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GLIN==> Press Release - Great Lakes Temperatures / Water Levels



U.S. Department of Commerce

National Oceanic and Atmospheric Administration

NOAA 99-R518

Jana Goldman
301/713-2483 ext. 181				       	

Great Lakes Temperature Warmer Than Average, NOAA Scientists Say
Lake Levels at 30 year Low

	The relatively warm winters of the past several years set the stage for
the high Lake Michigan water surface temperatures recorded in July, lake
experts at the National Oceanic and Atmospheric Administration said today.

	"Based on the last six years, both 1998 and 1999 are warmer than average,"
said Michael McCormick, an oceanographer at  NOAA's Great Lakes
Environmental Laboratory. 

	As a result of the warmer temperatures the Great Lakes are at a 30-year
low, three to nine inches below their long-term averages, because of lack
of rain and mild winters. While providing wider beaches for swimmers and
those living along the shore, lower water levels are causing problems for
some boat owners who need to seek deeper water for docking and recreational

	Long-term temperature records in the Great Lakes exist at various
municipal water intake points. However, only recently has it been possible
to obtain lakewide measurements of water temperatures. NOAA's Great Lakes
Environmental Laboratory (GLERL) in Ann Arbor, MI, has developed a Great
Lakes Surface Environmental Analysis (GLSEA) that uses satellite-derived
water temperature data.

	Based on 50 years of modeled data which reconstructs temperature data
based on meteorological records, July 1999 is the third warmest year of the
last 50 years for Lake Michigan, following 1998 and 1995. The preceding
winter temperatures of those two years were also warmer than normal.
Inferences on climate changes in the Great Lakes water temperature require
much longer data records, the scientists say.
	Prolonged heat waves and calm conditions can heat up the very near
surfaces and near shore waters. For example, conditions during the past
week have caused the average near surface temperatures in Lake Michigan to
exceed those measured at any time during the last six years. Further
modeling analyses suggest that all the Great Lakes have shown
higher-than-normal monthly water surface temperatures for the past 18 months.

	Because of the large volumes of water and extreme depths, the Great Lakes'
lake-wide temperatures respond slowly to day-to-day shifts in air
temperature and are more representative of seasonal or longer changes in

	The higher than average water temperatures are likely to increase the late
summer and fall evaporation, which will further reduce seasonal water
levels, said Frank Quinn, senior hydrologist at GLERL.

	Lower levels also mean that the lake freighters that carry iron ore, coal,
and limestone between Great Lakes ports such as Duluth, South Chicago, and
Toledo cannot travel fully loaded because of the low water levels in the
harbors and connecting channels.   

	According to the Lake Carriers Association, an organization that
represents U.S. flag vessel operators on the Great Lakes, "Vessels working
the Great Lakes forfeit anywhere from 70 to 270 tons of cargo for each one
inch reduction in loaded draft." The association reports an 8.6 percent
decrease in shipments of iron ore, coal, and stone in April - the most
recent figure available - compared with the same period last year.

	The outlook is for lower levels during the coming fall and winter because
of the normal seasonal decline in water levels, Quinn said.

	NOAA's mission is to describe and predict changes in the earth's
environment and to conserve and manage wisely the nation's coastal and
marine resources.


	For more information on the Great Lakes, visit: http://www.glerl.noaa.gov and

	For Great Lakes shipping information, visit: http://www.lcaships.com

	All NOAA press releases and links to other NOAA material can be found on
the Internet at http://www.publicaffairs.noaa.gov/releases99/.  Journalists
who wish to be added to NOAA's press release distribution list, or who wish
to switch from fax to e-mail delivery can send an e-mail to:
releases@www.rdc.noaa.govor fax to (202) 482-3142.
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