Arctic Tundra Shifting from Carbon Sink to Carbon Source

Why in News

Recent analysis from the Arctic Report Card by the National Oceanic and Atmospheric Administration (NOAA) confirms that the Arctic Tundra has transitioned from a carbon sink to a carbon emitter.

About the Arctic Tundra

• Definition: The Arctic Tundra is a vast biome defined by its cold, dry, and treeless landscape. The word “tundra” is derived from the Finnish term tunturi, meaning a “treeless plain.”
• Characteristics:
  • Permafrost: Permanently frozen soil starts within a meter of the surface. Only the top layer thaws during summer, limiting plant root growth and tree formation.
  • Soil: The nutrient-poor, rocky soil has slow decomposition rates, leading to the buildup of organic materials such as peat (decayed sphagnum moss) and humus (organic matter), which act as carbon sinks.
  • Geography: Spanning 11.5 million km², the Arctic Tundra is the northernmost biome, covering areas north of the Arctic Circle, parts of Canada, Iceland, and Greenland.
  • Climate:
    • Temperatures range from 15.5°C in summer to -60°C in winter, with subzero conditions lasting 6–10 months.
    • Annual precipitation is 150–250 mm, with minimal evaporation.
    • Experiences continuous daylight in summer and total darkness in winter.
  • Vegetation: Predominantly herbaceous plants like grasses, mosses (e.g., reindeer moss), lichens, and liverworts dominate due to the short growing season. Dwarf willows and similar woody plants adapt to the harsh winds by remaining small and spreading out.
  • Wildlife:
    • Large mammals such as polar bears, caribou, musk ox, and Arctic foxes thrive in the tundra.
    • Smaller animals like lemmings and Arctic hares exhibit seasonal fur color changes for adaptation.
    • Migratory birds, including loons and snow geese, breed here during the summer months.

The Arctic Tundra as a Carbon Sink

Despite the lack of trees, the Arctic Tundra has been a vital carbon sink for millennia. Cold temperatures slow decomposition, trapping carbon in:

• Peat: Decayed sphagnum moss.
• Humus: Decomposed organic material.

Transition to a Carbon Source

• Thawing Permafrost:
  • Rising temperatures activate microbes, breaking down organic matter and releasing carbon dioxide (CO₂) and methane (CH₄).
  • Methane is particularly potent as a greenhouse gas.
• Increased Wildfires:
  • Amplify greenhouse gas emissions.
  • Accelerate permafrost thawing.
• Rising Temperatures:
  • The Arctic is warming four times faster than the global average.
  • 2024 is recorded as the second-warmest year since 1900.

Global Carbon Emission Trends

• CO₂ emissions are projected to reach 41.6 billion tonnes in 2024, compared to 40.6 billion tonnes in 2023.
• Land-use changes contribute an additional 4.2 billion tonnes of carbon emissions annually.