DEVELOPING NEW SOURCES OF PROXY CLIMATE DATA FROM HISTORICAL STRUCTURES IN THE LAKE MICHIGAN-HURON BASIN

The need to understand the processes driving lake level variability in the Great Lakes has been underscored over the past decade with record low stands in 2012 followed by a quick shift back to the historic averages in 2014 in the Michigan-Huron basins. These rapid changes have important implications for near-shore ecology, sedimentology, water management, tourism, and industrial commerce throughout the Great Lakes region. Attempts to reconstruct the climatic controls of lake level variability from tree rings have either been based on spatially and temporally limited tree-ring data sets developed in the 1960s and 1970s, or tree-ring records from the Pacific Northwest teleconnected to Great Lakes climate. To date, the necessary tree-ring chronologies to develop more robust reconstructions of climate and its relation to lake level within most Great Lakes basins simply do not exist. A particularly evident gap in available data exists in Lower Michigan, where logging in the 1800s removed most old growth forests. Here we report on efforts to establish new tree-ring chronologies within the Lake Michigan-Huron basin. We developed three species-specific chronologies from a pier near the mouth of the Kalamazoo River that was constructed in 1871. These chronologies resulted in a floating 178-year eastern white pine chronology, an oak chronology tentatively dated to 1636-1862, and an eastern hemlock chronology extending from 1653 to 1862. Crossdating of these records with other regional sites identify a strong summer temperature signal in hemlock growth patterns and a growing-season drought signal in oak growth patterns. These aspects of climate are both important contributors to lake level changes in the Great Lakes. Compared to existing chronologies from Wisconsin, the new chronologies show several periods of similarity in both high-frequency and low-frequency variability, but also several periods of distinctly different growth which indicates that the new chronologies are capturing different climate conditions that could increase the total variation of climate captured in the proxy record.