Scientists at the US National Oceanic and Atmospheric Administration (NOAA) project that the maximum Great Lakes ice cover for 2021 will be 30%, which is higher than last year’s maximum of 19.5%, but that a long-term pattern of declining ice cover, likely driven by climate change, remains. The maximum typically occurs between mid-February and early March.
The 30% projected maximum ice cover forecast is an average of ice coverage across the five Great Lakes. Using an improved forecast system, NOAA’s team at the Great Lakes Environmental Research Laboratory (GLERL) have said they will update seasonal ice cover projections twice a month. Each iteration will take into account the most recent surface air temperature data leading to a more accurate forecast.
“Great Lakes ice cover often swings back and forth between higher and lower levels with each new year,” said Jia Wang, ice climatologist at NOAA GLERL. “Global climate patterns such as El Nino play a major role in driving these changes. But if annual cycles are removed, a long-term trend is visible showing that overall ice cover has been declining by 5% per decade based on 1973-2020 data.” Wang attributes the decline to human-caused climate change, primarily rising atmospheric temperature.
The 2021 maximum ice cover prediction of 30% is significantly lower than the long-term average maximum coverage of 53%. The 2021 prediction is higher than the 2017 and 2020 maximums (both about 19.5%) and much lower than the 2018 maximum of 70% percent and the 2019 maximum of 81%.
NOAA GLERL produces ice projections using a model that ingests statistical ice data as well as data on global air circulation patterns. Its research has shown that the year-to-year variability of Great Lakes ice cover is heavily influenced by four large-scale climate patterns referred to as teleconnections: the North Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO), the El Nino/Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). These patterns affect Great Lakes regional climate and ice cover by influencing the location of the westerly jet stream over North America.
GLERL produces ice projections for the five lakes taken together as well as individual lakes. Each lake has a different pattern of ice cover with Lake Erie often experiencing the highest percentage of ice cover because its shallow water accelerates freezing.
The maximum ice cover projections for each lake are as follows:
Lake Superior: 30%
Lake Michigan: 23%
Lake Huron: 39%
Lake Erie: 63%
Lake Ontario: 7%
Experimental ice cover projections will be updated twice monthly and can be found on the NOAA GLERL Ice Cover Forecasting page.