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

气候变化仍然是全球的优先事项。预测模型需要可靠的、长期的古气候数据来评估未来预测的准确性。拟议的研究将提供育空地区的古气候数据。在过去的260万年里，被称为北部科迪勒兰冰盖的冰川复合体反复覆盖着育空地区的部分地区。育空在加拿大是独一无二的，因为它有非常古老的冰川表面和大片未冰川区域，形成了贝林贾的东部边界。3万年前的冰盖记录相对较差。在加拿大的大部分地区，最后一次冰川的沉积物覆盖了古老的冰川表面。相比之下，它们在育空地区地表的暴露使我们能够使用创新的测年技术(如陆地宇宙核素暴露测年)来确定最后一次冰盖的年龄。这有助于我们定义比目前状况更冷的时期，当时冰川覆盖的地形比上一次冰川时期要大得多。位于这些古老的冰川表面下方和顶部的与非冰期有关的沉积物可以进行植物和昆虫化石的检查。通过将这些化石与它们现在的分布进行比较，可以估计出古气候。其中一些非冰期比现在更温暖，可以很好地类比未来的全球变暖。在这种情况下，过去可能是未来的关键。这些非冰川沉积物有时可以通过火山灰床的存在确定年龄，类似于山上产生的火山灰床。测定这些冰川和非冰川沉积物的年代是确定气候变化在过去200,000到300,000年来如何影响育空地区的最有效方法。

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.