J. Elmo Rawling III, a geomorphologist at the Wisconsin Geological and Natural History Survey, studies the dunes and beaches of Lake Michigan. He wants to know what made lake levels change in the past – so we can understand and predict changes to expect in the future.
“Tree rings help us understand past climates but our supply of old growth trees is limited. Most forests in the upper Midwest were cut down or rotted away,” Dr. Rawling said.
Rawling and his colleagues have found a unique source of tree rings near the western shore of Lake Michigan in an old abandoned pier. In 1791, trees that were about 150 years old were cut down and used to build the Saugatuck, Michigan pier. The rings extracted from the pilings in that pier will give these scientists a picture of the climate back into the 1600s.
“The water level of Lake Michigan has changed, forming or eroding beaches, in the time frame of this study. We want to know what controls those changes and especially how they impact the shoreline,” Elmo said.
The wood at Saugatuck was incredibly well preserved white oak and red pine. If these samples provide useful data, there are other similar structures in places like the Old Peshtigo Harbor that could also be sampled to fill in the climate picture.