Permafrost is any rock or soil material that has remained below 0°C Centigrade continuously for 2 years or more. This can range in depth from a few metres to one kilometre deep and underlies 12-18% of the exposed land surface in the Northern Hemisphere and to a lesser extent in the Southern Hemisphere.
There is now evidence that permafrost has shown a significant warming trend during the last 30 years and is melting due to climate change, at some sites long-term degradation has already started.
Although widespread changes to permafrost usually take centuries, the Intergovernmental Panel on Climate Change (IPCC) estimates that by the mid-21st century, the area of permafrost in the northern hemisphere will decline by 20-35%. Additionally, the United Nations Environmental Programme suggests the depth of thawing could increase by 30-50% by the year 2080.
The ground in areas with permafrost is normally suitable for buildings and other structures, however as it melts it reduces the ability of the ground to support heavy constructions:
a) Recently in Norris and Yakutsk, Russia, more than 500 tall buildings have been significantly damaged.
b) Similarly damage is affecting roads and pipelines.
In some areas surface travel is possible only when the ground is frozen solid, but as the permafrost melts so this times reduces. In fact, over the last 30 years in some areas the number of days vehicles can use perma-roads each year has reduced from 225, to less than 25 days per year.
For thousands of years permafrost has worked as a carbon sink, because dead vegetation does not rot but is stored in the ground. Warming of the permafrost allows micro-organisms to break down the biological material. In this process, methane and carbon dioxide are released.
The carbon is mostly released as methane, because the rotting process is happening in wet soil with little or no supply of oxygen. Frighteningly methane as a greenhouse gas is about 21 times more potent than CO₂.
It is thought upper layers of permafrost contain more organic carbon than is currently contained in the atmosphere. Massive volumes could be released by the end of the century.
This could be an irreversible cycle, the recent increase of world temperature of 1°C has started the permafrost melt, this allows the release of vast volumes of Green House gases which will contribute to global warming and speed up the temperature increase, which means faster melting and faster release of Methane and so on and so on.
We understand that currently, climate models do not incorporate the effects of methane released from melting permafrost, which means even the most extreme warming scenarios we’ve come up with might not be extreme enough. A spike in atmospheric methane concentration could set off catastrophic global warming.« Algal blooms | London exceeds pollution limits in just 8 days »