Permafrost

Topic: World Climate Classification: Koeppen's Scheme · NCERT: Class 11, Ch 11 "World Climate and Climate Change"

Meaning

Permafrost is ground (soil, rock or sediment) that stays at or below 0°C for at least two years in a row. It matters because it holds old plant matter that has stayed frozen for a long time. When it thaws, it releases greenhouse gases that cause more warming [4]. Thawing ground also sinks, so buildings, roads and pipelines built on it get damaged.

Explanation

How permafrost forms and where it sits

• The cause is a long, very cold climate.
• In the tundra climate (ET), the warmest month averages only between 0°C and 10°C.
• Summer is too short and too cool to warm the ground deeply.

• So the deeper ground never thaws, and it stays frozen year after year.

• The test is temperature, not ice. Ground counts as permafrost if it stays at or below 0°C for two straight years. This is true whether it is soil, rock or sediment.

• Frozen ground is hard and acts like rock. Thawed ground turns soft and sinks.

Its two parts: active layer and permafrost

• Active layer: the thin top layer above the permafrost. It thaws each summer and freezes again in autumn.
• In the coldest areas it is only about 10–15 cm thick [3].

• In warmer permafrost areas it can be several metres thick [3].

• Permafrost: the ground below the active layer. It stays frozen through every summer.

• Why it matters for plants:
• Water from the thawed top layer cannot drain down through the frozen ground.
• The surface becomes waterlogged (soaked and boggy).
• Tree roots cannot grow in it. Only shallow-rooted mosses, lichens (small crusty plants made of a fungus and an alga living together) and low flowering plants survive. This treeless cover is the tundra.

Permafrost thaw as a climate feedback

• Feedback means a result that makes its own cause stronger.
• The chain:
• The world warms, so permafrost thaws.
• Microbes start to break down old plant matter that was frozen in the soil.
• They release carbon dioxide and methane, both greenhouse gases [4].

• More greenhouse gas means more warming, and more warming means more thaw.

• Methane release also happens in winter. More than 50% of yearly methane release from Arctic soils happens in the cold season, not only in summer [2].

Damage when it thaws

• The chain:
• Frozen ground holds structures up like rock.
• When it thaws, it turns soft and sinks.

• Buildings tilt, roads crack and pipelines break.

• Example: the Norilsk fuel spill (2020) in Siberia, Russia. A fuel tank failed and spilled diesel into rivers. The thawing ground sinking under the tank was blamed.

Where it occurs

• Extent: permafrost zones cover nearly a quarter of the exposed land of the Northern Hemisphere [2].
• World: under the tundra (ET) belt along the Arctic Ocean. This belt lies mostly poleward of about 70° latitude.
• Northern Canada
• Alaska (USA)
• Northern Siberia (Russia), including Norilsk, the site of the 2020 fuel spill

• Coastal strip of Greenland (Denmark)

• Not in the ice cap (EF) zones: the interiors of Greenland and Antarctica are covered by thick ice sheets, not by tundra with an active layer.

• India: the high cold areas of Ladakh and the high Himalaya face similar risks to roads and buildings from frozen ground. These are highland climates, where temperature falls with height. The normal lapse rate (the fall of temperature with height) is about 6.5°C for every 1,000 m.

Don't confuse with

• Active layer: the top layer that thaws every summer. Permafrost is the ground below it that does not thaw for at least two years in a row.
• Ice sheet (ice cap climate, EF): a thick mass of ice on the surface, built up from snow that never melts. It is found in interior Greenland and Antarctica. Permafrost is frozen ground under the tundra (ET), and it has a thin thawed layer on top in summer.
• Tundra: the name of the climate (ET) and its vegetation (mosses, lichens, low flowering plants). Permafrost is the frozen ground condition beneath that vegetation.
• Seasonally frozen ground: ground that freezes in winter and thaws in summer is not permafrost. The test is staying frozen for at least two consecutive years.

Prelims Hooks

• Permafrost = ground at or below 0°C for at least two consecutive years. It can be soil, rock or sediment, not only ice.
• The active layer thaws in summer. It is about 10–15 cm thick in the coldest areas and several metres thick in warmer ones [3].
• Permafrost zones cover nearly a quarter of the Northern Hemisphere's exposed land [2].
• Climate type match: permafrost with an active layer belongs to the tundra (ET), where the warmest month is 0–10°C. Thick ice sheets belong to the ice cap (EF), where all months are below 0°C.
• Trap: Arctic soils do not release methane only in summer. More than 50% of their yearly methane release happens in the cold season [2].
• Gases released on thaw: carbon dioxide and methane, produced when microbes break down old frozen plant matter [4].

Mains Points

• Permafrost thaw as a climate tipping risk (GS-I/GS-III):
• Warming thaws permafrost. Microbes then release CO₂ and methane, which cause more warming [4].

• Large releases even in the cold season [2] make Arctic methane a hidden threat to global climate goals.

• Infrastructure and disaster risk (GS-III):

• Thawing ground sinks, so buildings, roads and pipelines in Russia, Canada and Alaska fail. The Norilsk fuel spill (2020) in Siberia was blamed on ground sinking under a fuel tank.

• Roads and buildings in India's high Himalaya and Ladakh face similar risks. Building there needs designs that keep the ground frozen and checks of ground temperature.

• Link to climate and vegetation (GS-I):

• Permafrost explains why the tundra has no trees. Frozen subsoil blocks drainage and roots, so the surface stays waterlogged.
• It shows how Koeppen's temperature rules (warmest month 0–10°C) connect directly to soil, vegetation and how people use the land.

Related concepts

• Polar climates (E)
• Tundra climate (ET)
• Ice cap climate (EF)
• Iceberg

Read more

• Group E: polar climates, and highland (H) climates