The northern cordilleran ice sheet over the last 300,000 years: testing the role of moisture in arctic glaciation

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Climate change continues to be a global priority. Predictive models require reliable, long term, paleoclimate data to evaluate the accuracy of future predictions. The proposed research will provide paleoclimate data from Yukon Territory. A glacier complex termed the northern Cordilleran Ice Sheet repeatedly covered portions of Yukon over the last 2.6 million years. Yukon is unique in Canada because of its glaciated surfaces of great antiquity and large unglaciated area that forms the eastern limit of Beringia. The record of this ice sheet prior to 30 000 years is relatively poorly constrained. Across most of Canada, deposits from the last glaciation cover old glacial surfaces. In contrast, their exposure at the surface in Yukon allows us to use innovative dating techniques (such as Terrestrial Cosmogenic Nuclide exposure dating) to determine the age of the last ice cover. This helps us define periods of colder than present conditions, when glaciers covered much more of the landscape than during the last glacial period. Sediments relating to non-glacial periods located below and on top of these old glaciated surfaces can be examined for plant and insect fossils. By comparing these fossils to their present distribution, the paleoclimate can be estimated. Some of these non-glacial periods were warmer than present and can serve as a good analog for future global warming. In this instance, the past could be the key to the future. These non-glacial sediments can sometime be dated by the presence of volcanic ash beds, similar to what was produced by Mt. St. Helen's. Dating these glacial and non-glacial deposits is the most effective method of determining how climate change affected Yukon for the past 200,000 to 300,000 years.