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Return Back Differential Effects of Melting Ice Sheets
Teacher Background


Waleed Abdalati"People all over the world should care about what happens at the Poles because the Poles influence climate worldwide. They help keep the planet cool, they're a critical element of the global ocean circulation system and so changes at the Poles can greatly influence ocean circulation, temperatures worldwide and this has implications in Florida, or in San Diego. The other element that particularly coastal regions need to be thinking about is changes in sea level. As the great ice sheets, Greenland and Antarctica shrink, oceans will rise and we're seeing clear evidence that they are shrinking in size. How much and what it will look like in the future is still debatable. But they are shrinking and that raises sea level."

From an interview with Waleed Abdalati, head of the Cryospheric (ice) Science Division NASA Goddard Space Flight Center.

Researchers differentiate between ice in ways most people students and the public do not. That's because ice found in different places over land or floating on the ocean behaves in very different ways with different consequences. Researchers speak of "ice sheets" when talking of ice on land, and "sea-ice" (of course) for ice floating on the oceans. Glaciers, moving "rivers" of frozen water, flowing down from mountains through the force of gravity, are found on land, and an "ice shelf" refers to ice still attached to land stretching out over the oceans. Chunks of ice which break off are "ice bergs." These two Activities invite students to simulate and observe the different effects on "sea level" from melting "sea-ice" and land-based ice sheets.



Activity 1:
When Floating Ice Melts

Objective

To have students investigate whether melting sea-ice affects sea level.

Engage

As global temperature increases heat up the upper layers of the ocean, they will cause some of the large amounts of floating ice in the Antarctic and Arctic Oceans to melt. Will the melting sea ice add more water to the oceans and cause sea levels to rise? Ask students to write down or verbally respond. (The answer is no.)

Explore/Explain

Materials: (for each team of 4 students)
  • container
  • pitcher of water
  • several trays of ice cubes
Procedure:
  1. Place the ice cubes in the container
  2. Fill the container with the water until full.
  3. Watch the water level as the ice melts.
Follow up:
  1. Would melting ice cause sea level to rise?
  2. What are the reasons for the answer?
  3. Have students discuss the differences, if any, between what they predicted and what they observed.
Extend

The Beaufort Sea in the Arctic Circle has experienced remarkable change in sea ice cover over the last 5 years. The recent summer minimum of sea ice extent has receded approximately 200 km north compared to the 1979-2000 mean summer minimum ice extent. Climate models suggest that Arctic sea ice could decline dramatically this century. Are the changes being observed in the Beaufort Sea a precursor of these predicted conditions, or will the system revert back to 1970's state? How might such a reduction in sea ice cover affect the Arctic system as a whole? In April 2007, 30 scientists from, Italy, Iceland, Germany, UK and the US will take part in APLIS 07, one of the first major science campaigns of the 4th International Polar Year. For two weeks they'll camp out on the Beaufort Sea, while studying sea ice, microbial activity, and mercury cycling in the Arctic. There will be plenty of world-class science, as well as extreme adventure. POLAR-PALOOZA will be on site capturing material for vlogs, podcasts, blogs and more. Stay tuned. To learn more about APLIS 07 and other field expeditions, link to the HDvCC section of the Polar-Palooza website.



Activity 2:
When Land Ice Melts

Objective

To demonstrate what happens when ice sheets on land melt and how they affect sea level rise differently than melting sea-ice.

Engage

The Arctic and Antarctic are covered with large sheets of ice. Other islands like New Zealand or Greenland have ice masses called glaciers covering the land. When land-based ice melts, more water flows into the sea, and sea level rises. However, the land previously covered by the ice, rises as well when the heavy load is removed. Icebergs in the ocean are broken off bits of land ice.

Materials: (for each team of 4 students)
  • A large rectangular container
  • Piece of wood (approximately 5 cm x 15 cm)
  • Several trays of ice cubes
  • Pitcher of water
Procedure:
  1. On the surface of the wood, mark north, south, east and west
  2. Going from north to south, draw line going east to west at 2 millimeter intervals
  3. Fill the container with water and place the wood in the water
  4. Put a couple of ice cubes on the N edge of the floating wood
  5. Watch and note the level of water in the container and on the N and S edges
Follow-up:
  1. What happens to the north and south edges of the block of wood as the ice melts?
  2. Will melting glaciers and other land-based ice masses cause sea level to rise?
  3. Will it submerge the continents on which the ice used to be?
  4. Most of the world's tide gauges are on the edge of continents that in the recent geologic past had massive ice sheets on them. Can we get a good measure of trends in the world's sea levels from gauges if we do not properly consider the vertical land movements?

Extend

Research scientist and "exploration engineer" Dr. Alberto Behar of NASA's Jet Propulsion Laboratory has been part of several long-term field campaigns investigating Greenland's fast moving glaciers. In May 2007, he will return to Greenland and our HDvCC crew will accompany him as part of a 5-week taping trip that will take them to various field sites, including Summit Station where some of the Arctic's deepest ice cores have been drilled and Ilullisat, the base for exploration of the West Greenland Ice Sheet. This dynamic area of Earth's northern polar region is not well understood and is responding rapidly to climate change. Previous NASA measurements using global positioning system data show the ice there moves an average of about 20 centimeters (8 inches) a day, accelerating to about 35 centimeters (14 inches) a day during the summer melt. Their study the first of its kind in this region will provide a better understanding of the factors affecting one of the largest and most vulnerable ice sheets on Earth.

Note: Thanks to the Office of Science, Department of Energy for permission to adapt these two activities.


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POLAR-PALOOZA and the materials on this website are based upon work supported by the National Science Foundation under Grant No. 0632262. Any opinions, findings and conclusions or recommendations expressed in this material are those of PASSPORT TO KNOWLEDGE/Geoff Haines-Stiles Productions, Inc., and do not necessarily reflect those of the National Science Foundation.
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