Climate Change in Polar Regions (College Board AP® Environmental Science) : Study Guide

Polar regions & the albedo effect

What is the albedo effect?

• Albedo refers to the reflectivity of a surface; ice and snow have a high albedo, meaning they reflect most of the sun’s energy back into space

  • Polar regions covered with ice and snow reflect up to 90% of solar radiation, helping to regulate Earth’s temperature

How climate change affects the albedo effect

• Polar regions are showing faster response times to global climate change (i.e. they are experiencing faster effects of climate change) due to a phenomenon called "ice-albedo feedback."

• As global temperatures rise, ice and snow in polar regions melt

  • This reduces the albedo of polar regions

  • Darker ocean and land surfaces exposed by melting ice absorb more solar energy, increasing local temperatures

• This process creates a positive feedback loop:

  • More warming leads to more melting, which in turn leads to even more absorption of heat

Real-world examples

• The Arctic sea ice extent has decreased by about 13% per decade since 1979

• In Greenland the ice sheet is melting rapidly, contributing to sea-level rise

Positive feedback & climate response time

What is positive feedback in polar regions?

• Positive feedback refers to processes that amplify changes in a system rather than stabilizing it

  • In polar regions, positive feedback mechanisms accelerate warming and ice loss

Key positive feedback loops

Melting sea ice feedback

• As sea ice melts, it exposes darker ocean water with a lower albedo, causing more solar energy to be absorbed

  • This leads to increased local warming, which melts more ice, continuing the cycle

Thawing permafrost feedback

• Permafrost is permanently frozen ground that stores large amounts of carbon and methane

  • When permafrost thaws, it releases methane, a potent greenhouse gas that further warms the atmosphere

  • Example: The Siberian Arctic has shown increased methane emissions as permafrost thaws

Climate response time in polar regions

• Climate response time refers to how quickly a system reacts to changes in climate forcings

• Polar regions show a faster response time (relative to some other planetary regions or systems) due to amplified feedbacks like sea ice melt and permafrost thawing

Consequence of the loss of ice and snow in polar regions

Impact on species dependent on ice

• Species like polar bears, seals, and walruses rely on sea ice for hunting, breeding, and resting

  • As ice disappears, these species are forced to travel longer distances and expend more energy to find food

  • Example: Polar bears are observed swimming greater distances between ice floes, which increases energy expenditure and decreases survival rates

Impact on marine food webs

• Ice algae growing under sea ice are a primary food source for small marine organisms like krill

  • With less ice, ice algae production declines, reducing food availability for krill, fish, and larger predators

  • Example: The Antarctic krill population has been affected by shrinking ice cover, impacting species like penguins and seals

Coastal impacts

• Melting glaciers and ice sheets contribute to sea-level rise, which erodes coastlines and floods low-lying areas

  • Communities in Alaska and other Arctic regions face increased coastal erosion and threats to coastal infrastructure