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GLERL What's New 1996
NOAA Office of Public
Affairs
National Oceanic and Atmospheric Administration
U. S. Department of Commerce
1996 PRESS RELEASE
Contact: Dane Konop Michael Quigley
(301) 713-2483 (313) 741-2149
Dane.Konop@noaa.gov Michael.A.Quigley@noaa.gov
Scientists on the Trail of Mysterious Lake Michigan Phenomenon
Visible only from a NOAA environmental satellite 450 miles above the lake and first observed in 1980, its exact nature still eludes scientists. But all this may soon change if scientists can successfully plan and carry out studies to determine the precise nature, causes, and potential effects of this mysterious visitor.
According to Brian Eadie, a scientist at NOAA's Great Lakes Environmental Research Laboratory in Ann Arbor, Mich., coordinating the studies, the phenomenon is an extensive, recurrent coastal plume of muddy water that occurs usually after the melting of shore ice and the onset of spring storms. Using a link to NOAA's nationwide CoastWatch network for a frame-by-frame analysis of NOAA satellite images, scientists at the Great Lakes Environmental Research Laboratory have tracked the development and dissipation of the plume from mid-March to late-April of this year. Because water in the plume reflects back more light relative to water elsewhere in the lake, a lighter, detectable outline of the plume could be followed over time. However, while satellite imagery provides a reliable way of monitoring the plume, two big questions still remain: What makes up the plume? Where did it come from? To answer these questions, GLERL and university scientists, together with a helicopter flight crew at the U.S. Coast Guard's Ninth District Air Station in Traverse City, Mich., teamed up to collect samples of the plume's waters by air and sea this past April.
Physical, chemical, and biological analyses by the 13-member scientific group revealed much about the nature of the plume and potential effects on the Lake Michigan food chain. The plume was found to consist of very small clay and silt-sized particles that were most likely carried up into lake waters when spring storms and strong north winds produced high waves and currents that eroded fine material from the southwestern shore of Lake Michigan. Scientists determined that total suspended matter, the concentration of free-floating particles in water, was uniformly higher than that of surrounding waters.
How big was the plume and how much material was carried within it? Scientists estimated it to be as much as 6 miles wide and at least 60 miles long, eventually stretching some 200 miles. Scientists estimated that 300,000 tons of material were transported and eventually deposited on Lake Michigan's southeastern shore. By comparison, the largest (1000-foot) Great Lakes freighters carry a cargo of 70,000 tons, meaning the entire plume would amount to the cargo capacity of about 4.3 of these freighters.
What's the impact of the plume on the ecology of Lake Michigan? Preliminary data on the community of microscopic plants and animals within the plume indicate that conditions there promote biological activity, possibly by providing increased supplies of phosphorus. Added phosphorus contributed by the plume, coupled with spring warming of lake water and increased sunlight may lead to higher overall food chain productivity in those years when the plume develops. In addition, because the tiny clay and silt particles of the plume will readily bind with PCB's or other contaminants in the lake water, the plume phenomenon may represent a natural mechanism that may help strip such harmful contaminants from lake water.
Visible band satellite imagery of southern Lake Michigan. On March 16, the NOAA 12 (morning) AVHRR Channel 1 satellite image shows shore-fast ice along the eastern shore of the southern basin and large ice floes at the south end of the lake. After several days of warming temperatures and strong northerly winds, the March 22 NOAA 14 (afternoon) image shows the presence of a highly reflective plume, appearing to originate along the southwestern shoreline and extending eastward along the southern shore. On April 1, a Coast Guard search and rescue helicopter was used to collect 5 samples from the plume region while our 65' ship was able to collect 1 sample and 2 CTDs further north. A subsequent set of 4 samples and CTDs were collected by small boat on April 10. Sampling locations are marked by crosses. By April 24, the plume extended along the entire eastern shore, but the intensity was considerably diminished. The majority of the western shoreline is composed of erodable silty-clay bluffs (Jibson et al, 1994), while the southern shore is highly industrialized with extensive man-made features. The eastern shore is primarily sandy beaches backed by dunes. The pattern of sediment accumulation is highly asymmetric; the western and southern regions do not accumulate recent sediments, while the highest sediment accumulation in the lake is on the southeastern slope (coincident with the eddy features in the figure) and not in the deep central region. Clouds are masked out on the March 22, April 10, and April 21 images.
6/10/96
Note To Editors:
Satellite images of the Lake Michigan plume can be downloaded from:
http://www.glerl.noaa.gov/news/1996/plume.gif Mar-Apr (GIF fmt)
http://www.glerl.noaa.gov/news/1996/plume96.ps Mar-Apr (PS fmt)
http://www.glerl.noaa.gov/news/1996/plume-apr1.ps Apr 1 (PS fmt)
http://www.glerl.noaa.gov/news/1996/plume-apr10.ps Apr 10 (PS fmt)
All NOAA press releases and links to other NOAA material can be found on the NOAA Public Affairs World Wide Web home page http://www.noaa.gov/public-affairs. If you'd prefer to receive NOAA press releases by electronic mail rather than facsimile, send an e-mail to Jslaff@rdc.noaa.gov.
Last update: September 12, 2002 mbl