Roland Drayson

Professor Emeritus, Atmospheric Science

University of Michigan

The shoreline of Lake Michigan gradually changed, for a number of reasons. The lake level was not constant, partly due to the formation of new outlets for the water to flow out of the lakes and partly because the land slowly rose up, freed of the burden of the thick ice sheets. As evidence, geologists have located beaches that are now distant from the modern shore.

The action of waves served to smooth the shoreline. For example, Sleeping Bear Point at one time extended further into the lake and landslides were common and are still continuing today, as they are also at Pyramid Point to the north. Conversely, sand and gravel was carried by currents and deposited in the more sheltered areas, such as Sleeping Bear Bay.

The water level of the smaller lakes changed; many, including Glen Lake, were originally connected to Lake Michigan, but when its level dropped they became disconnected. The site of the village of Glen Arbor was initially under water, but the combination of falling lake levels and deposition left it high and dry. The same is probably true of the spot where the National Park Visitor Center now stands.

In time, the moraine became covered with vegetation. Good examples are the forested hills surrounding Glen Lake, including the prominent Alligator Hill, a favorite hiking destination for many visitors. However, some of the more exposed areas resisted forestation and are to this day locked in a battle between the drifting sands and the vegetation that is trying to establish a foothold. A trip along the Pierce Stocking Scenic Drive will expose you to both types of terrain. The dunes themselves are perched dunes that are sitting atop the moraine. A prime example is the Sleeping Bear itself. It was formed when vegetation slowed the drifting sand and gradually built up a sizable mound. Today it sits on the edge of an eroding bluff, which, together with the action of humans walking over fragile vegetation, has allowed the wind to blow out a large chunk of the center, exposing the trunks of long buried trees.

Since so many of the features that draw us to the Sleeping Bear Dunes National Lakeshore owe their existence to the global change that brought the last ice age to an end, it is pertinent to ask what lies ahead. It is certain that global warming is taking place now and that most of it is caused by the increase of greenhouse gases, principally carbon dioxide, but also methane, nitrous oxide, etc. The global average temperature has risen about 1^oF over the last century, more over land and more at high latitudes, with most of the increase over the last 25 years. I believe that the rise at Sleeping Bear is likely to be between 5 and 10^oF by the year 2100. The warming will bring many other changes. For example, we can expect changes in precipitation in the area, with more in winter and about the same or somewhat less in summer. Extreme weather will be more common, with more summer rain coming in deluges. Coupled with the increased evaporation due to the warmth, severe droughts will occur more often.

The effect on the local ecosystem will be devastating. Unlike earlier warmings, the changes will be very rapid, giving little time to adapt to the evolving climate. Some creatures may be able to migrate to the north, but plants and trees will be stuck in place and many will eventually die out, presumably to be replaced by exotics. The full consequences are as yet unknown, but they are hardly likely to result in a better Sleeping Bear.

Contrary to what you may sometimes hear or read, the present global warming is an established fact and the overwhelming consensus of scientists is that it is mostly due to greenhouse gases. That scientific debate is over and research is moving on to narrow down the magnitude of the changes, their consequences and ways to mitigate their effects. These changes are not limited to Leelanau and Benzie Counties, but will have important economic and political repercussions throughout the world.

Our thanks to Roland Drayson for submitting the lead article for the “Drifting Sands” this year. Roland recently joined the Board of the Friends of Sleeping Bear Dunes and has been a long time member of our group. He is Professor Emeritus of Atmospheric Science at the University of Michigan. He and his wife have a home on Glen Lake. Ed.

Kerry Kelly

Empire Area Museum D.H.Day Display
Dave Taghon

Crystal River. Photo taken from Dunn's Farm Rd. by Kerry Kelly, 2007