Melting of the permafrost in the Kolyma river basin


© Staffan Widstrand / Nature Picture Library


In the popular imagination, the thawing of Arctic ice is always associated with the melting of vast glaciers. This is only part of the story. This photo shows ponds of water formed by the thawing of permafrost, a frozen layer found just beneath the surface of the ground that covers approximately 25% of land in the northern hemisphere.
Permafrost traps vast amounts of carbon, methane, mercury and other substances that could irreversibly transform our world if dispersed into the environment.
Over the centuries, every winter, through the action of bacteria, the ground has absorbed the plants that flower during the Arctic summer. It is estimated that at least 1,460 billion tons of organic material are presently retained by in this way, corresponding to twice the amount of carbon currently in the atmosphere. As this carbon is released, though some of it goes to nourish new plants, a massive quantity, some 300-600 million tons a year, is dispersed into the atmosphere, turning the Arctic region into an immense greenhouse gas factory. It is also believed that the permafrost forms the world’s largest reserve of mercury and other heavy metals. The risk of the water supply becoming contaminated is therefore extremely high.
The thawing of the permafrost is one of the most serious phenomena coincident with rising temperatures. It might not only accelerate global warming, but even make it self-fuelling and insensitive to whatever actions mankind might attempt to stop it. This stratum of frozen ground prevents the release of three billion tons of methane, a greenhouse gas twenty times more potent than carbon dioxide in its impact on the environment.

Alberto Claudio Alvisi