In late October, the National Oceanic and Atmospheric Administration (NOAA) reported that Lake Superior’s water temperatures were nearly three degrees Celsius higher than the historical average. On October 20, the typical temperature for Lake Superior is 8.8 degrees Celsius. However, this year on the same date, the surface temperature was recorded at 11.6 degrees Celsius, marking the second-highest temperature ever observed for that day. The warmest temperature recorded on October 20 was in 2021.
Unusual warm fall weather this year transformed October into what felt like August in northwestern Ontario, breaking several daytime temperature records by up to nine degrees Celsius. Despite the immediate effects of the warm fall weather not being immediately visible, it appears to be contributing to maintaining Lake Superior’s warmth for this season, continuing a trend observed in recent years that impacts underwater ecosystems and coastal weather.
Researchers like Jay Austin, a physical oceanography Ph.D. and a professor at the University of Minnesota Duluth, have been studying seasonal temperature variations for years. Austin emphasized the significant influence of warm air temperatures on Lake Superior, stating that when air temperatures are high, the lake cools down at a slower rate. He highlighted that understanding air temperatures can reliably predict water temperatures.
Austin mentioned that water temperature data across the Great Lakes have been collected through instruments and satellite readings for decades. Over the past 40 years, water temperatures in Lake Superior have been gradually rising. Above-average water temperatures can affect ecosystems, such as promoting the growth of algae blooms.
According to the Great Lakes Integrated Sciences and Assessment (GLISA), Lake Superior is among the fastest-warming lakes globally. The group attributed this trend partly to earlier spring ice melting, leading to longer periods of lake stratification and increased exposure to solar radiation. GLISA reported that summer surface temperatures on Lake Superior have risen 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 changes. Xenopoulos highlighted that warmer weather is projected to escalate nutrient runoff into the Great Lakes, potentially impacting water safety for the millions of people living around these lakes. She stressed the importance of monitoring these changes to provide essential information for the well-being of communities relying on the Great Lakes.
Increasing knowledge about ongoing changes will aid in adapting to climate variations around lakes like Superior and implementing strategies to mitigate potential negative consequences.
