Thursday, September 03, 2009

Dramatic changes as Lake Michigan rises over two years

Lake Michigan has risen over the past two years. I noticed it the most when we visited Peninsula Point Lighthouse on our vacation to Escanaba this year like we did two years ago. (I wish I would have take a similar picture in July of 2005 on that vacation as well.)

Above is a shot from the top of the Peninsula Point Lighthouse taken on August 26, 2007.

Above is a shot taken from the top of the same lighthouse taken on August 23, 2009. Water now covers a lot of area that was dry land two years ago.

You can tell these are lined up the same way because of the the trees in the foreground and the lighthouse (Minneapolis Shoal Light) in the background on the horizon. I am sure that the great lakes go through these cycles.

Other have noticed the rise in lake levels. Apparently low lake levels mean that cargo ships on the lakes must load less cargo and that raises costs per unit shipped. Every inch of lower lake level means 250 tons less on a 1000ft cargo ship. This adds up.

I went to the NOAA website to look for lake level data. I chose to use the Green bay, WI levels because it appeared to the be the only site with data back to August 2007 when the earlier picture above was taken and you could make the point that Peninsula Point is in Green Bay (which extends from Green Bay to the Upper Peninsula of Michigan).

In answer to a question posed while at the Point, yes, the Great Lakes have tides. You can see the fluctuations in the chart of water levels for July 4th through 6th. The levels change only a few inches due to the tides, but the levels also change due to more important effects like wind and weather. Mostly the Great Lakes experience seiches or slosh.

The next chart shows the verified level data from Jan 2007 through the present. Arrows represent the dates of the two pictures above. There is no verified data for August of 2009 yet but you can see where lake levels were only a month earlier. The difference between Aug 2007 and Aug 2009 is about 1.5 ft which is consistent with the pictures and what I saw at Peninsula Point between the two years.

Lake Michigan has been much higher in recent memory. The plot below goes back to 1995 and shows that the difference between the highest level in the mid 90's and the lowest level two years ago was about 5 ft. You can see shelves of shoreline at Peninsula Point which are consistent with water levels being much higher. Lynn also remembers the Lake Michigan water levels being higher at the family cabin when she was younger.

Some people think that the reason the lake levels have dropped is that dredging of the St. Claire river (which connects Lake Huron to Lake St. Clair, water then goes through the Detroit river to Lake Erie) has opened up a drain hole in the Lake Michigan/Lake Huron system (really one big lake joined by the Straits of Mackinac). There have been many requests for the Army Corps of Engineers to plug this hole.

I suppose that now each time I go to the Upper Peninsula of Michigan, I will need to travel to Peninsula Point and take the same picture since I appear to have accidentally become a historical lake level observer.

1 comment:

Minnesotastan said...

Excellent post. Well researched, well written.