Insights into Great Lakes ice coverage decreases (Credit: GLISA)

Discussion: The Great Lakes are one of Earth’s most precious freshwater resources, holding about 20% of the worlds freshwater and numerous different economic resources; whether that be fishing, tourism, and state and national parks alongside the shoreline. Within recent decades, thirty-seven years to be exact, the Great Lakes have experienced an overall ice coverage decrease of about 71%. More specifically, Lake Ontario has had a decrease of 88%, Lake Superior 79%, Lake Michigan 77%, Lake Huron 62%, Lake Erie 50% and finally, although a minor but substantial body of water, Lake St. Clair 37%. Ice coverage on the Great Lakes is highly variable from year to year. This variability can be attributed to natural climate patterns that result from the Arctic Oscillation and El Nino Southern Oscillation which both effect surface air temperatures in the Great Lakes region. Although such climate forcing are only short-term, overall Great Lake ice coverage decrease can be related to a warming climate.

     Major economic and societal impacts have yet to occur, but few are being seen currently. If you live in the Great Lakes region then you are very familiar with lake-effect snow. With less ice coverage, this will produce more evaporation which, in turn, will cause more precipitation. Ice on the Great Lakes acts as an “evaporation seal”—diminishing the amount of moisture being brought up to the atmosphere. Matter of fact, the difference between water and air temperatures play a key role in evaporation. Warmer waters lead to less ice coverage, and mixing that with cooler air temperatures will lead to larger rates of evaporation. For example, in January of 2014 Lake Superior’s water temperature was 30-40 degrees Fahrenheit warmer than the air above. That drastic difference between water and air temperature led to high evaporation rates.

     While lake-effect snow can have dangerous societal impacts, what about ecological impacts that a decrease in lake ice could have? Many northern ecosystems heavily rely on ice coverage throughout the winter. Plankton, for instance, become more resilient when protected by ice and would lose population mass with less ice. Also, cold-water fish species such as whitefish and lake trout would have no choice but to compete with warm-water fish species as they move north to warmer temperatures. Lastly, with warmer temperatures in lakes, oxygen levels would actually decrease in the lower levels of the lakes due to the overall lake becoming warmer. Colder water temperatures can hold more oxygen than warmer temperatures. The increase in water temperature and lack of oxygen would produce so called “dead zones.” With dead zones, toxic algae blooms would take place like those seen in Lake Erie around spring and early Summer time. In this case, all of the Great Lakes would experience these algae blooms which would be detrimental to fish species and the overall ecology of the Great Lakes.

     Ice coverage in the Great Lakes is variable from year to year with some years having above average and below average coverage. Overall, the trend for ice coverage over the past couple decades has undoubtedly decreased, which will pose future societal and economic impacts.
            
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©2018 Weather Forecaster Alec Kownacki