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NOVA scienceNOW: Fastest Glacier

Viewing Ideas

Before Watching

1. On a map, have students locate Greenland and Antarctica on the map. Tell them that Greenland's continental ice sheet contains the second largest amount of frozen freshwater in the world, after Antarctica. Next, have them locate the Jakobshavn Isbrae glacier on the western coast of Greenland. Have them distinguish between a continental ice sheet and a glacier. (A continental ice sheet is a thick layer of ice [often measuring in miles] that covers a vast geographical area on the scale of a continent, such as Antarctica or Greenland. A glacier is a body of ice showing evidence of movement, such as the presence of ice flowline, crevasses, and moraines. Glaciers are much smaller than continental ice sheets, which have many glaciers along its edges.) Ask students what might explain why so many places in Greenland have Scandinavian names. (Greenland is a Danish territory, and many early explorers, including the Vikings, were from Scandinavia.)

2. To make sure students understand how glaciers form, have teams brainstorm three ways one might form. While the teams are brainstorming, write statements a-f (below) on the board. (The sequence is intentionally incorrect.) Later, the students' task will be to put the statements into the proper order.

   1. The residual snow settles, becoming more compact and dense.

   2. The great weight of the top layers compacts the deep layers.

   3. Snow falls.

   4. Annual snow accumulation far exceeds the annual snowmelt.

   5. Compacted snow freezes together and creates sheets of ice.

   6. The number of layers increases.

   After five minutes, have teams share one of their ideas. Write it on the board. Continue until all ideas have been shared. Ask students to put statements a-f in the proper order. (To save time, have students refer to the statements by letter. The correct sequence is: C, D, A, F, B, E.) Every idea on their list of brainstormed glacier-formation ideas is bound to include some—or even all—of these steps. Have the class review these ideas and identify which of the a-f steps were identified and which were missed. Tell them that once a glacier forms, gravity causes it to slide slowly downhill, making glaciers veritable rivers of ice. Glaciers vary in size from about the size of a football field to hundreds of miles long and advance at different rates—anywhere from a few inches to over 100 feet per day.

3. On the Web, have students find the average winter and summer temperatures for their area and for Greenland. A good site to try is http://www.wrh.noaa.gov/psr/general/monsoon/. How do they compare? How have Greenland's temperatures changed over the last decade?

4. Have students predict what might happen to the Greenland continental ice sheet if average temperatures continue to rise the way they have over the past decade—a summer temperature increase of 1.5-2 degrees Celsius and a winter temperature increase of 6 degrees Celsius. Ask students how they think the continental ice sheet might respond to these changes.

After Watching

1. The study of weather and climate offers many different career paths. Some of the careers in this segment include glaciologist, climatologist, satellite technologist, pilot, and videographer. Have each student choose a career of interest and write a paragraph describing what he or she finds appealing about it and what some of the challenges might be. Then ask students who have chosen the same career to work together and make a poster that displays typical aspects of the job as well as the coursework and degrees necessary for entering the profession. Have student groups present their posters.

2. Ask students to differentiate between climate and weather. (Climate relates to the average weather conditions over a long period of time. Weather refers to atmospheric conditions at a particular time and place.) Write weather and climate statements in a three-column chart on the board and challenge the class to determine which each relates to—climate or weather. Then have students come up with their own weather-related and climate-related statements.

   Statement	Weather	Climate
   Greenland is cold most of the year.		X
   It's snowing.	X
   It's warm today.	X
   We live in a temperate zone.		X
   We live on the prairie.		X
   This is the rainy season.	X

   
   

   Ask students whether glaciers are a better gauge of climate or weather. (Climate) Have them surmise whether scientists who study glaciers are more likely to be climatologists or meteorologists. (Climatologists, because glaciers take hundreds to thousands of years to form. Thus, climate has a greater impact on glaciers.)

3. Universities often combine their weather and climate curricula with other fields of study. Make a two-column chart and ask students to suggest how weather or climate is related to each field.

   Subject	Relationship to Weather/Climate
   Earth science	Volcanic eruptions, ice sheets, and atmospheric change can alter weather and climate.
   Oceanography	Cold and warm currents influence temperature.
   Geography	Surface features affect the impact weather has on the land.
   Engineering	Cities are engineered for specific climatic conditions.
   Political science	Politicians vote on environmental bills related to weather and climate.
   City Planning	City planners consider a region's climate when designing city areas.

4. In their attempt to comprehend what is happening to the Jakobshavn Isbrae glacier, climatologists gather temperature, humidity, and wind speed data. Help students understand their local weather patterns by having them set up a weather station at school that includes a rain gauge, a thermometer, and if possible, an anemometer (wind gauge). Ask students to record their daily weather data in a chart and graph their findings each week. At the end of each season, discuss students' data and graphs. Compare this information to last year's weather pattern for your area. (iwin.nws.noaa.gov/iwin/graphicsversion/bigmain.html) Brainstorm how warming or cooling might affect your local area. Contact your local television meteorologist to see if your school can have its weather observations reported on the daily weather program.

5. The Jakobshavn Isbrae glacier's speed increased from one foot a day to an astounding 113 feet per day. One reason is that summer meltwater seeps through the ice to the bottom of the glacier, slightly lifting it. The water also acts as a lubricant, and the glacier's speed increases because it slides more easily. Have students test the lubricating ability of water by comparing how various materials move across a desk. Test a wood block, a large eraser, and an ice cube. Discuss how easily each object moved. Point out that ice slides easily because as it melts, water forms a layer between the desk and the ice and acts as a lubricant. Test whether the wood or eraser move more easily over a wet or a dry surface.

6. Scientists stated that the glacier dumps 12 trillion gallons of freshwater into the ocean each year. This is equivalent to the amount of water in all the streams and rivers in the U.S., and it is 12 times the amount that is discharged daily into the oceans by U.S. streams and rivers. To relate the concept of 12 trillion gallons to a familiar situation, have students call the local Water Department and find out how much water your city or town uses each year. How many years would it take for your city or town to use 12 trillion gallons?

Web Sites

All About Glaciers
nsidc.org/glaciers/
Describes the life of a glacier and includes information about where and how glaciers develop.

Greenland's Receding Ice
svs.gsfc.nasa.gov/stories/greenland/
Provides images, animations, and descriptions of how Greenland's ice cap is thinning.

Major Greenland Glacier, Once Stable, Now Shrinking Dramatically
researchnews.osu.edu/archive/greenice.htm
Discusses the satellite data pertaining to the shrinking of the Jakobshavn Isbrae glacier.

Books

Glacier Ice by Austin Post and Edward R. Chapelle. University of Washington Press, 2000.
Describes how glaciers form and change and has several aerial photographs of glaciers from around the world.

Global Warming by Fred Pearce. Dorling Kindersley, 2002.
Explores evidence related to global warming and considers the impact warming could have on Earth.