2-12: Sea-Level Rise

Pre-Class Preparation

Objectives

To review the record of past sea level conditions and understand the causes of global sea-level rise.
To understand the dynamics that lead to changes in major fresh water reservoirs (ice masses) and how these reservoirs are vulnerable to global climate change.

Procedure

Read the learning unit.
Class images
Take the learning unit quiz. Quizzes are available from your portfolio. You may access your portfolio via the list of students participating in this years course, as represented by the icon below.

Additional Required Reading. Although you are not ultimately responsible for content listed in this section, we encourage you to fully explore the links in order to provide a better scope on the upcoming class discussion.

	West Antarctic Ice Sheet has Collapsed in a Previous Warm Period.
	Satellite data shows global sea level rise. (Note: This site is currently being updated.)
	Climate change and sea level. (From UNEP.)
	Higher temperatures in Antarctica have let to disintegration of some ice shelves, Chemical & Engineering News, November 27, 1995.
	The special concern of coastal areas and small island states. (From UNEP. )
	Houghton, J. T., L. G. Meira Filho, B. A. Callander N. Harris, A. Kattenberg, and K. Maskell, 1996: Climate Change 1995. The Science of Climate Change. Cambridge University Press, 363-397.
	Houghton, J. T., G. J. Jenkins, and J. J. Ephraums, 1990: Climate Change, The IPCC Scientific Assessment. Cambridge University Press. p. 263-278.

Class Discussion

Problem to ponder...
How is it possible that increased snowfall over Antarctica could be a confirming signal for global warming?

Class Discussion Summary: submitted by classmate Matt R. Bryner

The topic of the March 23 lecture was SEA LEVEL. To begin this discussion, Dr. Takle stated that it has been estimated that the oceans have risen by 1-2mm/yr. for the last one-hundred years (or about 4 inches total). There are many sources for error, however. These include interannual variations, meteorological and oceanic forcing, historic geographical bias, and vertical land movements. One important thing to note is that over the last 100 years, the rate at which the sea is rising has not increased. This may be true if one looks at the last 200 years -- in which case there is some evidence that the rate is increasing.

Dr. Takle listed some of the contributing factors of the rise in the sea level -- thermal expansion of the oceans, glaciers and small ice caps, Greenland’s ice sheet, and the Antarctic ice sheet. If the glaciers were all ablated into water, it would cause an increase of 35 cm to the oceans’ level. Greenland’s ice sheet would add 7 m to this. Antarctica would add 65 m. The latter 2 would have dramatic effects along the continents’ coastlines. Antarctica has by far the most ice, nearly 90%. One section, The West Antarctica Ice Sheet acts as a cantilever beam out from the continent. If it fell into the ocean the sea would rise by 7 m.

Dr. Takle finished the hour discussing a scenario that kept him from sleep. It deals with ice on mountain tops and changing altitude of the zero degree Celsius isotherm. The scenario was an irreversible process occurring in 5 steps. There were...

In each step with ice present, there is some ice below the isotherm due to gravity flow down the mountain. Dr. Takle asked for a good explanation of why there is not ice in step 4. My explanation would be that until the isotherm (everything remaining the same) drops below the top of the mountain, there is no place for the ice to accumulate. It may possible fall from the sky above to the top of the mountain, but until the right conditions present themselves (step 5) the accumulation with end up as liquid on the mountain top.

Post-Class Activities

Participate in the electronic dialog. Use this forum for:

continuing class discussion;
posing new questions to students or the instructor;
responding to issues/questions raised by students in class/electronic dialog.

Visitor Access (Visitors are welcome to participate in the dialog. Just click on the icon below)	Student Access (Students must post all dialog from their portfolio. Click on the icon below to access the student list.)

Recommended Reading Materials

	Antarctica and Greenland mass balance problem. This exercise was created by Joe Smith, a senior in Meteorology (Class of 1996). For additional information about this exercise, email: sigep@iastate.edu.
	One Small Ice Shelf Dies, One Giant Iceberg Born. British Antarctic Survey Press Release, February 1995.
	Loss of Coastal Upland to Relative Sea-Level Rise Woods Hole Oceanographic Institution
	Borecker, W. S., 1994: Massive Iceberg Discharges as Triggers for Global Climate Change. Nature 372, 421.
	Clark, P. U., D. R. Macayeal, H. T. Andrews, and P. J. Bartlein, 1995: Ice sheets play important role in climate change. EOS 76, 265-270.
	Fahnestock, Mark. 1996: An Ice-Shelf Breakup. Science 271, 775-776.
	Houghton, J.T., G.J. Jenkins, J.J. Ephraums, eds, 1990: 1990 Intergovernment Panel on Climate Change, Cambridge University Press, 263-279.

References

	Potential Impacts of Sea-Level Rise on Populations and Agriculture from the Sustainable Development Dept. (SD), Food and Agriculture Organization of the United Nations (FAO)
	Coastal Tool Catalog, NOAA's Coastal Services Center
	Rising Sea Level Threatens Wetlands
	Bindschadler, R., and P. Vornberger, 1998: Changes in the West Antarctic ice sheet since 1963 from declassified satellite photography. Science 279, 689-692.
	de Wolde, J. R., R. Bintania and J. Oerlemans. 1995: Thermal Expansion of the Ocean Over the Last Hundred Years. Journal of Climate, 8, 2881-2891.
	Goodess, C.M. & J. P. Palutikof & T. D. Davies. 1992: The Nature and Causes of Climate Change, Assessing the Long Term Future. Studies in Climatology Series.
	Oerlemans, J., 1994: Quantifying Global Warming from the Retreat of Glaciers. Science, 5 April 1994, 243-245.
	Raymo, M. E., 1998: Glacial puzzles. Science 281, 1467-1468.