sulfuric-acid erosion releases CO2 into the atmosphere, and it does so in quantities that were not previously accounted for, researchers described.

      Dramatic changes are underway in the Arctic, which is warming about twice as fast as any other location on earth. Sea ice is rapidly dwindling, which reduces the ocean's heat-reflecting cover, accelerating the rise of ocean temperatures. And polar bears, which depend on sea-ice cover to hunt for seals, are losing their hunting grounds, and have a harder time finding enough to eat. 

     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).

     Thermokarst creates land formations such as lakes, pits, and sinkholes. It was not previously known how this process could affect weathering of exposed minerals, and how that might then impact CO2 release, according to the study.

     "These processes may influence the permafrost carbon-climate feedback, but have received little attention," the researchers reported.

     Over geologic time, weathering caused by carbonic acid can help to regulate climate, by trapping CO2 and restricting its transfer into the atmosphere. But the researchers found that thermokarst in regions that were rich in sulfides drove production of sulfuric acid, rather than carbonic acid, and thereby released quantities of CO2."

      These preliminary findings were published online 9/6/18 in the journal Geophysical Research Letters. (The "Plain Language" Abstract is something I've not seen before in professional journals; have you?)

       Thermokarst--easy enough for even kindergartners to understand, eh?
Steph










 


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