It was great to help out Dr. Tim Fisher (University of Toledo) in this effort (the full publication is here). Dr. Fisher was vacationing in Georgian Bay on Lake Huron when he discovered a stump rooted ~0.5 below the historical low of 1985. This low stand based on radiocarbon and tree-ring analysis occurred during the late decades of the 1600s. Since Lakes Michigan and Huron are joined at the straits of Mackinaw we can infer that this drop was basin wide. Such a drop today would significantly affect the shipping and shoreline infrastructure of these international water ways.
Figure 1. Map showing the location of the stump in Georgian Bay.
Figure 2. Photographs of the in-place stump.
Figure 3. Dating of the stump is critical and the figure above shows the wiggle-matching of a series of radiocarbon ages with the help of a tree ring sequence. Radiocarbon ages matched to the radiocarbon calibration curve allows for a unique solution to the dating placing the age of tree growth into the late 1600s.
The late 1600s is a fascinating interval in Earth history and has been associated with large-scale changes in the ocean – atmosphere system worldwide. Work by colleagues in Scotland have linked this interval to major societal changes and the Scottish Ills. In the North Pacific our recent Keck Project, examined this interval, which is also associated with large glacier changes and dramatic cooling. The late 1600s climate anomalies and associated dramatic changes is particularly fascinating as we continue into the forecasted super El Niño in 2026-2027.
The Wooster Tree Ring Lab has ongoing efforts to reconstruct the levels of the Laurentian Great Lakes with past efforts resulting from a Wooster Independent Study, and a more recent study reconstructing Lake Erie levels initiated by a junior Independent study. Pending work and publications on Lake Michigan and Huron levels includes the work of Wooster student Lynnsey Delio.
Many thanks to Nick Wiesenberg of the Wooster Tree Ring Lab for his contributions to this work.
Congratulations on the new paper, Tim and Greg. Classic example of serendipity in the discovery-based sciences. It worked because Tim recognized an anomaly and followed up on it. Fortune favors the prepared mind, said Louis Pasteur.