US Long-Term Ecological Research Network

Most research investigating effects of global warming on lake temperature focus on relatively large lakes and neglect to ask whether small lakes show similar responses. Because the majority of lakes in the world are small, the large-lake focus thus may not capture temperature trends representative of the majority of the world’s lakes. To analyze the temperature trends in lakes across Wisconsin, we used the cross-site seasonal Sen’s slope estimator, a non-parametric technique for trend estimation that reduces assumptions made when correcting for seasonality. Our analysis reveals important size-dependent differences in thermal responses to climate change even when subjected to similar regional climate drivers. Large lake warming was consistent throughout the water column while small lakes (area< 0.5 km2) warmed only in the shallow waters. The different behavior of these small lakes has relevance to the full distribution of U.S. lakes as they represent 99% of lakes by number and 30% of lake surface area. These differences in warming patterns are important for predicting the impacts of climate change on both biogeochemical cycles and the distribution and available habitat for lake biota.

NTL Keyword