The currents of Lakes Michigan and Huron / John C. Ayers.

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Strait, False Detour Channel, and Detour Channel flows westward along the
north shore to about Les Cheneaux Islands. Here it meets the outflow from
Lake Michigan and the two unite and turn southeast. The region of junction of
the two waters is east of Mackinac Island and about north of the east end of
Bois Blanc Island. The united flows move southeastward along the shore of
Michigan's Lower Peninsula to Presque Isle. Just beyond Presque Isle the current leaves shore by continuing to the southeast while the shore trends southward. From Presque Isle to mid-lake at latitude 440 30' the outflow current
is about 15 miles in total width with the strongest currents in the center seven
or eight miles.
In the offing of Thunder Bay the current begins to fan out gradually and
the fanning out continues to mid-lake at 440 30' where the current separates
into two branches. One branch (the smaller one) turns eastward for a few
miles and then curves into a northward direction and enters the mid-lake eddy.
The major portion (the flow-through current) is contained in the branch that
moves west and reaches the Michigan shore throughout the region from Sturgeon
Point to Oscoda.
Flowing southward after reaching the Michigan shore, the flow-through current in part dips into the outer end of Saginaw Bay as far as Big Charity Island and in part crosses directly across the mouth of the bay. At Pointe aux
Barques the current is again narrow and close to shore. From Pointe aux
Barques the flow-through current moves northeast to the center of the lake,
then turns south for about 35 miles. In mid-lake off Harbor Beach the current
curves to the southwest and returns to the Michigan shore. It runs along shore
to Lexington where it turns southeast and moves to the center of the lake and
then curves southwestward. It reaches the St. Clair River as strong flow from
the northeast in the eastern half of the extreme lower end of the lake.
Associated with the flow-through current, and driven gear-wise by it, are
five medium-to-small eddies of current. A clockwise eddy outside Thunder
Bay and a small counterclockwise one in Thunder Bay are the first two of the
five. Off the mouth of Saginaw Bay a medium-sized eddy is formed by the
westward meander of the flow-through current. On the Ontario shore off
Goderich is a counterclockwise eddy driven by the flow-through current. The
final eddy of the five is a small clockwise eddy situated off Lakeport, Michigan.
Returning to mid-lake at 44 30' and the eastward branch of current, we
find that this branch is the chief contributor to the mid-lake eddy. From 440
30' this branch flows successively east, north, northwest, and southwest to
rejoin the eastern side of the flow-through current in the offing of Presque
Isle and thus to circumscribe the mid-lake eddy.
A long flattened clockwise eddy driven by the mid-lake eddy is located
along the Ontario shore from Cape Hurd to Clark Point. At the entrance to
Georgian Bay, waters from this eddy and from the mid-lake eddy pass eastward into the bay. There is some evidence that average surface current in
Owen Channel between Fitzwilliam Island and IManitoulin Island may be westward, but the evidence is not very conclusive and this current is not shown on
the chart.
On 29 June 1954 the east side of the mid-lake eddy showed a reversed-S
of current between latitudes 450 00' and 450 30'. It is doubted that this is a
permanent feature of the eddy. Until this is proven, the east- side of the eddy
should be considered as being approximately parallel to the trend of the Canadian shore.
Along the shores of Manitoulin, Cockburn, and Drummond Islands there are
currents of some strength moving westward parallel to shore. The waters