The Younger Dryas climate event is important in earth history because it is a rapid reversal in climate change that occurred without any known, direct external forcing. Thus it is the best example of the earth's internal feedbacks causing climate change. At present, the effects of the Younger Dryas cooling event are poorly known in many parts of the world. The purpose of this research is to determine the timing and climatological effects of this event in Minnesota and Wisconsin. The PI will use annually-laminated lake sediments to precisely date the timing of this vegetation change. Then the PI will evaluate the pollen in the cores to determine the changes in temperature and precipitation that accompanied the climatic event. Given the possibility of internal feedbacks altering the effects of future greenhouse warming, it is important to study this past example in order to better predict future changes in climate.
