Melting Permafrost

Permafrost is ground which is frozen and remains below 0C for two years or more. It can be classified into three groups:

-          Continuous permafrost: underlying 90-100% of the landscape

-          Discontinuous permafrost: 50-90%

-          Sporadic permafrost: 0-50%

It underlies up to 25% of the Northern Hemisphere and the map below (taken from International Permafrost Association) shows where it can be found.

Recent changes in temperature due to global warming have meant that melting of permafrost has begun. In the Northern communities this has had a great impact, particularly on transport and infrastructure.

When permafrost begins to melt it does so from the top- down. The active layer (the layer which isn’t frozen at the top) becomes larger. This thickening of the active layer causes previously frozen plant material to decompose and release CO2 and methane into the atmosphere. Secondly, the ice in the upper part of the permafrost becomes water leading to the ground surface subsiding (US Arctic Research, 2003). When this happens in or next to a human settlement, structural integrity of buildings, roads and pipelines are threatened.

This is the problem currently being faced by many communities in the North of Canada. The Arctic town of Salluit is considering relocating to escape the melting permafrost. Their newly built fire-station has sunk into the ground only a year after its completion. The roads and foundations of buildings have begun crumbling (The Canadian Press, 2010) 

“Sara Brown, director of community operational support with the Northwest Territories Association of Communities, says the costs to upgrade and fix buildings in Canada's North could range from $250 million to $420 million.” (CBC News, 2011) 

In an attempt to combat the problem The Canadian Standards Association has published guidelines for infrastructure design in permafrost regions.