In the latter part of October, the National Oceanic and Atmospheric Administration (NOAA) reported that Lake Superior’s water temperatures were nearly three degrees Celsius higher than the long-term average. On October 20, the typical temperature for Lake Superior is 8.8°C, but this year it measured 11.6°C, marking the second-highest reading on record for that date. The warmest temperature ever recorded on October 20 was in 2021.
Unusual mild autumn weather this year transformed October into a month resembling August in northwestern Ontario, shattering multiple daytime temperature records by up to nine degrees Celsius in the area. While the immediate effects of the warm fall weather may not be readily apparent, it appears to be contributing to maintaining Lake Superior’s warmth for this season, continuing a trend seen in recent years that affects underwater ecosystems and coastal weather conditions.
Researchers like Jay Austin, a physical oceanography Ph.D. and professor at the University of Minnesota Duluth, have been monitoring seasonal temperature variations for years. Austin highlighted the significant impact of warm air temperatures on Lake Superior, noting that warmer air temperatures result in a slower cooling rate for the lake. He emphasized the strong correlation between air and water temperatures, indicating that understanding air temperatures can reliably predict water temperature changes.
Observations of water temperatures across the Great Lakes through instrument and satellite data collection have been ongoing for decades. Austin pointed out that over the past four decades, Lake Superior’s water temperatures have been gradually rising. Elevated water temperatures can influence ecosystems, potentially fostering the growth of algae blooms in the lake.
According to Great Lakes Integrated Sciences and Assessment (GLISA), Lake Superior is among the fastest-warming lakes globally. The research group attributes this trend partly to earlier spring ice melt, leading to extended periods of lake stratification and increased exposure to solar radiation. GLISA’s data reveals that summer surface temperatures on Lake Superior have increased by an average of 2.5°C between 1979 and 2006.
Margueritte Xenopoulos, a professor at Trent University and Canada Research Chair in Global Change of Freshwater Ecosystems, along with her research colleagues, advocates for increased winter scientific studies on the Great Lakes to anticipate future scenarios. Xenopoulos emphasized the importance of forecasting potential nutrient runoff into the Great Lakes due to warmer weather and its implications for drinking water safety for the millions of people residing near the lakes. Enhancing understanding of ongoing changes will aid in adapting to climate variations around Lake Superior and devising strategies to mitigate adverse impacts.
