July 5 Seiche draws attention on Lake Michigan
07/23
A July 5 seiche on Lake Michigan drew plenty of attention from boaters and fisherman.
Lee Wishau was preparing his catamaran for a sail in the shallows of North Bay when he saw the rock pier he'd fished from for years was completely exposed and a landmark rock - typically under 12 inches of water - cleared the water line by 2 feet.
"I've been going to that beach my whole life," said Wishau of Racine. "That's the first time I've ever been able to walk around the pier without getting wet."
About five minutes later, Wishau said the water gradually came back up, then went out again, but not as drastically. He said he observed several smaller seiches over the next day.
Wishau's observations are backed by data recorded by the National Oceanographic and Atmospheric Administration station in the Lake Michigan waters off Milwaukee. NOAA reported the low-water mark at 4:30 p.m. on July 5.
A seiche is a periodic oscillation of water level caused by an atmospheric disturbance passing over large, confined bodies of water.
The disturbances that cause seiches include the rapid changes in atmospheric pressure with the passage of low or high pressure weather systems, rapidly-moving weather fronts and major shifts in the directions of strong winds.
Although the weather in Racine early on the afternoon of July 5 was pleasant - sunny, 75 degrees with a 10 mph southeast wind - a powerful front had passed through overnight and in the early morning, piling up water on the Michigan side of the lake.
The phenomenon seen by Wishau was part of a massive energy transfer in southern Lake Michigan, raising water levels to the east and creating deadly rip currents. Seven people drowned in the storms of the July 4th weekend on beaches near St. Joseph, Mich.
Small seiches (less than a foot high) are an everyday occurrence on the Great Lakes, according to Dave Schwab, a scientist with the Great Lakes Environmental Research Lab in Ann Arbor, Mich.
But the biggest seiches can clash ships together in harbors, snap mooring lines and swamp fishing boats. Great Lakes history is filled with accounts of large, and occasionally deadly, seiches.
In 1834, during a summer storm, the St. Mary's River at Sault Ste. Marie, Mich. suddenly emptied and, an hour later, filled back up. Local residents flocked into the river bed to catch stranded fish and narrowly escaped the returning surge, according to reports.
More recently, on July 13, 1995, a big Lake Superior seiche left some boats hanging from the docks on their mooring lines when the lake water suddenly retreated. In that seiche, lake water went out and came back within 15 to 20 minutes at Ashland, Wisconsin, Marquette and Point Iroquois, Michigan, and Rossport, Ontario. In just a few minutes, water levels changed about three feet.
And in 1998 a seiche occurred in Two Harbors, Minnesota, that caused several hundred thousand dollars of damage to vessels loading iron ore at the Duluth Missabe Iron Range Railway Company docks. According to published reports, the dock manager said two seiches from 12 to 15 feet were responsible.
According to Noel Pavlovic, ecologist at the Lake Michigan Ecological Research Station in Indiana, seiches are most common on Lake Erie, because of its East-to-West orientation, but do occur frequently on Lake Michigan.
Reported by: Dean Westcott
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