Arctic Tundra: From Carbon Sink to Source

Context:

The Arctic tundra, a region that has stored vast amounts of carbon for thousands of years, is now emitting greenhouse gases (GHGs) such as carbon dioxide (CO₂) and methane (CH₄). This finding is part of the National Oceanic and Atmospheric Administration (NOAA)’s recent analysis, the Arctic Report Card.

Background

The Arctic Report Card, published annually by NOAA, provides a comprehensive overview of environmental changes in the polar region, highlighting critical shifts in its ecosystems.

How Does the Arctic Tundra Store Carbon?

In typical ecosystems:

• Plants absorb CO₂ through photosynthesis.
• Carbon moves through the ecosystem as plants and animals grow, die, and decompose, with microorganisms releasing CO₂ back into the atmosphere, completing the carbon cycle.

In the Arctic tundra, however:

• The decomposition of organic matter is dramatically slowed down due to the cold climate.
• Permafrost (frozen soil) traps plant and animal remains, preventing CO₂ from being released.
• Arctic soils store over 1.6 trillion metric tonnes of carbon, roughly double the carbon present in the atmosphere.

Why Is the Arctic Tundra Emitting More Carbon Than Absorbing It?

In recent years, the Arctic tundra has transitioned from a carbon sink to a carbon source due to:

1. Rising Temperatures:

   • The Arctic is warming four times faster than the global average.
   • Thawing permafrost activates microbes that break down organic matter, releasing CO₂ and CH₄ into the atmosphere.

2. Increased Wildfires:

   • The Arctic has experienced frequent and intense wildfires in recent years.
   • Wildfire smoke adds to GHG emissions and accelerates permafrost thaw.
   • 2020 marked the worst wildfire season in the Arctic's recorded history.

Together, these factors caused the Arctic tundra to release more carbon than its plants absorbed between 2001 and 2020, potentially for the first time in thousands of years, according to NOAA’s report.

This alarming shift underscores the need for urgent global action to mitigate climate change and its cascading impacts on sensitive ecosystems like the Arctic tundra.