In late October, the National Oceanic and Atmospheric Administration (NOAA) reported that Lake Superior’s water temperatures were almost three degrees Celsius higher than the usual average. On October 20, the historical average temperature for Lake Superior stands at 8.8 degrees Celsius. However, this year, on the same date, the surface temperature of the water measured at 11.6 degrees Celsius, marking the second-highest temperature recorded for that day. The warmest temperature ever recorded on October 20 was in 2021.
Northwestern Ontario experienced abnormally warm fall weather, resembling August more than October, breaking several daytime temperature records by up to nine degrees Celsius. This unseasonable warmth has contributed to Lake Superior maintaining a relatively warm temperature for this time of year. This trend, observed over recent years, has implications for underwater ecosystems and coastal weather patterns.
Researchers like Jay Austin, a physical oceanography PhD and professor at the University of Minnesota Duluth, have been studying these seasonal temperature fluctuations. Austin emphasized the significant impact of warm air temperatures on Lake Superior. He mentioned that warm air temperatures result in a slower cooling rate for the lake, showcasing a predictable relationship between air and water temperatures.
Data on water temperatures in the Great Lakes, collected through instruments and satellite readings for decades, indicate a gradual increase in Lake Superior’s temperatures over the last 40 years. Austin highlighted that higher-than-average water temperatures can influence ecosystems, potentially fostering the growth of algae blooms.
According to Great Lakes Integrated Sciences and Assessment (GLISA), Lake Superior is among the fastest-warming lakes globally. GLISA attributes this trend partly to earlier spring ice melt, leading to extended periods of lake stratification and increased exposure to solar radiation. GLISA’s findings reveal that summer surface temperatures on Lake Superior rose 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 more winter research on the Great Lakes to anticipate future scenarios. Xenopoulos emphasized the need to monitor nutrient runoff into the Great Lakes due to expected warmer weather. She stressed the importance of providing accurate information to the millions of people residing around the Great Lakes to ensure the safety of their drinking water.
Increasing awareness of the ongoing changes will empower individuals to adapt to climate variations around lakes such as Superior and implement strategies to mitigate potential adverse effects.