By Jeff Brewer
Tim Fisher, assistant professor of geosciences at Indiana University Northwest, is conducting research that may explain how the most recent ice age ended. Fisher, who has been with IUN since 1994, recently received a research grant from the National Geographic Society to go to Canada and determine the timing and duration of flow through a new lake outlet associated with glacial Lake Agassiz.
This spring, Fisher will travel to Saskatchewan to collect sediment samples for radiocarbon dating. The samples will also be analyzed by IUPUI Geography Professor Catherine Souch, who is interested in the rates of sedimentation and vegetation of the area.
Fisher did his doctoral work on Lake Agassiz while at the University of Calgary. At that time, he established that an additional outlet existed allowing the lake to flow to the Arctic Ocean. The time this outlet was in use coincides with the end of a particularly cold period, known as the Younger Dryas, when the warm water of the North Atlantic Gulf Stream was stopped by ice. Without the flow of warm water, the ice sheets advanced over much of North America and Europe. During this period, a huge flood of water flowed from Lake Agassiz and was deposited into the Arctic Ocean. This catastrophic event would have disrupted the circulation of the polar jet stream forcing it south. This would have the effect of pushing the Gulf Stream north aiding the end of the ice age.
Q. What will your research involve?
A. The work involves going to the northwest outlets of Lake Agassiz in northern Saskatchewan and extracting sediment cores from the bottom of the outlet lake. We'll bring the cores back to the lab and find organisms to be radiocarbon dated.
Q. What do you want to determine?
A. When was the south outlet last open in western Minnesota and when was the northwest outlet last open. When we answer these questions, we can look at the effect of water going south to the Gulf of Mexico and to the north into the Arctic Ocean. An interesting thing is that this Younger Dryas cold period came on fairly quickly and lasted 1,500 years, but it ended over a period of a decade. In fact, looking at ice cores in Greenland, it looks like the weather may have gone from cold to today's climate in a matter of a few years.
One of the biggest questions in science today is what caused that rapid change in global climate? What may have caused it was the opening up of the northwest outlets of Lake Agassiz. We need basic research to find out when these outlets were in use and then we will have a stronger background to look at some of the larger questions of global climate.
Q. What else are you working on?
A. My main love is looking at glacial land forms that develop underneath glaciers. When I've completed my present work, I'll get back to this study. I'll be doing research on drumlins in southern Michigan. It's a mystery what created these land forms. Did they form as result of water flowing underneath the glaciers, similar to what happened in Iceland this past fall when a volcano erupted under an ice cap and a reservoir drained rapidly? Or did drumlins form very slowly in a piecemeal fashion over thousands of years? Through a better understanding of the processes operating under the Laurentide Ice Sheet, which flowed a little south of Indianapolis, a better understanding of our landscape will be gained.
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