In AK & Arctic Canada, Warmer And Rainier Summers Speeding Permafrost Melt And Erosion
Longer, rainier summers are thawing permafrost at an accelerated rate in interior Alaska, according to a new study, begging the question: what does this mean for rainy summers in the Canadian North?
“Thawing is happening even faster than we thought,” said Thomas Douglas, an environmental engineer with the U.S. Army Cold Regions Research and Engineering Laboratory and lead author of the study. “We’ve had these crazy wet summers. It’s gonna be bad for permafrost.” The study, published in Nature’s Climate and Atmospheric Science journal, found that between 0.6 and 0.8 centimetres of permafrost thawed for every centimetre of above-average rainfall in Alaska between 2013 and 2017.
Many Yukoners likely noticed, and commented on, the many rainy summer days this year compared to last, but Fabrice Calmels, research chair of permafrost and geoscience at Yukon University Research Centre, said that’s a matter of public perception and doesn’t necessarily mean the territory’s permafrost cover was impacted. “We’ll have to check the precipitation record at the end [of the summer] to know the quantity of water that came to the ground,” he said. “There’s a difference between several large events and small events spread out through the summer.”
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Researchers looked at four permafrost sites near Fairbanks, Alaska, with differing types of vegetation cover such as grassy tundra, wetlands and mixed forests. They took measurements in the same locations every year throughout the study to monitor changes in the permafrost. Over the five years of the study, the depth of the active layer — the layer of soil above permafrost that freezes in the winter and thaws in the summer — increased to varying degrees across the sites, meaning the permafrost had started to thaw.
The summers of 2014 and 2016 were the first and third wettest seasons on record since meteorological data first started to be tracked in the area 91 years ago. The study shows this led to an increase in active layer depth. After the extremely wet summer of 2014, permafrost didn’t recover to 2013 levels, even after drier seasons that followed, the study shows. Several areas now have “taliks,” or pockets of earth surrounded by permafrost that no longer freeze up.
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https://thenarwhal.ca/climate-change-rain-arctic-permafrost-thaw/