Figure 1: Component models - of varying complexity - in the "Permafrost Modeling Toolbox" (from EOS, Vol. 100, p. 33)
Figure 2: Computation of projected permafrost melting into the 2090s using CMIP5 to calculate relative steepening of permafrost active layer thickness (from EOS, Vol. 100, p. 33)
When last in Alaska, in March 2005, my wife and I got to see many sights including massive wilderness regions near Mount McKinley ('Denali") as well as immense glaciers in the southern region just below Anchorage. In the latter case, we were shown just how much glaciers had receded in just the last two decades.
On our dog sled trek near Chena Hot Springs, AK. We had to choose a path where the ice hadn't melted as rapidly as it had in other places.
Janice on her snowmobile near the Trans--Alaska pipeline. Melting permafrost had affected its stability - supports as well.
Meanwhile, during a visit to the Ice Art Exhibit in Fairbanks, several ice towers (including one 150' tall) collapsed due to melting permafrost beneath. When we visited the Geophysical Institute two days later, we were informed by one atmospheric physicist that "this is just the beginning, wait until homes, downtown buildings are affected."
Eight and a half years later the Nov. 26, 2013 issue of the peer-reviewed journal Nature Geoscience, featured a ground breaking paper by Natalie Shakhova and Igor Semiletov of the University of Alaska- Fairbanks' International Arctic Research Center. In the paper the authors warned that the Arctic Ocean is releasing methane at a rate more than twice what existing scientific models predicted. The two UAF researchers focused on the continental shelf off the northern coast of eastern Russia - the East Siberian Arctic Shelf. Underlying this region is sub -sea permafrost. When the permafrost melts, the methane (CH4 ) is released.
In an update (2017) of their earlier permafrost research,
Current rates and mechanisms of subsea permafrost degradation in ...
The authors actually showed the rate and mechanisms of subsea permafrost degradation and that it is a prerequisite to meaningful predictions of near-future methane (CH4 ) release in the Arctic.
While the gradual warming of permafrost has been well documented in the Arctic, another (2017) study published in Nature Geoscience indicated that a brief period of unusual warmth can cause a rapid shift. Focusing on the polygon ice troughs associated with wedges of ice that thrust deeply into the ground, the study found the ice wedges are quickly melting, amplifying the loss of permafrost by altering the storage and movement of water. The latter, of course, clearly shows the role of hydrology in permafrost dynamics.
It's an interesting kind of paradox: Climate change is currently thawing vast expanses of Arctic permafrost, and the effect is to release methane - an even more potent greenhouse gas than CO2. The released CH4 then goes into the atmosphere to accelerate climate change, further thawing permafrost and activating more methane release.
This is all serious research given that permafrost is hundreds of meters deep in many places and has been frozen for millennia. It covers approximately 24 percent of the Arctic and stores nearly 1,700 gigatons of organic carbon, far greater than the amount of carbon already in the atmosphere.
Ice-wedge degradation has been observed before, but this is the first study to determine that rapid melting of ground ice (as opposed tp sub-sea permafrost) has become widespread throughout the Arctic. The research team predicts that the melting—already occurring at sub-decadal timescales—will expand and intensify across the region, and this could escalate global warming and create more feedbacks.
All of which strongly demonstrates the need for more powerful, and accurate models of permafrost thawing, especially which show the various ways it thaws.
Currently, the ways that permafrost thaws is being investigated on multiple fronts given it is is interwoven with hydrological and geomorphological processes and how carbon and toxic heavy metals spread throughout the thawing Arctic. To be sure, we need more refined models and approaches given there remain are sweeping, yet unanswered, research questions..
To fix ideas first with basics, permafrost refers to ground that stays at or below 0°C for 2 or more years—can be found under 24% of the Northern Hemisphere’s land surface [Zhang et al., 1999]. The frozen subsurface profoundly influences the hydrological cycle of the Arctic region.
To address the issue of more refined models, climate scientists at the University of Colorado- Boulder have developed online, easily accessible permafrost process models for use by scientists and educators. This has been through the Community Surface Dynamics Modeling System (CSDMS) or the Permafrost Modeling Toolbox. (See Fig. 1)
The UC climate scientsts' "toolbox" includes three permafrost models of increasing complexity, all driven by local climate forcing, to meet a variety of needs: