Pan-Arctic ice-wedge degradation in warming permafrost and its influence on tundra hydrology

Liljedahl and her co-authors gathered information about the types of ice wedge polygons and how they changed over time across the Arctic. Although these regions contain “cold permafrost,” with an overall average temperature of roughly minus 14 degrees Celsius, surface thawing still occurred at all of the 10 study sites with nine of them presenting ice wedge degradation across the landscape. This is the first study to determine that ice wedge melting is widespread across the Pan-Arctic on sub-decadal time scales. Melting of the tops of ice wedges leads to ground subsidence around the polygons, which in turn allows drainage of polygon center ponds.  This succession of polygon type (from a pond at the center to a vegetated center mound) can create a connective drainage system that encourages runoff, even doubling it, and therefore leads to an overall drying of the landscape even if the amount of precipitation remains the same. The change in snow distribution is key as suddenly a majority of the snow is accumulated in these newly formed channels. Instead of being absorbed by the tundra, the snowmelt water will run-off into lakes and larger rivers. Gradual warming of permafrost has been well-documented in the Arctic, but the polygon study indicates that a brief period of unusual warmth can cause a rapid shift in a short time period.