Thursday, March 22, 2018

Drifting Buoys Track Water Currents in the Great Lakes Straits of Mackinac

Friday, July 27, 2012

by Margaret Lansing, Great Lakes Environmental Research Laboratory

Great Lakes Map

Great Lakes Map

The Straits of Mackinac connect Lake Michigan and Lake Huron. Credit: NOAA
When you’re watching a river or the waves on a lake, do you ever wonder where that water goes? If you threw a rubber ducky into the water, where would it end up? Scientists are studying the movement of water in the Straits of Mackinac, which connect Lake Michigan and Lake Huron, to figure out how the water moves around. This water movement can affect ship traffic, how pollution spreads, and where aquatic animals go.

This summer, NOAA Great Lakes Environmental Research Laboratory (GLERL) and Cooperative Institute for Limnology and Ecosystems Research (CILER) scientists deployed three drifter buoys in the Straits of Mackinac, which experience water currents that are much faster than other areas of the Great Lakes. The buoys drift naturally with currents and transmit their locations periodically via satellite, allowing researchers to track and record their paths in Google Earth. These data will allow scientists to better understand short-term water movements through the Straits.

Drifter Buoy

Drifter Buoy

Captain Mike Taetsch deploys a drifter buoy in the Straits of Mackinac. Credit: NOAA

Over months and years, water travels from Lake Michigan to Lake Huron, flowing downhill towards the ocean. On shorter time scales, hours or days, however, the flow has been shown to switch back and forth between the lakes. These short-term water flows can move about 80,000 cubic meters of water per second (more than the volume of 32 Olympic swimming pools!). This can cause currents of up to 1 meter per second.

GLERL scientists measured currents in the Straits in the 1970s and again in the 1990s, but the present drifters are the first of their kind to be deployed in the area and should help define the sloshing conditions and currents throughout the Straits. A team led by GLERL's Dave Schwab and CILER's Eric Anderson will use the data from the drifters to build and refine a hydrodynamic computer model that links the two Great Lakes for the first time.

Eventually, researchers hope the model will improve the Great Lakes Operational Forecast System and simulate the exchange flow between the two lakes.

“We’re now able to expand our picture of the physical processes in the Straits, and much like the Straits of Gibraltar, the exchange flow between basins provides interesting and complex conditions that can have a dramatic impact on the surrounding environment” said Dr. Schwab.

Hydrodynamic Model

Hydrodynamic Model

Computer model grid of the Straits of Mackinac, as part of the Lake Michigan-Huron hydrodynamic model. Credit: NOAA


Anderson E.J., Schwab D.J., 2012. Oscillating bi-directional exchange flow through the Straits of Mackinac and implications for contaminant transport, Journal of Physical Oceanography, (in review)



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