Abstract & Conceptual Questions Saline Lakes and Global Climate Change by Sandra Zicus Jump Point: About the Case Study Case Study Abstract Conceptual Questions How to Order the Casebook About the Case Study This case study abstract is from: GeoSystems Today: an Interactive Casebook. Each printed case (in the book) starts with a list of Questions to be Explored followed by Key Learning Outcomes. An Overview and Background section then introduces the essential geosciences concepts and issues followed by a section entitled The Human Dimension. The latter section presents an integrated perspective on the "nature-society" linkages and policy implications of the case. At the end are Some Recommended Readings for more in-depth study. After you study the basic written text, and possibly do some background reading in a related textbook such as The Blue Planet: An Introduction to Earth System Science, you should take an online Virtual Tour and do the Self-Study Exercise found at the end of each case. At this point you should be ready to discuss the Conceptual Questions at the end of each case (they are repeated here as well). A suggestion–though the conceptual questions could be discussed with only the textual material as background, exploration of the online material as well would deepen your understanding and capacity to contribute meaningfully to a discussion. You are also strongly encouraged to explore some of the advanced material listed under More Activities and Learning Resources. How much more to explore is only limited by your time, interest, ingenuity and motivation! Back to Top Case Abstract Location Saline lakes are found in dry climate zones of every continent, and cover almost as much of the earth’s surface as do freshwater lakes. The volume of water contained in the Earth’s saline lakes is about 104,000 cubic kilometers, compared to a volume of 125,000 cubic kilometers for freshwater lakes (Vallentyne 1972). Many salt lakes in extremely arid regions are ephemeral, containing water only during part of the year or only during years of exceptionally high precipitation. A good example of this is Lake Eyre in Australia. During the rare occasions when Lake Eyre is at its maximum depth of about six meters, it is the seventh largest salt lake in the world. Much of the time, however, evaporation exceeds precipitation so much that the lake bed is completely dry. The majority of permanent saline lakes are found in semi-arid and subhumid climate zones where evaporation is lower. Primary Objectives The overall goal of this case study is to develop an appreciation of an important, often-overlooked ecosystem - the saline lake. This goal can be divided into three primary objectives: 1. to illustrate how these sensitive ecosystems can serve as windows to the Earth’s geologic and climatic past, 2. to increase awareness of the natural and economic importance of saline lake ecosystems, and 3. to demonstrate how human intervention with a saline lake ecosystem -the Aral Sea - has led to an ecological disaster. Background To be considered a true saline lake, a lake must contain a concentration of dissolved minerals greater than 3% by weight. For comparison, the oceans average about 3.5%. Saline lakes around the globe tend to share certain similarities: 1. They occur in arid, semi-arid, or subhumid environments where average evaporation equals or exceeds precipitation, and are usually located in the interior of a continent or in the rain shadow of a mountain range. 2. They are mostly terminal (having no outlet), and have a high dissolved salt content (more than 3% by weight). The salt concentration may be the result of evaporation of a much larger body of fresh water or of the closing off of an arm of an ocean due to tectonic forces or sea level change. 3. All have highly specialized ecosystems that are sensitive to changes in water level and salinity. 4. All are sensitive to regional changes, whether natural or human-induced, in climate or water balance. These changes lead to water level fluctuations with corresponding effects on the ecosystems, and on human populations and their settlements. Back to Top Conceptual Questions The key questions for you to examine are the following: Since most saline lakes occur in closed basins (having no outlet), how do prolonged periods of exceptionally wet or exceptionally dry weather affect the lakes? What about significant long-term changes in mean temperatures? What are the principal factors that affect saline lake ecosystems when lake levels change significantly? Why? What similarities are found in the geographic settings of the Caspian Sea, the Great Salt Lake, and Laguna Mar Chiquita? How does the basin geography affect human settlement patterns near the lakes? What factors need to be considered when developing a management plan for lake use and for land use near the lake shores? What can we learn about the Earth’s past climate history by studying saline lakes? How can this information help us predict the impacts of future global or regional climate change? Back to Top How to Order the Casebook You can order the printed casebook and see other related resources from John Wiley & Sons, Inc at the following URL: www.wiley.com/college/ Back to Top GO TO THE VIRTUAL TOURS AND EXERCISES Created 7 March 1999 .