May 20 2015, 9pm in Alaska, tune in to KAKM Science Wednesdays, Alaska Public Media, for Frontier Scientists’ CHANGING PERMAFROST.
Under the tundra thawing Permafrost forms thermokarst features, causing sinkholes and landslides. Shifting climate conditions release greenhouse gases locked beneath the tundra in previously frozen ground. The episode features University of Alaska Fairbanks Geophysical Institute scientists. Catch clips online at https://frontierscientists.com/projects/permafrost/.
Vladimir Romanovsky is a geophysicist and a professor in the Department of Geology and Geophysics at the University of Alaska Fairbanks Geophysical Institute. He explained: any earth material below ground which remains at or below 0 degrees Celsius [32 degrees F] for two or more years consecutively is permafrost. Most permafrost soil is composed of layers of ancient dead vegetation. That means permafrost is carbon-rich.
In permafrost across the globe, “Estimates (which were made lately) of carbon in permafrost show that right now in the upper 3 meters there is more carbon- twice [as much] carbon- in frozen state than is in the atmosphere,” Romanovsky told FrontierScientists. He added, it “Probably will not happen any time very soon,” but if it were released, “The amount of carbon in atmosphere could be tripled.” That’s a problem because when carbon locked away in frozen permafrost ground thaws it’s able to enter the atmosphere as carbon dioxide (CO2) or methane (CH4), both powerful greenhouse gasses which contribute to global warming. Estimates put the amount of carbon in permafrost at about 1,400 – 1,600 gigatons.
On the Arctic plain permafrost features march across the landscape with a strange alien geometry. The sight is mesmerizing when viewed from above, like the back of an immense beast. These patterns are formed by ice wedges where water has infiltrated cracks in the ground then frozen. The expanding ice pushes away surrounding soils until they approximate a ring. Encased in the ring are the ice wedges; melt water collects atop them, helping to form a shining legion of shallow lakes. The formations help define the ecosystem of the far north.
Yet trends are changing. Romanovsky stated you can see an “Interaction between more open waters during the summer and degradation of permafrost in coastal sites.” When summer sea ice is less present in Arctic waters it means a warmer ocean, warmer air temperatures, and increased precipitation. In the Arctic that might mean more rain which infiltrates and degrades permafrost. Alternately it might mean more snow which serves as insulation, keeping the ground protected from cold winds. Romanovsky explained “If you have more snow, generally, permafrost is warmer and much less stable. The degradation of permafrost could happen easier.” He added: “Of course the whole Arctic system will change with changes in ice distribution and that will affect permafrost as well.”
Ice and fire
The layer of permafrost on the Alaskan Arctic Plain measures up to 650 meters [2,132 feet] thick.
In reliable cold underground ice provides strong building blocks for permafrost. Yet in warming temperatures, permafrost containing a significant amount of ice can experience rapid disintegration when ice melts. Sinkholes and landslides form when ice melt makes the ground slump. Water changing into ice and back causes frost heaves to make the ground move up and down, breathing through the years. Coastal communities built on permafrost ground have to guard against erosion, and buildings like Fairbanks resident Ruth Macchioni’s house tilt on unevenly settling ground.
“To completely thaw permafrost even in interior Alaska it will take hundreds and hundreds of years,” Romanovsy said. “However, most of the organic material and the carbon is sequestered in the upper part of permafrost.” Fire is a concern. “After [a] good forest fire permafrost thaws down to 3 or 4 meters. Even if it’s just 3 or 4 meters it’s already [having a] huge impact on infrastructure and on ecosystem and on carbon cycle. So we don’t need to wait until all permafrost will be gone to have an effect. Effect will happen actually immediately after permafrost starts to degrade.” Warming temperatures, heightened precipitation, and even wildfire challenge the stability of permafrost ground and free permafrost carbon into the global carbon cycle.
Romanovsky: “One one side permafrost will not disappear any time soon so our job is pretty secure. On another side any active degradation of permafrost even from the very beginning will have impact.”
Romanovsky and colleague Sergey Marchenko visit a data logger in the forest. The data logger is hidden by moss to avoid notice from curious animals. They uncover it and connect a cord to download the data. The logger is contained in a small electronic casing with temperature sensor wires extending underground via a hole bored into the ground. The sensor measures temperatures at the surface and at varying depths below, recording measurements at one hour intervals. This one has been recording for two years.
The data is used to create supercomputer-driven permafrost simulations, or models. The models allow researchers to form more complete climate predictions, helping shape responses. Marchenko showed a model depicting permafrost conditions, then fast-forwarded to the future (2020-2029) when the mean annual temperature of permafrost at 2 meters depth is forecasted above freezing for much of southwest Alaska.
Models help researchers forecast the future of permafrost, and see how vulnerable the carbon sequestered (locked away) in permafrost is to being released into the global carbon cycle. How much permafrost carbon will eventually end up as atmospheric CO2?
Laura Nielsen 2015
Frontier Scientists: presenting scientific discovery in the Arctic and beyond