U.S. Water News Online
MARQUETTE, Mich. -- As the research boat bobs up and down
on gray, choppy Lake Superior, Michigan Tech University chemist Noel
Urban and two students drop a metal cylinder over the side to
retrieve a water sample from the bottom.
They are measuring carbon dioxide content -- an unspectacular
statistic by itself, yet an important piece of a highly complex
"It helps us develop a model that can say what's going to happen
as the lake warms up," Urban says.
Plenty of people are wondering the same thing.
Something seems amiss with mighty Superior, the deepest and
coldest of the Great Lakes, which together hold nearly 20 percent of
the world's fresh surface water.
Superior's surface area is roughly the same as South Carolina's,
the biggest of any freshwater lake on Earth. It's deep enough to hold
all the other Great Lakes plus three additional Lake Eries. Yet over
the past year, its level has ebbed to the lowest point in eight
decades and will set a record this fall if, as expected, it dips
three more inches.
Its average temperature has surged 4.5 degrees Fahrenheit since
1979, significantly above the 2.7-degree rise in the region's air
temperature during the same period. That's no small deal for a
freshwater sea that was created from glacial melt as the Ice Age
ended and remains chilly in all seasons.
A weather buoy on the western side recently recorded an "amazing"
75 degrees, "as warm a surface temperature as we've ever seen in this
lake," says Jay Austin, assistant professor at the University of
Minnesota at Duluth's Large Lakes Observatory.
Water levels also have receded on the other Great Lakes since the
late 1990s. But the suddenness and severity of Superior's changes
worry many in the region -- it has plunged more than a foot in the
past year. Shorelines are dozens of yards wider than usual, giving
sunbathers wider beaches but also exposing mucky bottomlands and
"C'mon, girls, get out of the mud," Dan Arsenault, 32, calls to
his two young daughters at a park near the mouth of the St. Marys
River on the southeastern end of Lake Superior. Bree, 5, and
3-year-old Andie are stomping in puddles where water was waist-deep a
couple of years ago. The floatation rope that previously designated
the swimming area now rests on moist ground.
"This is the lowest I've ever seen it," says Arsenault, a lifelong
resident of Sault Ste. Marie in Michigan's Upper Peninsula.
Superior still has lots of water. Its average depth is 483 feet
and it reaches 1,332 feet at the deepest point. Erie, the shallowest
Great Lake, is 210 feet at its deepest and averages only 62 feet.
Lake Michigan averages 279 feet and is 925 feet at its deepest.
Yet along Superior's shores, boats can't reach many mooring sites
and marina operators are begging the U.S. Army Corps of Engineers to
dredge shallow harbors. Ferry service between Grand Portage, Minn.,
and Isle Royale National Park was scaled back because one of the
company's boats couldn't dock.
Sally Zabelka has turned away boaters from Chippewa Landing marina
in the eastern Upper Peninsula, where not long ago 27-foot vessels
easily made their way up the channel from the lake's Brimley Bay. "In
essence, our dock is useless this year," she says.
Another worry -- As the bay heats up, the perch, walleye and
smallmouth bass that have lured anglers to her campground and tackle
shop are migrating to cooler waters in the open lake.
Low water has cost the shipping industry millions of dollars.
Vessels are carrying lighter loads of iron ore and coal to avoid
running aground in shallow channels.
Superior's retreat creates a double whammy in Grand Marais, where
the only deepwater harbor of refuge along a 90-mile, shipwreck-strewn
section of the lake already was filling with sand because of a
Burt Township, the local government, is extending the harbor's
boat launching ramp an additional 40 feet, Supervisor Jack Hubbard
says. Sand and shallow water are choking off aquatic vegetation that
once provided habitat for hefty pike and trout.
Puffing on a pipe in a Grand Marais pub, retiree Ted Sietsema
voices the suspicion held by many in the villages along Superior's
southern shoreline -- Someone is taking the water. The government is
diverting it to places with more people and political influence --
along Lakes Huron and Michigan and even the Sun Belt, via the
"Don't give me that global warming stuff," Sietsema says. "That
water is going west. That big aquifer out there is empty but they can
still water the desert. It's got to be coming from somewhere."
A familiar theory -- but all wet, says Scott Thieme, hydraulics
and hydrology chief with the Corps of Engineers district office in
Detroit. Water does exit Lake Superior through locks, power plants
and gates on the St. Marys River, but in amounts strictly regulated
under a 1909 pact with Canada.
The actual forces at work, while mysterious, are not the stuff of
spy novels, Thieme says.
Precipitation has tapered off across the upper Great Lakes since
the 1970s and is nearly 6 inches below normal in the Superior
watershed the past year. Water evaporation rates are up sharply
because mild winters have shrunk the winter ice cap -- just as
climate change computer models predict for the next half-century.
Yet those models also envision more precipitation as global
warming sets in, says Brent Lofgren, a physical scientist with the
Great Lakes Environmental Research Laboratory in Ann Arbor. Instead
there's drought, suggesting other causes.
Cynthia Sellinger, the lab's deputy director, suspects residual
effects of El Nino, the warming of equatorial Pacific waters that
produced warmer winters in the late 1990s, just as the lakes began
Both long-term climate change and short-term meteorological
factors may be driving water levels down, says Urban, the Michigan
But he and Austin are more concerned about effects than causes.
There's a big knowledge gap about how food webs and other aquatic
systems will respond to warmer temperatures, they say.
"It's just not clear what the ultimate result will be as we turn
the knob up," says Austin, the Minnesota-Duluth professor. "It could
be great for fisheries or fisheries could crash."
That's a question Urban and his colleagues want to help answer
with their carbon dioxide measurements on Lake Superior. Plugging
those and other statistics into comprehensive ecosystem models will
give scientists a basis for making predictions.
"We're always reacting to what's already happened instead of
looking forward," Urban says. "As long as we have a poor
understanding of the basic functions of the lake, we won't be able to
say whether this warming is of major concern or not."
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