Permafrost is frozen ground - a mixture of soil, rock, sand, and ice - that remains at or below 0°C for at least two consecutive years. Permafrost covers about a quarter of the landmass in the Northern Hemisphere, the majority of which can be found in northern Russia, Canada, Alaska, Iceland, and Scandinavia. As long as it stays frozen, it’s no threat to the climate.
But rising temperatures have driven widespread permafrost thaw since the late 20th century, with the rate accelerating in recent decades.
To better understand the impacts of permafrost thaw, researchers at the University of Massachusetts Amherst analyzed a Wisconsin-sized area of Alaska’s North Slope, where rivers drain into the Beaufort Sea. Using 44 years of high-resolution data, they found that the thaw season is lasting longer, river runoff is increasing, and more previously frozen carbon is being transported from land to sea.
This increase in freshwater can disrupt ocean systems by interfering with sea ice formation, changing the salinity of coastal waters, and transporting carbon that can later be released into the atmosphere.
The study, which was recently published in the journal Global Biogeochemical Cycles, also found that as temperatures rise, the soil’s “active layer” (which freezes and thaws each year) is getting deeper. This allows more groundwater to flow into rivers and releases ancient organic material that had been frozen for thousands of years.
These findings may help researchers better understand the far-reaching impacts of thawing permafrost across the Arctic, a region warming about three times faster than the rest of the planet.
