A geological time bomb is ticking beneath the Arctic ice — one that could be triggered by rapidly rising temperatures. The North is heating up twice as fast as the rest of the globe and has reached a threshold of warming that is unmatched in modern times. As a result, permafrost, the frozen soil and rock that covers about 25 percent of the land in the northern hemisphere, and 40 to 50 per cent of the land area in Canada, is beginning to thaw.
In fact, permafrost soils are warming even faster than Arctic air temperatures. Studies done by the Arctic Council indicate that the permafrost has warmed by two degrees Celsius in the last 30 years and that 20 per cent of it may thaw by 2040.
Warming permafrost poses numerous problems. Not only does it weaken the ground, creating cracks and craters and playing havoc with infrastructure, it can also affect regional ecosystems, altering the chemistry and flow of water and what types of plant and animal life can thrive in an area. Most alarming of all, a huge cache of greenhouse gases that has been frozen for thousands of years could be released by the thaw.
“We know there is twice as much carbon locked up in permafrost as there is carbon dioxide in the atmosphere,” says Suzanne Tank, a professor of biological sciences at the University of Alberta. “So certainly, there is the potential for this carbon, if it’s released as carbon dioxide, to have a really huge effect on greenhouse gases and climate warming.”
The release of heat-trapping gases accelerates global warming, which in turn causes more thawing. The great fear is that this self-reinforcing cycle could eventually create a calamitous “tipping point,” at which the cycle of warming permafrost will be impossible to stop.
Here’s a look at seven possible outcomes of thawing permafrost that have scientists concerned.
As Arctic permafrost warms, the ground grows mushier. Roads and buildings constructed on once-solid ground are now exhibiting signs of settling and cracking. In Norilsk, a Siberian mining town located north of the Arctic Circle, melting permafrost has deformed an incredible 60 per cent of existing buildings. In addition to such slow-moving wrecks, there are other areas in the Arctic where the land has completely collapsed, producing massive craters and thermokarst lakes, formed when ice-rich permafrost melts.
Rising temperatures are known to spur carbon release, but many experts now believe that changes in soil moisture conditions from wet to dry are apt to have an even stronger impact on permafrost carbon feedback. The danger was vividly illustrated in 2007 when a section of Alaskan permafrost caught fire and smoldered for several weeks. Covering some 90,000 hectares, the Anaktuvuk River fire was the largest recorded on treeless Arctic tundra and twice the size of all previous Alaska tundra fires combined. According to a 2011 article in Nature, the fire spewed as much carbon into the atmosphere as the tundra had stored in the previous 50 years.
The globe’s permafrost contains an estimated 1,500 billion tons of carbon. That is four times the amount of carbon that has been released into the atmosphere from all fossil-fuel combustion and human activities since 1850. At present, the majority of northern ecosystems take in more carbon than they emit. But rising temperatures and drying caused by climate change will shift this balance, as much of this organic material is concentrated within three metres of the surface in thaw-vulnerable soil. A thicker, warmer and drier active layer will activate microbes during summer. Significantly later freeze-ups of this layer in winter and warmer winter temperatures will also enhance microbial activities. This enhanced process of decomposition will produce more heat and, in turn, more carbon dioxide.