Explain how a positive feedback mechanism involving Arctic permafrost can amplify the effects of climate change.

IB DP Biology Standard Level (2023 syllabus) — D4.3 Climate change · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Permafrost is frozen ground found across much of the Arctic. As global average temperatures rise, permafrost thaws and the organic matter within it begins to decompose.

Model answer (4 marks)

Thawing permafrost allows microorganisms to decompose previously frozen organic matter, releasing CO₂ and CH₄ into the atmosphere.
These gases increase the atmospheric greenhouse‑gas concentration, enhancing the greenhouse effect.
The enhanced greenhouse effect causes further warming of the Arctic.
This additional warming thaws more permafrost, completing a positive feedback loop that amplifies climate change.

Examiner tips

Use the exact terms: permafrost, decomposition, CO₂, CH₄, greenhouse effect, positive feedback loop.
Show the causal chain in order: thaw → decomposition → gas release → warming → further thaw.
Keep each point brief but complete; 4 marks allow one sentence per point.

Common mistakes

Confusing permafrost with general soil; not specifying the gases released.
Using vague terms like "more heat" instead of "enhanced greenhouse effect”.
Omitting the word "positive" when describing the feedback loop.

Mark scheme (4 marks)

Thawing permafrost allows decomposition of previously frozen organic matter by microorganisms/decomposers
Decomposition releases greenhouse gases (carbon dioxide and/or methane) into the atmosphere
Increased atmospheric greenhouse gas concentration enhances the greenhouse effect, causing further warming
This is a positive feedback loop because the initial warming causes further thawing, which releases more greenhouse gases, driving yet more warming

Key terms in this question

permafrost · positive feedback