Explain how changes in sea ice coverage in polar regions can create a positive feedback loop that accelerates 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).

Model answer (4 marks)

Sea ice has a high albedo, reflecting most incoming solar radiation back into space.

When global temperatures rise, sea ice melts, reducing the extent of ice cover.

The exposed ocean surface has a lower albedo, absorbing more solar radiation and warming the water.

This additional warming melts more ice, reinforcing the initial loss and creating a positive feedback loop that accelerates climate change.

Examiner tips

Use the term ‘high albedo’ for ice and ‘low albedo’ for ocean. Show the sequence: melt → lower albedo → more absorption → further melt. Keep each point short and directly linked to the feedback.
Include the word ‘positive feedback loop’ to demonstrate understanding of the concept.

Common mistakes

Confusing ice with snow albedo or omitting the lower albedo of ocean.
Failing to mention that the loop is ‘positive’ and that it accelerates warming.

Mark scheme (4 marks)

Sea ice has a high albedo / reflects a large proportion of incoming solar radiation back into space
As global temperatures rise, sea ice melts / decreases in extent, exposing darker ocean water beneath
The exposed ocean surface has a lower albedo / absorbs more solar radiation, causing further warming
This additional warming causes further ice melt, reinforcing the original change and forming a positive feedback loop

Key terms in this question

sea ice · positive feedback · climate change