The new abnormal: Ice cover and the ecology of the Great Lakes

Why is less Great Lakes ice a bad thing?

This year’s historically low Great Lakes ice coverage has attracted considerable attention. Less has been said, however, about what reduced ice means for the ecology of the Great Lakes. According to the National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Laboratory, effects can be profoundly negative:

  • Aquatic species, including fish, rely on ice for protecting eggs and young. Plankton, an important part of the food chain, are more resilient when protected by ice. Whitefish and lake trout will be forced to compete with warm-water species migrating north with rising temperatures. Declining ice cover could also stress whitefish reproduction in Lake Superior where ice protects eggs from winter storm disturbance.
  • Reduced ice cover leads to increased evaporation, which in turn could lead to drastic reductions in Great Lakes water levels.
  • Nearshore ice sheets buffer coastal structures and infrastructure from winter’s punishing winds and waves. Less ice leaves them more vulnerable to costly damage.
  • Low ice cover fosters increased resuspension of sediments and may contribute to summer algae blooms.
  • Reduced ice cover leads to extreme weather, including increasing intensity and frequency of heavy rainfall and snowfall, including record lake effect snows.
  • Recreational sports, including ice fishing on the Great Lakes and inland lakes, are reduced or eliminated, cutting into culturally important harvests of whitefish, panfish, bass and yellow perch.

“The Great Lakes will continue to warm over the next several decades and despite year-to-year variability, Lake Erie is trending towards an ice-free status during the winter months,” says Dr. Mike McCay, director of the University of Windsor’s Great Lakes Institute for Environmental Research. “Even though we have seen the lakes bounce back from adversity before, less ice cover will be a new normal.”

Great Lakes Ice Cover, 1973-2023 (click to play slideshow)

Great Lakes annual maximum ice cover, 1973-2023

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