Drivers of Globally Distributed Lake Surface Water Temperature Trends, 1985-2009

Abstract

Climate change may have profound implications on aquatic ecosystems by increasing lake surface water temperatures. Increasing surface water temperatures have been demonstrated to affect the distribution of fish species, primary productivity rates, and food web dynamics of aquatic systems. It is important to understand how lake surface water temperatures (SWT) are changing globally, and what drivers are influencing these changes. Changes in lake surface water temperatures of 78 globally distributed lakes were assessed between 1985 and 2009. Ninety percent of the lakes studied experienced increasing SWT trends over the 25-year period. Histograms were developed to investigate patterns in various morphological and climatic variables with regards to SWT trends. In addition, a regression tree analysis was performed in order to investigate the drivers of SWT trends. The trend in summer solar radiation was the most important predictor of summer surface water temperature trends of the globally distributed lakes, such that mean surface water temperatures increase with increasing summer solar radiation. Summer air temperatures were also important predictors of surface water temperatures, with little variation explained by lake morphology. This is the first study to provide limnological evidence for the importance of two large-scale phenomena, global brightening/dimming and global climate change, for lakes worldwide.