UMD News Releases

UMD Researcher Continues Study of Early History of Lake Superior
with Climate Histories from Regions all Over the World

The earth was just coming out of an ice age 9,300 years ago when a cataclysmic event occurred that plunged the planet into a "cold snap" that lasted for a century or more. Scientists have long suspected that water melted from snow and ice and introduced into the North Atlantic Ocean was the cause — but the source and volume were a mystery. Now, an important new study led by researchers at the University of Minnesota Duluth (UMD) has pinpointed the source.

Professor Steve Colman

UMD postdoctoral researcher Dr. Shiyong Yu (now at Tulane) conducted this significant research study. Dr. Yu was supervised by UMD Professor Steve Colman of the Dept. of Geological Science and the Large Lakes Observatory. UMD graduate student Andy Breckenridge also participated in the study, along with a number of scientists from other universities. The research team raised cores from several small lakes on the Upper Peninsula of Michigan and the Sibley Peninsula of Ontario, Canada.

The study was published in the June 4 issue of the prestigious Science, the world's leading journal of scientific research. Dr. Yu and his co-authors say that a natural dam on the southeast corner of Lake Superior breached, triggering a massive flood.

By dating the age of separation of small basins from Lake Superior as lake level fell during the flood, Dr. Yu and his research team determined the amount, timeframe, and pathway of this flood. Rapidly — perhaps in a matter of months — Lake Superior dropped 45 meters as its waters spilled through southern Canada to the ocean, raising sea level slightly and dropping temperatures worldwide.

"The ocean circulation might be more sensitive to freshwater perturbation than we thought before," says Dr. Yu. "Today, we are quite concerned about global warming. The accelerated melting of the Arctic ice pack could potentially slow the ocean circulation and push the Earth into a cold snap in a similar manner."

The study is part of continuing efforts by UMD Professor Colman and others to understand the early history of Lake Superior. The research group at the Large Lakes Observatory at UMD is working on reconstructing climate history from regions all over the world.