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Global Change and Sustainability FOLE_C18FF.QXD 9/10/08 6:39 PM Page 268 EXERCISE 18 Global Change and Sustainability INTRODUCTION doubters are funded by special interest groups and fossil fuel coalitions that do not want research on, or “The public in the industrialized nations, particularly in evidence of, global change that could impact their the United States, must be made more aware of the economic condition (Gelbspan, 1997). Island nations, pervasive trends in environmental degradation and environmentalists, active geoscientists, environmen- resource depletion, and of the need to modify pat- tal economists, and insurance organizations were terns of life to cope with these trends.” among the first to recognize that global change is —KAULA AND ANDERSON, PLANET EARTH COMMITTEE, occurring. Now many groups are working on adapta- AMERICAN GEOPHYSICAL UNION, 1991 tions to change and on ways to reduce human “The time to consider the policy dimensions of cli- impact globally. mate change is not when the link between green- We should be able to adapt to the limits of our house gases and climate change is conclusively habitat on Earth without overshooting them. Many proven Á but when the possibility cannot be dis- organisms undergo increases and collapses in their counted and is taken seriously by the society of populations but they do not have our technology, which we are part. We in BP have reached that information, and understanding. We have models, point.” examples, and explanations of why societies collapse (Diamond, 2005). We probably will never understand —JOHN BROWNE, GROUP CHIEF EXECUTIVE, how the total Earth system works; however, we need BP AMERICA, 1997 to write the “Operating Manual for Spaceship Earth.” The quotations above capture the concern of many The final activity in this exercise is constructing a geologists who understand Earth history and scenario—your description of the future viewed from change in the Earth system. In the distant past 50 years in the future. This forecasting approach is humans did not play a role in these changes. Now used by think tanks to understand possible futures we do. In this exercise we look at changes in cli- (Schwartz, 1991). mate using ice cores and glacier retreat, changes in the atmosphere through ozone and CO2 , and the human component of change through population increase and the response to projected temperature change. PART A. ICE-CORE PALEOTEMPERATURES Other components of global environmental AND GLACIER RETREAT change include deforestation and habitat loss, loss of biodiversity (which may be the most important one), Ice cores provide excellent records of past atmospheric desertification, soil erosion and agriculture, spread of conditions, including temperatures and CO2 concentra- infectious disease by microorganisms, rising sea tions. Interpreting cores from ice caps in mid-latitude and level, modifications in weather patterns and stormi- equatorial regions has been the research focus of Lonnie ness, and decreasing water resources. and Ellen Thompson’s Ice Core Paleoclimatology A very few scientists do not accept the evidence Research Group at the Byrd Polar Research Center, The of warming, or if they do, its relation to human activity. Ohio State University. Material in this part of the exer- These few doubters receive “equal time in the press” cise has been provided by the Thompson team. Images with those actively working on the science of global of the Quelccaya Ice Cap are available at http://bprc change. It has been revealed that many of the .osu.edu/Icecore/ 268 FOLE_C18FF.QXD 9/10/08 6:39 PM Page 269 Exercise 18 • Global Change and Sustainability 269 Basic concepts in this section include: oxygen iso- b. How could the record of the Huaynaputina volcanic topes in ice provide information on atmospheric tempera- eruption be used to date this ice core (Figure 18.1b)? ture fluctuations—lower delta 18O values (written d18O) indicate lower temperatures; cold glaciers, well below the melting point, are required for extraction of annual records—any melting mixes the annual signal; with increasing altitude atmospheric temperatures decrease— if ice cap melting now occurs where it did not in the past, 2. During this period, would you expect mountain glaciers in the atmosphere has warmed; and, retreat of valley or the region to have advanced (due to less summer melting) or outlet glaciers is due to warmer temperatures or less retreated (due to more summer melting)? Explain. accumulation of snow and ice to replenish the glacier. Worldwide, almost all mountain glaciers are retreating due to increased atmospheric temperatures. In the recent past, a few glaciers were advancing because the warmer 3. From the record in 18.1a, has the last century at Quelccaya air temperatures have produced more snow. been warmer or cooler than the three centuries before 1900? QUESTIONS 18, PART A 1. Study Figure 18.1a, the oxygen isotope record for the 4. Between 1963 and 1991, significant retreat and lowering of Quelccaya Ice Cap in Peru. This ice cap is fed by moisture an outlet glacier of the Quelccaya Ice Cap was observed. from the Amazon Basin. Although glaciers may not respond immediately to climate a. Were temperatures warmer or colder than the mean for change, if increased temperature was the cause of this the record during the period from A.D. 1550 to 1900? retreat, is this explanation consistent with temperature data in Figure 18.1a? Why or why not? 5. In 1600 the Rhone Glacier in Switzerland was in an advanced position. A four-story building, erected about 1950, now covers the glacier’s former terminal position. Does this evidence agree or disagree with the ice core record in Figure 18.1a? 6. In parts of Glacier Bay, near Juneau, Alaska, glacier ice was near its maximum in 1820. Since that time, the ice has retreated more than 45 miles in this fiord. Does this Little Ice Age (about 1450 to 1850) advance of ice in Glacier Bay, and the retreat that followed, agree with the ice-core record from Peru (18.1)? Explain. 7. Study Figure 18.2 A, B, C, D, and E. This figure presents the oxygen isotope profiles for the tropical Quelccaya Ice FIGURE 18.1 Oxygen isotope (a) and particle record (b) from Cap drilled in 1991 on the summit dome (A) and cores the 1983 Quelccaya, Peru, ice core. More negative d18O values drilled in 1976 on the summit dome (B), the middle dome (per mil) indicate cooler temperatures during precipitation. (C), and the south dome (D). The north-to-south cross sec- Mean values in a and b given by vertical lines. Wind blown or tion of the Quelccaya Ice Cap (E) illustrates the locations volcanic dust-particle concentrations are given as number of from which the oxygen isotope records in A through D were particles per milliliter of sample. The Huaynaputina, Peru, volcanic drilled and the position of the percolation line in 1976 and eruption is indicated by *. 1991. The percolation line is the altitude on the glacier below (Modified from L. Thompson et al., 1986; L. Thompson, pers. which melting of snow and subsequent percolation of water comm. 1991, 2008; used with permission) through the snow and firn occurs. FOLE_C18FF.QXD 9/10/08 6:39 PM Page 270 270 IV. Introduction to Sustainability: Resource Planning and Global Change FIGURE 18.2 Oxygen isotope profiles (A to D) and north–south cross section (E) for the Quelccaya Ice Cap, Peru. Records A and B are from Summit Dome; C is from Middle Dome and D is from South Dome. Dashed lines are the altitudes (meters above sea level, masl) for the percolation or melting line. (Modified from L. Thompson, pers. comm., 1991, 2008; used with permission) a. How do the mean isotopic values at the summit core c. Why are the distinctive annual spikes seen in the 1976 drilled in 1991 compare with those drilled in 1976? (See summit core missing or subdued in the 1991 summit mean values at bottom of each record) core? (Hint: Compare 1991 summit record with the record from South Dome.) b. What does the change in mean isotopic value between 1976 and 1991 at Summit Dome suggest about atmos- pheric temperatures in this part of the World? 8. In 1991 the percolation line was above the Summit Dome (Figure 18.2E). How many meters has the percolation line risen between 1976 and 1991? FOLE_C18FF.QXD 9/10/08 6:39 PM Page 271 Exercise 18 • Global Change and Sustainability 271 9. Melting now occurs at Summit Dome that did not occur b. Has the rate increased from that during the 1963–1991 there in 1976, indicating that the air temperature has period? warmed. We know that the temperature of the atmosphere changes by 0.7° C for each rise in elevation of 100 meters (0.007° C/1 meter). This is the atmospheric lapse rate. Using your answer in Question 8 and this lapse rate, calculate the 13. To help understand the impact of even small changes in temperature change that took place at Summit Dome temperature, we now look at “the year without a summer.” between 1976 and 1991. Volcanic events are recorded in ice cores as seen in Figure 18.1b where the eruption of Mt. _____ is shown by an ash layer. On April 5, 1815, Mount Tambora in Indonesia began erupting and injected ash and gases (e.g., H2O, CO2 , HCl, SO2 , N2) into the stratosphere. Some of these gases (for instance, HCl) have the potential to affect the ozone O layer; most act to 1 32 10. Study the photos (Figure 18.3) of the Qori Kalis Glacier, enhance the greenhouse effect, but sulfate (SO4) droplets in the the largest outlet glacier from the Quelccaya Ice Cap.
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