[Date Prev][Date Next][Date Index]

E-M:/ Lake St Clair -- Standing Waves?



EMers,

I was recently reviewing this image: http://earthobservatory.nasa.gov/Newsroom/NewImages/Images/detroit_L7_20011211_lrg.jpg

(This enhanced true-color image of Detroit was acquired in the spring of 2001 by the Enhanced Thematic Mapper plus (ETM+) aboard NASA’s Landsat 7 satellite.)

 

In the process of working with the image, I was drawn to the streamline patterns along the shores of Lake St. Clair. Presumably the near-shore lighter colored areas represent a combination of biologic activity coupled with sediment transport from feeder streams. However, I found it fascinating that there were streamlines aligned on an east-west axis that seemed to be associated with a set of (apparently) semi-circular standing waves about 3-miles long, starting south of the St Clair Cutoff Channel, roughly aligned with 11-Mile Rd (696).

 

The streamlines are interesting but aren't particularly surprising when you consider how mixing occurs in a large body of water. What I'm particularly interested in is the (apparent) standing waves. It is almost a mile between crests (or troughs, or is it just changes in water clarity?)  What is causing the "waves" to form? Could the waves be the result of oscillations derived from a seich? If we assume 1-mile between crests coupled with a flow velocity of 1-mile per hour, that suggests the lake is surging back and forth (north-south) once per hour. Alternatively, is there something about the geometry at the mouth of the Cutoff Channel that causes a pulsed flow?

 

Another guess at the cause of the waves depends on the several outlets that cross the St Clair Delta. Is it conceivable that Anchor Bay is acting as a resonator that modulates flow from each of the cross-delta channels? If that was the case, then I'd expect to see standing waves proximate to other channels across the delta, not just off the Cutoff Channel.

 

You may have to adjust the color settings on your monitor to enhance the resolution of the various streamlines and waves. I eventually used an image processor to build greater contrast than what is present in the original image.

 

My root question is; Has anybody seen other photos of this phenomonum? Any other explanation for the causitive mechanism? The waves are forming in an area where the lake is approaching its greatest depth – are they subsurface waves like at the Straits of Gibraltr.

 

-Tim-

 

Timothy Carpenter, P.E., Pres.,
GeoDynamics Consultants, Inc.
5043 Whitlow Ct.
Commerce Twp., Mi 48382
248-363-4529 (voice & fax)
248-766-1629 (cell)
geodynamics@comcast.net (primary)
geodynamics@att.net (secondary)