Explain how positive feedback mechanisms in the Arctic contribute to accelerating global warming.

IB DP Biology Higher 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 covers approximately 25% of the Northern Hemisphere's land surface and contains large quantities of organic carbon accumulated over thousands of years. As global temperatures rise, this permafrost begins to thaw.

Model answer (4 marks)

1. Melting Arctic sea ice and snow lowers the surface albedo, so less solar radiation is reflected back to space.
2. The exposed ocean and land absorb more solar energy, raising local temperatures.
3. Thawing permafrost releases stored organic carbon as CO₂ and CH₄ via microbial decomposition.
4. These greenhouse gases strengthen the greenhouse effect, causing further warming that accelerates both ice melt and permafrost thaw, completing the positive feedback loop.

Examiner tips

Use the exact terms: albedo, greenhouse effect, CO₂, CH₄, positive feedback.\nShow the causal chain in order.\nMention both ice‑melt and permafrost as separate but linked mechanisms.\nKeep each point brief – one sentence per mark.

Common mistakes

Confusing albedo with emissivity; writing “reflectivity” alone.\nFailing to link the released gases back to the greenhouse effect.\nUsing vague wording like “more warming” without specifying the mechanism.

Mark scheme (4 marks)

Melting of Arctic sea ice / snow reduces albedo (reflectivity) of the Earth's surface
Increased absorption of solar energy by exposed ocean / land causes further warming, reinforcing the initial temperature rise
Thawing permafrost releases stored carbon as carbon dioxide and/or methane through decomposition by microorganisms
Released greenhouse gases enhance the greenhouse effect, causing further warming which in turn drives more permafrost thaw / ice melt, completing the positive feedback loop

Key terms in this question

positive feedback