Potential Effects on Water Levels by Glacial Melting

Lesson Description: Students develop a hypothesis and design an experiment that shows potential effects of water levels by glacial melting

 

Background:      "If the global temperature rises, polar ice caps will melt more. This water will flow into the sea resulting in a rise in sea level." This is the common message heard particularly through media hype, but is it true? The fact is that global warming sea level rises will not be caused by massive Arctic or Antarctica ice melts. The actual prediction by scientists is that the rise in sea level will be caused by the expansion of ocean waters due to a rise in ocean water temperatures.       To understand why there will be a minimal effect on sea level by massive glacial melts we need to look at the difference between the Arctic and Antarctica regions. The Arctic region is mostly water with floating polar ice (the only exception is Greenland which does have glaciers). The melting of this ice cover would have no effect on the sea level because the ice is already displacing the water it is in.  Antarctica, however, contains glaciers or land ice . If this region were to begin to melt, there would be a great increase in sea level because the water stored in these glaciers would then flow into the seas.      So why then are massive melt predictions not in the forecast? Studies have considered two sets of reasoning. First, the global warming trends will be felt more in the northern hemisphere than the southern hemisphere. This will probably be due to changes in albedo (reflection) in the north. Second, according to Dick Wetherald of the Geophysical Fluid Dynamics Lab in Princeton, New Jersey, scientific models have indicated that the reason the Antarctic Ocean fails to warm significantly is due to the fact that there is a downward mixing of sea water in and around the Antarctic continent.  Any warming of these waters must encompass a very deep layer.  As a result  any warming of the ocean surface must be spread throughout this entire deep layer and, therefore, there is very little heat left over to cause the ocean surface to respond to global warming.  Eventually, about a thousand years or more, the ocean surface will respond.      This scenario should not, however, minimize the catastrophic effect of rising sea levels due to thermal expansion and the melting of mountain glaciers. This threat is real and has been forecasted by many reputable scientists. Predictions are that worldwide sea level increases have been approximately 2 - 5 cm within the last century. If this trend continues, predictions are for the possibility of 12  additional inches by 2060. Many coastal areas in the U.S. would be inundated with water and literally disappear. These coastal cities include New York, Miami, Charleston, Boston and New Orleans. Entire island nations as well as nations in low lying delta areas would also be at great risk. In 1995, short term predictions of about a 2 inch increase by the year 2000 have been made. This small change nonetheless greatly impacts aquatic and coastal ecosystems and will increase the damage brought by heavy storms such as hurricanes and nor'easters.

 

Teacher Notes: You can use this activity as a prelude to a discussion concerning the potential effects of glacial melts.  When preparing materials for students, all containers of frozen water should have a set amount of liquid. Students should be given this information so that they may develop a controlled experiment. It may be easier to use a set number of ice cubes so that students will be able to replicate that number. Students can use heat lamps to control the melting process.

 

Unit Length:   one lab period

Grade Level:  grades 7 - 12. Adaptable for younger students.

Materials:   This materials list is just a suggestion. You can have students brainstorm for creative ways to design this lab.
                        cups
                        graduated cylinders
                        ice cubes
                        small plastic bottles containing frozen water
                        heat lamp

The Student Lab:

• Formulate two hypotheses:

1. concerning the change in water level when ice is floating in liquid water
2. concerning the change in water level when ice melt is added to liquid water.
 
• Design an experiment that could test your hypotheses.
• Be sure to get teacher permission before attempting lab.

Assessment:
Use the following links to help you develop innovative alternative forms of assessment.

          Concept mapping links:
           1) Lesson in teaching concept maps to students-visual included
           2) More in depth example of a concept map - detailed visual included
           3) Teacher instructions and tips

            Rubrics:
            1) Teacher Links On Rubrics
            2) Rubric Information - Advanced Secondary
 
Extension:      Research the geography of the Arctic Circle and  the Antarctica.
                        Research the effects of the short term rise in sea level for your area.
 
 
 

Bibliography and Additional Sources:
    
                        (These links will take you off our site.
                        You might want to bookmark this site before you leave.)

Mercury Rising: Global Warming Conference, Kyoto, Japan
Diagrams showing the effects of global warming on U.S. cities
http://www.foxnews.com/news/packages/globalwarming/newyork_photo.sml
 
Could Waterworld Really Happen?
Summary concerning the differences between the Arctic Ocean and Antarctica ice melts.
http://ds.dial.pipex.com/ritson/earth/water

The EPA Global Warming Site: Impacts- Coastal
Summary concerning the probability and impact of rising sea levels.
http://www.epa.gov/globalwarming/impacts/coastal/index.html

Woodrow Wilson Leadership Program in Environmental Science lpt@www.woodrow.org
The Woodrow Wilson National Fellowship Foundation webmaster@woodrow.org
CN 5281, Princeton NJ 08543-5281 Tel:(609)452-7007 Fax:(609)452-0066