Climate change and the Great Lakes

The Great Lakes contain 20 percent of the world’s freshwater (McBean 2008) and are already facing the impacts of anthropogenic climate change. The Greats Lakes have seen a 10 to 25 percent increase in precipitation from 1981 to 2010 (NOAA, 2019) due to increased evaporation. The amount of precipitation is predicted to increase by 12.5 percent by 2080 (Wang 2016). Increased rainfall has led to increased nutrients washed out of soils, as found in two studied watersheds (Wang 2018). In one watershed the amount of phosphorus washed out, due to soil erosion, could increase by 108 percent by 2099 (Ibid). These additional nutrients can result in nutrient loading and therefore algae booms and eutrophication in the Great Lakes.

One reason for the increased precipitation is the reduction in ice cover, which results in more evaporation. Ice cover has decreased by 71 percent on the Great Lakes from 1973 to 2010 (Collingsworth, 2017). Many commercially important fish species allow their eggs to overwinter below the ice, with reduced ice cover their eggs are more susceptible to wave action damage (Ibid). Models to predict how much ice coverage will be reduced vary widely but they all agree that the coverage will reduce by 2050. One initial benefit of reduced ice cover is that it will reduce the number of winter kills as there will be more circulation of oxygen.

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