Century-long data reveals complex trends in ice cover in the Laurentian Great Lakes

Ice cover on large lakes regulates regional weather and aquatic ecosystems, and understanding lake ice responses to climate change is critical for environmental management. However, lake-wide ice records are generally restricted to the remote sensing era, limiting inferences about long-term shifts in climate. Here, we use continuous air temperature records to reconstruct lake-wide ice cover for each of the Laurentian Great Lakes between 1898 and 2022, assessing the skill of a statistical model against satellite observations from recent decades. Reconstructed ice records reveal a prominent multidecadal oscillation (~60-year period) superimposed on a century-scale warming trend that is significantly weaker than trends inferred over recent decades (1975 − 2022). We find that trends and variability are strongly associated with the Atlantic Multidecadal Oscillation, indicating a persistent ocean-atmosphere-lake interaction that modulates North American winter conditions. Results show that short observational windows can overstate ice trends and underrepresent internal variability. These findings highlight the need for century-scale records to disentangle decadal climate variability from the persistent effects of anthropogenic warming when assessing regional cryosphere change. Trends and interannual fluctuations in ice cover in the Laurentian Great Lakes are well correlated with the Atlantic Multidecadal Oscillation and show a weaker long-term decline than post-1975 trends, according to a study reconstructing 1898–2022 ice cover from air temperature data validated with satellites.