GLIN==> Lake Superior Forecast: Warm Water

For Immediate Release

July 8, 2010

Science Contact: Jay Austin, 218-726-8773,  <mailto:jaustin at d.umn.edu>
jaustin at d.umn.edu

Lake Superior Forecast: Warm Water

Duluth, Minn. - Researchers at the Large Lakes Observatory (LLO) of the
University of Minnesota Duluth predict that the surface of the open waters
of Lake Superior will be exceptionally warm this summer. They suspect that
water temperatures may exceed the high recorded during the strong El Niño
summer of 1998, 68 degrees Fahrenheit (20 degrees Celsius). The average
water temperature of Lake Superior’s surface waters in August is about 59
degrees Fahrenheit (15 degrees Celsius). (It is already about 59 degrees at
NOAA’s Western Lake Superior buoy.)

Jay Austin, associate professor of physics, and his collaborator Steve
Colman, professor of geology, report that this past winter’s low ice
coverage led to an early spring turnover and an early onset of summer
stratification in the world’s largest freshwater lake by surface area.
Early stratification will allow the lake’s surface waters to warm for a
longer time. This year, the lake began forming a warm surface layer in
early- to mid-June rather than the normal mid-July. From now until autumn,
the surface waters will continue to warm and blanket the colder waters. When
Austin noticed that the lake was headed for early stratification, he said
that this “typically means that it's going to be a very warm year in Lake
Superior.” 

Lake turnover happens as the winds “turn over” the lake, mixing the water
column until the water reaches about 39 degrees Fahrenheit (4 degrees
Celsius). At that temperature, the water column begins to “stratify,” where
warmer water forms a layer over the colder waters below. 

Austin and Colman grabbed headlines in 2007 for showing that summer water
temperatures were warming twice as fast as air temperatures over the last 30
years, based on data from NOAA buoys in Lake Superior. The reason for the
warming was partly due to increasing air temperatures, but also strikingly
related to winter ice cover. The less winter ice, the earlier the summer
stratification begins, and the longer the summer heating season for the
surface waters. Austin said, “After watching last winter’s ice cover, I
suspected that Lake Superior was in for warm summer surface water
temperatures as much as five months ago. The early stratification date this
year adds weight to my suspicions.” 

Lake Superior’s warming waters could alter the productivity of microbes and
algae, affect commercial and sport fishing, and create a longer recreational
summer season. Swimmers might rejoice but lake trout may have to move deeper
or further offshore.

 

To learn more about how a changing climate is affecting Lake Superior, visit
Minnesota Sea Grant’s climate portal at: www.seagrant.umn.edu/climate/. For
access to the University of Minnesota Duluth’s meteorological buoy data,
including real-time water column temperature, see:
www.d.umn.edu/~jaustin/buoy_2010.

 

Communications contact:

Nancy Hoene

Communications Coordinator

Minnesota Sea Grant

(218) 726-7677

nhoene at umn.edu

 

 

 

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