Modeling the Impact of Climate Change on Lake Thermal Structure for Small Inland Lakes in the Mid-latitudes

Lakes in the mid-latitudes are subject to large seasonal variations in temperature that have been impacted by climate change. The focus of this study is to determine the impacts of climate change on the thermal structure of small inland lakes in the mid-latitudes. Small lakes comprise more than double the amount of the land surface than large lakes, and have gone largely underrepresented in lakes research regarding climate change. With this knowledge, we can better understand the effects of climate change on small inland lakes’ physical processes and develop more holistic mitigation and management practices for these resources. We identified 517 inland lakes in Michigan based on data availability with surface areas between 0.03 and 81 km², and subdivided this sample into 27 groups based on climate, lake surface area, and trophic state. The F-Lake model was tested using five Wisconsin lakes with varying surface areas and trophic states in two of the climate groups to determine its ability to predict observed lake temperatures. The average root mean squared error for the predicted surface and mean water temperature was 4.8 and 3.8 °C, respectively. We then applied the model to 3 lakes from each of the 27 groups under recently observed and future climate conditions from the regionally downscaled MPI ECHAM5 climate model (A2 emissions scenario) to assess the impacts of climate change on lake thermal structure. We hypothesize that small, eutrophic lakes located in warmer climates will be most strongly impacted, and this represents 20% of the lake resource in our sample. From these results, we will determine the susceptibility of lakes within and among the various climate, size, and trophic classes to the impacts of climate change as well as identify possible threats to aquatic organisms.