Scientists have recorded a significant decrease in Arctic sea ice over the past 50 years. Explain how human activities have led to this decrease in Arctic sea ice.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Arctic sea ice extent has declined by approximately 13% per decade since satellite records began. Scientists link this decline to rising global temperatures caused by human activities.
Model answer (5 marks)
Human activities such as burning fossil fuels and deforestation release large amounts of carbon dioxide and other greenhouse gases into the atmosphere.
These gases trap infrared radiation emitted by the Earth’s surface, increasing the amount of heat retained in the atmosphere.
The resulting rise in global temperature causes the Arctic region to warm, so that the rate of sea‑ice melt exceeds the rate of new ice formation.
As sea ice melts, the surface albedo decreases, meaning less sunlight is reflected back into space. This further increases local temperatures, accelerating ice loss in a positive feedback loop.
These gases trap infrared radiation emitted by the Earth’s surface, increasing the amount of heat retained in the atmosphere.
The resulting rise in global temperature causes the Arctic region to warm, so that the rate of sea‑ice melt exceeds the rate of new ice formation.
As sea ice melts, the surface albedo decreases, meaning less sunlight is reflected back into space. This further increases local temperatures, accelerating ice loss in a positive feedback loop.
Examiner tips
- Use the exact terms: ‘greenhouse gases’, ‘infrared radiation’, ‘global warming’, ‘albedo’, ‘positive feedback’.
- Show the causal chain step by step – each point earns a mark.
- Mention the rate of melt exceeding formation to link temperature rise to ice loss.
Common mistakes
- Confusing the source of greenhouse gases (e.g. saying only natural sources).
- Failing to mention the albedo feedback or the rate of melt exceeding formation.
Mark scheme (5 marks)
- Human activities (such as burning fossil fuels / deforestation) release carbon dioxide (and other greenhouse gases) into the atmosphere
- Increased levels of greenhouse gases in the atmosphere trap / absorb more heat (infrared radiation) from the Earth's surface
- This leads to an increase in global temperature / global warming
- Higher temperatures cause Arctic sea ice to melt / the rate of melting exceeds the rate of ice formation
- Melting of sea ice reduces the reflectivity (albedo) of the Arctic surface, causing further warming and further ice loss (positive feedback)
Related
- All Pearson Edexcel A-Level Biology A (9BI0) revision notes →
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- Decode the mark scheme abbreviations →
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