Don t like the weather? Wait ten minutes. has been a phrase used by many in the Great

Transcription

1 Climate Change in the Great Lakes Michael John Michalek Don t like the weather? Wait ten minutes. has been a phrase used by many in the Great Lakes region. With weather and temperature extremes being pushed to their limits in recent years, it is hard for people to not be generally concerned. Global warming and climate change have allegedly been the cause for extensive changes in water levels, precipitation amounts, ice coverage, temperature fluctuations, and natural weather patterns in the Great Lakes. The rapid increase of CO 2 in the atmosphere from human caused emissions and rising ocean temperatures are mainly responsible for these current changes. Increased industrialization is providing fuel to the problem and more dramatic changes are inevitable in the future of the Great Lakes. For the past 139 years, research has been conducted on water level trends throughout the entire Great Lakes region. The study recognizes normality in lake level rises and drops throughout the course of a year during the time period. For example, spring snow melt accounts for an increase in water levels while the dryer summer and early fall season records the lower levels. The study shows that the Great Lakes water levels have had roughly a one month advance in the seasonal cycle (Lenters 2001). Therefore, suggesting spring snowmelts are occurring earlier in the spring and the dry summer season is lasting longer. The rise in CO 2 is suspected to be the reason for this advance in the cycle. Rising CO 2 is responsible for allowing celestial heat to enter the atmosphere and not escape, consequently warming the planet. As an outcome of the rising CO 2, Great Lakes water levels are projected to lower 0.5 to 2.5 meters because of a reduction in precipitation amounts, lowering the overall basin water supply (Lenters 2001). Wetland disappearance is also occurring because drainage practices and drier conditions, causing

2 low lake level trends to be more significant on account of the vanishing added influx given by the marshland. Rising temperatures have more implications than just raising the mercury on your thermometer, especially for those in the Great Lakes. Areas downwind of large fetches (distance of open water) on the Great Lakes generally acquire generous amounts of lake effect snow during the winter season. Much of Michigan, up-state New York, and eastern Ontario usually accumulate large amounts of lake effect snow with the common westerly winds. In order for the process to occur a number of things need to happen. The water body needs to be warmer than the overlying passing air mass. The larger the difference there is between temperatures, the more snow generally accumulates downwind. Other factors such as fetch and elevation play into the process as well. For the past 80 years, monitoring stations in the region have been recording snow amounts. Sites within the lake effect producing areas were deemed lake-effect sites, and sites outside the area were called non lake-effect sites. The lake-effect sites reveal an overall statistically significant increasing trend since 1931, while the non lake-effect sites show no major changes (Burnett 2003) (Figures 1 and 2). This increase in the lake-effect area Figure 1. Lake Effect Sites (Burnett 2003) Figure 2. Non-Lake Effect Sites (Burnett 2003) is thought to be related to increasing temperatures, coincidently warming the water body, thus increasing the temperature differences between water and air. Decreasing ice cover is also

3 happening in the Great Lakes. Ice records taken from sites on each of the five Great Lakes since 1824 has indicated that ice thaw dates are coming earlier and freeze-up dates later in the year (Assel 1995) (Figure 3). If the general trend continues ice cover may be reduced by one to two months, allowing shipping and dredging to increase in cost and lengthen. Figure 3. Ice Records (Assel 1995) Figure 4. Changing Climate (Union of Concerned Scientist 2005) Ice declines will also reduce dissolved oxygen levels in shallow lake basins and increase fish productivity (Smith 1991). By the year 2095 (Figure 4), the Great Lakes climate will be very similar to present day Arkansas. Estimated temperatures for the turn of the century are projected to be 1.5 0C to 4.5 0C higher than today because of the amount of CO 2 is expected to double (Union of Concerned Scientist 2005). Along with a changing climate comes a change in typical weather events and patterns. Many scientists have gathered together to compile various weather scenarios with computer simulators that take atmosphere, land, ocean, and sea data into consideration. A study on winter mid-latitude cyclone activity in North America in 2007, claiming that cyclone frequency will increase from the Great Lakes region to Quebec and decreases over the US east coast, suggesting

4 a possible northward shift of the Atlantic storm tracks under a warmer climate (Teng 2007). This will likely produce more extreme weather events around the Great Lakes due to elongated cyclone paths. While more precipitation is likely, the warmer climate will increase the probability of drought, therefore not compensating. Precipitation in the region is also expected to have different seasonal distribution, increasing in winter and decreasing in summer (Union of Concerned Scientist 2005). This will cause harsher winters and dryer summers, weather that is not enjoyed by many. The growing season will become longer but with less precipitation different types of crops and plants may have to be grown naturally. Global warming and climate change will occur in the future. A reduction in our overwhelming large consumption in fossil fuels may slow the process but will inevitably not bail us out of this situation. Enough damage has been done to the atmosphere to cause climatic changes that will continue to progress into the future. In the Great Lakes area, which is native to upwards of 60 million people these transformations will, overtime, disrupt many ways of life. Whether it is decreasing water levels, changing precipitation amounts, reduced ice coverage, temperature fluctuations, or changing natural weather patterns, change will be notable. These subtle shifts may not be as overwhelming in our lifetime, but will definitely be prominent to future generations.

5 Bibliography Assel, R. A., D. M. Robertson, M. Hoff, J. Selgery. Climatic change implications of long-term ( ) ice records for the Laurentian Great Lakes. Ann. Glaciol 21 (1995): Burnett A. W., Kirby M.E., Mullins H.T., Patterson W.P. Increasing Great Lake-Effect Snowfall During the Twentieth Century: A Regional Response to Global Warming? doi: Lenters, J. D. Long-term trends in the seasonal cycle of Great Lakes water levels. Journal of Great Lakes Research 27, no. 3 (2001): Smith, Joel B. The Potential Impacts of Climate Change on the Great Lakes. Bulletin of the American Meteorological Society 72, no. 1 (1, 1991): Teng H., Washington W. M., Meehl G.A. Interannual Variations and Future Change of Wintertime Extratropical Cyclone Activity Over North America in CCSM doi: Union of Concerned Scientists. "Confronting Climate Change in the Great Lakes Region: Impacts on Our Communities and Ecosystems." Union of Concerned Scientists Web site (accessed January 31, 2011).

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