What is permafrost?

A new scientific study on thawing permafrost in the Mackenzie Delta in Northern Canada shows the phenomenon could lead to rising methane emissions both from natural production of the gas and the release of escaping subsurface fossil fuels.

The authors (of a study in the journal Scientific Reports) concluded that melting permafrost soils in the Arctic contributes to a warming climate in two ways, naturally producing more methane gas at the surface, and the thawing subsurface allowing geologically old methane to escape into the atmosphere.

Climate change triggers both natural production of the gas and stronger greenhouse gas emissions in the 10,000-square-kilometer area of the Delta. Scientists have warned that the effect of permafrost thawing and increased methane emissions could foster and accelerate catastrophic changes in climate, according to Courthousenews.com.

Permafrost is defined as ground (soil or rock and included ice or organic material) that remains at or below 0°C for at least two consecutive years. Lowland permafrost regions are traditionally divided into several zones based on estimated geographic continuity in the landscape. A typical classification recognizes continuous permafrost (underlying 90-100% of the landscape); discontinuous permafrost (50-90%); and sporadic permafrost (0-50%).

In the Northern Hemisphere, regions in which permafrost occurs occupy approximately 25% (23 million km²) of the land area. In the discontinuous and sporadic zones permafrost distribution is complex and patchy, and permafrost-free terrain is common. The thickness of permafrost varies from less than one meter to more than 1500 meters. Most of the permafrost existing today formed during cold glacial periods, and has persisted through warmer interglacial periods, states arcticportal.org.

Permafrost soils are extremely rich in organic carbon. According to one estimate they contain about 1700 billion tonnes of it – about twice the total amount of carbon currently in the atmosphere. When the soil remains deep-frozen, the carbon is largely inert, but when the permafrost thaws, the decomposition of organic matter through microbial activity increases sharply – with the consequence that large amounts of carbon will eventually get respired into the atmosphere as CO2 and (to a lesser extent) methane.

This is an example of a positive feedback loop, because the greenhouse gases released by the thawing permafrost will exacerbate the warming, leading to more permafrost thawing, more warming, and so on, writes www.theguardian.com.