Warming in northern areas: the new Greenland, really?
The temperature increase due to climate change is particularly sensitive at Earth’s poles. Significant impacts can therefore be expected in these regions that could seriously affect Northern countries. While temperature increase is sometimes seen as an opportunity to increase agricultural suitability in these regions, conjuring tales of Vikings discovering a pastoral Greenland, upsets could be much more pernicious. Effects on permafrost are particularly worrisome.
Permafrost is a solid layer of frozen soil that covers about one fifth of terrestrial land. Vast parts of arctic regions (most of Greenland and Alaska, half of Canada and the Russian Federation) are resting on this solid ground, which can be hundreds of meters deep. Permafrost can be continuous, discontinuous or sporadic. Only a thin layer temporarily thaws in summer, which is called the ‘active layer’. One of the direct effects of global warming is the progressive melting of permafrost. This has in turn multiple effects: on soils, on the hydrological cycle and the climate which appear heavily disrupted. Soil is severely degraded, especially in most northern regions where tundra bushes do not show good levels of resilience, compared to taiga landscapes in southern regions where trees are more abundant. The fast erosion of Arctic shoreline and riverbanks is also notable, due to the intensification of rainy periods that follow the withdrawal of the arctic ice sheet. These intense rainy periods lead to multiple floods in both inhabited areas and wild zones, where pastures can be submerged. One sees the appearance of swamps and what is called “drunken forests”: as the soil degrades, tree roots lose their grip on soil and forests sag. A similar phenomenon occurs in built areas, where infrastructure stability is threatened by ground weakening. Industrial infrastructure destabilization, in particular, may increase the occurrence of leaks and generate environmental pollution. Finally, an additional risk of permafrost melting is the possible reviving of frozen microbes, as recently observed in some regions, like in Siberia. Outbreaks so far have been quite easily controlled, however.
The consequences on climate dynamics are very significant as well, and they do not concern northern countries only. Permafrost contains large quantities of carbon, of which a part is vulnerable to release in the form of carbon dioxide (following the decomposition of newly defrosted organic matter) and methane (through bubbling out of lakes notably) and worsen climate change. Quantities of carbon in the permafrost are huge: about a third of Earth’s soil carbon is found in Arctic tundra soil, corresponding to twice as much as what is in the atmosphere, and four times the historical quantities emitted by human activity. These estimates have been revised upwards recently, as researchers realized that organic carbon was stored much deeper in frozen soils than the top meter of soil traditionally analysed in other regions. Not all this carbon is susceptible to discharge, however, and estimating the release fraction is one of the key questions for the scientific community at present. This is a very difficult task, however, as thawing processes are complex and measurements difficult to make in these extreme environments. An additional source of carbon emissions comes from tundra fires, which seem to be exacerbated by permafrost melting.
The IPCC estimates that by mid-21st century, the area of permafrost in the northern hemisphere will have declined by 20-35%. Such prospect as evidenced by current trends would augur more a muddy future than a new Greenland for these regions.
Hadrien Lantremange, Analyst
Source: Beyond Ratings