Animated Map of Current in the Great Lakes

Link to Currents in the Great Lakes from NOAA

Rip tides in the Great Lakes

This is what a rip current looks like in the Great Lakes.  If you are going to swim in the Great Lakes know that something rolling in like this will be very difficult to get out of.  If you do get caught, swim parallel to the shore.  You can't fight against this strong current.

The photo was created by NOAA.

Water Levels in the Great Lakes: NOAA Information

The information below is from the NOAA educational website.  The photo is on the cover of my book, The Dynamic Great Lakes.  The scene is an alvar on the Bruce Peninsula in Canada on Lake Huron.

"Water levels in the Great Lakes change because of meteorological effects, not tides.

Water levels in the Great Lakes have long-term, annual, and short-term variations. Long-term variations depend on precipitation and water storage over many years. Annual variations occur with the changing seasons. There is an annual high in the late spring and low in the winter. These changes occur at a rate that can be measured in feet per month.

True tides, changes in water level caused by the gravitational forces of the sun and moon, do occur in a semi-diurnal (twice daily) pattern on the Great Lakes. Studies indicate that the Great Lakes spring tide, the largest tides caused by the combined forces of the sun and moon, is less than five centimeters (two inches) in height. These minor variations are masked by the greater fluctuations in lake levels produced by wind and barometric pressure changes.

Consequently, the Great Lakes are considered to be essentially non-tidal.

For more information:

Center for Operational Oceanographic Products and Services

Great Lakes Water Level Data

Great Lakes Online

Tide Predictions and Data Frequently Asked Questions

Tides Tutorial, NOS Education

What are Tides? - Diving Deeper audio podcast "

Lake Superior Frozen

This satellite photo shows Lake Superior on March 3, 2010.  The lake is frozen due to the cold winter. 

According to NOAA, Lake Superior rarely freezes over completely and then just for a few hours.  Complete freezing occurred in 1962, 1979, 2003, 2008, 2009 and this year.

Read more about ice on the Great Lakes in The Dynamic Great Lakes.

NOAA Chart showing depths of Lake Michigan

Lake Michigan's depths: red shallow, dark blue the deepest part.  Lake Michigan is divided into two basins.  Where you see a change from green to dark blue shows the two basins.  It takes 99 years for the water to circulate out of Lake Michigan from the south to the north.  That's why it is important to keep pollutants out of the Lake.  Read more about the circulation of water and more in my book, The Dynamic Great Lakes available in bookstores and on line at Amazon.com and Barnes & Noble as well as many other venues.

Sinkholes on the bottom of Lake Huron

Here are the Great Lakes, the deepest, coldest and farthest north, Lake Superior;  then Lake Michigan the only Great Lake entirely within the U.S. then Lake Huron, shallow Lake Erie and Lake Ontario.

NOAA has mapped their depths.

Here is how the Great Lakes look from outer space. These five freshwater lakes are always changing. That is why I entitled my book, The Dynamic Great Lakes.

To learn more about the Great Lakes and their ecosystems order the book from Amazon.com, Barnes & Noble or the publisher at 1-301-695-1707.