What is permafrost?

• Permafrost is ground that remains completely frozen at 0 degrees Celsius or below for at least two years. It is defined solely based on temperature and duration.
• The permanently frozen ground, consisting of soil, sand, and rock held together by ice, is believed to have formed during glacial periods dating several millennia.

Geographical distribution:

• These grounds are known to be below 22 per cent of the land surface on Earth, mostly in polar zones and regions with high mountains.
• They are spread across 55 per cent of the landmass in Russia and Canada, 85 per cent in the US state of Alaska, and possibly the entirety of Antarctica.
• At lower latitudes, permafrost is found at high altitude locations such as the Alps and the Tibetian plateau.

Active layer:

• While permafrost itself is always frozen, the surface layer that covers it (called the “active layer”) need not be frozen.
• In Canada and Russia, for example, colourful tundra vegetation carpet over permafrost for thousands of kilometres.
• Its thickness reduces progressively towards the south, and is affected by a number of other factors, including the Earth’s interior heat, snow and vegetation cover, presence of water bodies, and topography.

Climate change and Permafrost:

• The Earth’s polar and high altitude regions, its principal permafrost reservoirs  are the most threatened by climate change.
• According to the USA’s National Oceanic and Atmospheric Administration, Arctic regions are warming twice as fast compared to the rest of the planet, its current rate of temperature change being the highest in 2,000 years.
• A study has shown that every 1 degree Celsius rise in temperature can degrade up to 39 lakh square kilometre due to thawing. 
• This degradation is expected to further aggravate as the climate gets warmer, putting at risk 40 per cent of the world’s permafrost towards the end of the century– causing disastrous effects.

Impacts of thawing permafrost:

• Threat to infrastructure
  • As temperatures rise, the binding ice in permafrost melts, making the ground unstable and leading to massive potholes, landslides, and floods.
  • The sinking effect causes damage to key infrastructure such as roads, railway lines, buildings, power lines and pipelines that serve more than 3.5 crore people that live in permafrost regions.
• Massive trove of pathogens
  • Beneath its surface, permafrost contains large quantities of organic leftover from thousands of years prior, dead remains of plants, animals, and microorganisms that got frozen before they could rot. These grounds could release ancient bacteria and viruses into the atmosphere as they unfreeze.
• Greenhouse gas emissions
  • When permafrost thaws, microbes start decomposing this carbon matter, releasing greenhouse gases like methane and carbon dioxide. 
  • Researchers have estimated that for every 1 degree Celsius rise in average temperature, permafrost grounds could release greenhouse gases to the tune of 4-6 years’ of emissions from coal, oil, and natural gas , becoming a major factor of climate change in themselves.
• Threat to natural ecosystems
  • Thermokarst lakes are the depressions formed when thawing permafrost collapsed and filled with meltwater are important for wildlife and provide water to local communities.
  • But if the underlying permafrost continues to thaw, lakes and wetlands can drain completely, destroying these biologically important resources.

Why in the news?

The principal reason that led to the recent 20,000-tonne oil leak at an Arctic region power plant in Russia that is now being recognised is the sinking of ground surface due to permafrost thaw.

Reference:

https://www.sciencealert.com/as-permafrost-melts-ancient-viruses-and-now-fuel-spills-are-being-unleashed

https://indianexpress.com/article/explained/russia-arctic-oil-leak-permafrost-6450195/