Satellite Superior: The Sky's the Limit
by Marianne Brokaw
Judy Budd (PhD Biological Sciences,
1997) has oceans of information about Lake Superior; about 280 gigabytes
give or take a byte. In fact, she can—and will—tell you a lot
about any of the Laurentian Great Lakes or the African Great Lakes. But
her work doesn't take her to the far corners of the earth or even onto
water very often.
“I can be sitting in my
laboratory in Houghton and study all five of the Laurentian Great Lakes
on any given day. I look at what can’t be seen from the vantage point
of a ship, only from space.”
As a remote sensing expert,
Budd interprets information provided by one of the many satellites that
circle the earth daily, including meteorological satellites that give
us our weather forecasts and ocean color satellites that provide information
about chlorophyll concentrations in the world’s lakes and oceans.
“Satellites are fundamentally
changing the way we go about studying large-scale systems, such as lakes,”
budd explained. “They are an integral part of all Earth science disciplines,
including geology, forestry and biology. At Tech, we also work with the
physicists and engineers who design and build these space-based instruments,
so all aspects of remote sensing are available.”
Budd’s task, with the
help of other scientists and students, is to interpret voluminous data
into meaningful information about Lake Superior or other lakes under observation.
“Remote sensing gives
us a daily, broad-scale picture of the system, provided cloud cover is
minimal.”
Using satellite data is typical
in ocean studies; what makes the Budd’s work unique is that the information
is adapted for lake study—limnology.
Budd can take archival satellite
data and translate those into meaningful maps of the lakes. Satellite
information must be correlated with ship-based instruments that gather
similar data from the surface. The resulting algorithms will accurately
interpret satellite data for lakes, like estimates of temperature and
surface chlorophyll concentrations. For studying Lake Superior, the satellite
imagery was verified using data from ships and meteorological buoys deployed
around the lake.
So what are these snapshots
of the lake telling us? Lake Superior is a lake that sometimes behaves
like an ocean. For example, phytoplankton (one-celled drifting plants
like algae) in lakes and oceans fix or hold carbon like forests do. It
is the phytoplankton that determine whether Lake Superior is a sink (repository)
or source of carbon to the atmosphere.
Like the ocean, Lake Superior
shows sudden variations in temperature where there might be areas of upwelling
(replacement of surface water by deep cold water) and downwelling (the
opposite effect). In the ocean, upwelling brings nutrient-rich deep water
to the surface and there is a plankton bloom; in Lake Superior, the same
phenomena brings super-cold deep water to the surface, but the ecological
consequences of upwellings in cold and unproductive Superior are still
under study.
“The spatial extent, timing,
and duration of these episodic upwellings would be difficult, if not impossible,
to quantify without the satellite maps."
The Keweenaw Current, a major
system of transport within Lake Superior, is also visible with satellite
maps. It has been studied for more than 100 years by various surface methods,
including throwing bottles off the decks of ships in 1895 and seeing where
they ended up.
But now the current is visible
and can be tracked daily as changes in weather, wind, and temperature
affect its motion, direction, and speed. Sometimes materials caught in
the current are transported up the Keweenaw to the tip and then swirled
south toward the warmer coastal waters of Keweenaw Bay; other times the
wind pushes the current and its contained materials northward into deep
cold Canadian water.
“We are trying to understand
the fate of materials in both the on-shore and off-shore locations.”
One material they have been
able to track is the copper-rich material known as “stamp sand”
that covers the shoreline on several spots in the Keweenaw. Five stamp
mills at Freda/Redridge discharged more than 45 million metric tons of
stamp sands between 1895 and 1922 at the heyday of copper ore processing
in the Keweenaw.
The coarse part of the discharged
material forms black beach sands that now extend about 14 miles north
from their sources and that blanket shallow-water sandy sediments. The
finer particles disperse much farther, moving along the track of the Keweenaw
Current far into the center of the lake. The discharges at Gay formed
black sand beaches that stretch about five miles south to the Traverse
River.
Stamp sand movement affects
not only the aesthetics of the Keweenaw’s white sand beaches but
because it’s toxic to plankton, it can affect the ecosystem of the
lake as well as the nearby land masses.
“We can use the things
we learn about Lake Superior and apply them to other lakes, as well. Similar
remote sensing studies are underway in the African Great Lakes with Canadian
colleagues. There, the problems are also practical in nature, related
to management and protection of the lakes. Among other things, these rift
lakes have terrific problems with increasing sediment loads, over-fishing,
and land-use planning.”
Understanding the way nutrients
and pollutants move around Lake Superior can help solve problems of ecological
imbalance in other lakes. It’s a good lab for limnologists who want
to study basic processes in a relatively clean lake and for oceanagraphers
to study large-scale processes in a smaller, bounded inland sea.
But beyond the science is beauty.
The bird’s-eye view of Lake Superior on Budd’s computer screen
is a work of algorithmic art she calls “a complex mosaic of spatial
and temporal variability.” The images are vivid and varying: colors
ranging from cold blue to fiery orange, indicating changes in water temperature
over space and time—a melding of technology, science, and art. Something
people at Michigan Tech do very well.
For more on the KITES project,
see http://chmac2.chem.mtu.edu/KITES/ ###
This article appeared
in the July 2001 issue of the Michigan Tech Alumnus magazine, Dean
Woodbeck, editor.
kites.html
