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Alors que le pergélisol fond, il libère d'anciens virus, du carbone - et maintenant des déversements de carburant

JEAN-PHILIPPE CHOGNOT, AFP
7 JUIN 2020

La fonte du pergélisol, soupçonnée par la Russie d'être derrière un déversement de carburant sans précédent qui a pollué de vastes étendues de rivières arctiques, est une bombe à retardement menaçant la santé et l'environnement, et risque d'accélérer le réchauffement climatique.

On May 29, 21,000 tonnes of diesel fuel spilled from a reservoir that collapsed which Russian metals giant Norilsk Nickel owns through a subsidiary.

Norilsk, one of the country's biggest industrial centres, lies above the Arctic circle and Norilsk Nickel and Russian officials have said they had suspect permafrost thawing.

What is permafrost?

Permafrost - soil that is frozen - is found mostly in the Northern Hemisphere, where it covers about a quarter of exposed land and is generally thousands of years old.

It covers a wide belt between the Arctic Circle and boreal forests, spanning Alaska, Canada, and Russia.

It can vary in depth from a few metres to hundreds.

Locked into the permafrost is an estimated 1.7 trillion tonnes of carbon in the form of frozen organic matter - the remains of rotted plants and long-dead animals trapped in sediment and later covered by ice sheets.

Permafrost soils contain roughly twice as much carbon - mainly in the form of methane and CO2 - as Earth's atmosphere. 

Speeding up global warming

When permafrost thaws, this matter warms up and decomposes, eventually releasing the carbon that it holds as carbon dioxide (CO2) and methane, gases which have a greenhouse warming effect on the planet.

The release of greenhouse gases threatens a vicious circle in the warming of the Earth.

According to a report by the Intergovernmental Panel on Climate Change (IPCC) in September 2019 a large part of the permafrost could melt by 2100 if carbon pollution continues unabated, releasing a carbon bomb of greenhouse gases. 

Frozen diseases?

The thawing of the permafrost also threatens to unlock disease-causing bacteria and viruses long trapped in the ice.​

There have already been some cases of this happening.

In 2016 a child died in Russia's far northern Siberia in an outbreak of anthrax that scientists said seemed to have come from the corpses of infected reindeers buried 70 years before but uncovered by melting permafrost.

Released from the ice, the anthrax seems to have been passed to grazing herds.

Les scientifiques ont également averti que d'autres agents pathogènes dormants ensevelis dans un sol gelé pourraient être provoqués par le réchauffement climatique, comme ceux d'anciennes tombes de variole.

En 2014, les scientifiques ont ravivé un virus géant mais inoffensif, surnommé Pithovirus sibericum , qui était enfermé dans le pergélisol sibérien depuis plus de 30 000 ans.

Un dégel du pergélisol pourrait être une aubaine pour les industries pétrolière et minière, donnant accès à des réserves auparavant difficiles à atteindre dans l'Arctique. Mais en perturbant trop profondément le sous-sol, ils pourraient réveiller les virus, avertissent les scientifiques.

La fonte du pergélisol présente également une menace sérieuse et coûteuse pour les infrastructures, risquant des glissements de terrain et des dommages aux bâtiments, aux routes et aux oléoducs.

© Agence France-Presse

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Summary | 9 Annotations
Melting permafrost
2020/06/11 14:52
is a time bomb threatening health and the environment, and risks speeding up global warming.​
2020/06/11 14:52
Locked into the permafrost is an estimated 1.7 trillion tonnes of carbon in the form of frozen organic matter
2020/06/11 14:53
releasing the carbon that it holds as carbon dioxide (CO2) and methane, gases which have a greenhouse warming effect on the planet
2020/06/11 14:53
The thawing of the permafrost also threatens to unlock disease-causing bacteria and viruses long trapped in the ice.​
2020/06/11 14:54
In 2016 a child died in Russia's far northern Siberia in an outbreak of anthrax
2020/06/11 14:54
buried 70 years before but uncovered by melting permafrost.
2020/06/11 14:54
The melting permafrost also presents a serious and costly threat to infrastructure, risking mudslides and damage to buildings, roads and oil pipelines.
2020/06/11 14:54
Pithovirus sibericum,
2020/06/11 14:54