ENGAGE
Let's return to the image of a white, broad-brimmed hat, our polar cap, if you will. We know that white, reflective surfaces don't absorb as much light energy as dark surfaces; That reflected light energy gets bounced away in another direction.
So, it seems ice does double duty when it comes to cooling our planet; Besides absorbing heat as it melts, ice also reflects light back into space before it can be absorbed and turned into heat,as do clouds and snow and any bright surface. Collectively, this reflectivity is called the Earth's albedo.
Pesky Positive Feedback
Conversely, this scenario also presents another one of those pesky positive feedback loops in nature. As more of the Arctic ice cap melts and recedes, there is less bright white ice to ward off the incoming summer solar radiation. However, the increasingly larger surface area of exposed water readily absorbs the light energy that the ice used to reflect.
As the Arctic Ocean turns more and more light into heat, it warms and melts more ice, which in turn reinforces the heating/melting cycle. And to make matters worse, remember that water has a very high specific heat capacity and can store a lot of heat for a long time, further reinforcing climate change forces.
Much of the discussion about the affects of climate change centers around the problems associated with sea-level rise and the inundation of low-lying population centers. We are told that as ice in our cold polar regions melts, sea-level increases as the ocean takes up the extra water. True enough--in part.
But there's a good reason why this module on sea ice is addressed separately from the next module on terrestrial ice--or ice on land. As it turns out, the affects of melting ice depends very much on where the ice is located. Read on...
EXPLORE
Here's another demonstration in our exciting lab series, Watching Ice Melt!
Slightly overfill a glass container with ice cubes and then add water, just so that it doesn't spill over. Let's call this container the Arctic Ocean. Then watch as the ice melts. What will happen to the sea-level in your glass as the ice melts? What will your students predict?
EXPLAIN
- What effect does melting sea ice have on sea level?
(Find the quick answer here)
EXPLORE SOME MORE...
Try This Trick!
This labs is from our exciting series, Watching the Kettle Boil.
- Safety First! Electricity, Heat, Glass, Water Hazards
- Shine a heat lamp or similar light source on two glass containers of room temperature water--one protected by or covered in white paper, and the other wrapped in black paper.
- Record the temperature of the water in each container every minute for 20-30 minutes.
- Graph the data for both containers on the same graph and compare.
EXPLAIN
- What is happening to the light energy in this activity?
- What are the roles of absorption and reflection in regulating earth's climate??
EXTEND
- Conduct these activities using Inquiry methods.
- Consider including any graphs or data in your next blog.
EVALUATE
- What are the values of these simple labs in teaching climate concepts?
EXPLORE SOME MORE...
Teachers Domain
Check out these two excellent TD interactive animations demonstrating the effects of climate change on Arctic sea-ice.
Earth's Albedo and Global WarmingArctic Sea Ice ObservationsNASA
NASA's website hosts some of the best and most current, user-friendly Earth Science resources available. This NASA link summarizes the extent of the 2009 Arctic Sea-Ice, along with other excellent media and related links.
2009 Arctic Sea-IceEXPLAIN
- How does ice-albedo positive feedback occur?
- What is the effect of melting sea-ice on sea-level?
- How do scientists track the extent of annual Arctic sea-ice?
EXTEND
- What are some ecological or cultural implications of decreasing sea-ice?
EVALUATE
- What are some of the values of interactive information websites compared to videos?
