Boundary condition controls on the timing and extent of Pleistocene glaciations in Yukon

边界条件对育空地区更新世冰川作用时间和范围的控制

• 批准号: RGPIN-2018-06887
• 负责人: Ward, Brent
• 金额: $ 5.25万
• 依托单位: Simon Fraser University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=751191
• 关键词: Boundary; condition; controls; timing; extent

The CIS was an important component of Earth's past climate system: it responded to orbital induced climate forcing during repeated growth and decay and provided meltwater to adjacent oceans, which can influence climate. Precipitation limited means that glacier extents are mainly controlled by the amount, distribution, timing and type of effective precipitation. These precipitation limited glacier systems are of particular interest in paleoclimate studies because the marine isotope record, commonly used as a proxy for the relative global mass of glaciers, may not accurately reflect all glacier limits. This proposal will focus on the Yukon Territory, which has been repeatedly affected by the northern Cordilleran Ice Sheet (CIS). Although termed an ice sheet, it is better described as an ice complex, comprised of a series of coalescing valley glaciers and piedmont lobes whose ice flow was strongly controlled by topography. This ice complex produced irregular, digitate horseshoe-shaped glacial limits on the plateau area of central Yukon. Many of these ice flows had separate source areas, reflecting differences in the regional accumulation zones and the nature of the underlying topography. This ice complex produced three irregular, mappable, digitate horseshoe-shaped chrono-geomorphic regions on the plateau area of central Yukon ranging in age from 2.6 Ma to 12 ka. These three limits were thought to represent regionally coherent advances of the Cordilleran Ice Sheet. Our work, however, shows that regional ice expansion neither correlates across Yukon nor to peaks in global ice volume. Factors that could explain this varied response of the northern sector of the CIS across time and space will be tested and include changes in local topography, glacier dynamics, and climate. The primary objective of this proposal is to elucidate the varying forcing conditions that affect the extents and timing of Pleistocene glaciation in Yukon. An important dataset required for this objective includes a robust chronology of ice expansion to correlate to the marine isotope record and other similar glacier systems. Yukon is a perfect location to do this as it contains one of the oldest and richest terrestrial records of Arctic Quaternary climate change. With active volcanism, especially the presence of volcanic ashes, there is the potential for numerous dating methods to improve the chronology.My research in Yukon will significantly contribute to our understanding of the roles that climatic and non-climatic factors play in the response of high latitude glacier systems to climate change. Results will have an affect on research in other precipitation limited systems throughout the Arctic. These systems represent an important benchmark for climate models who will use that require data fro this study for validation. Careful study of deglaciation of the CIS also provides one analogue for current ice sheets such as Greenland.

独联体是地球过去气候系统的一个重要组成部分：它在反复生长和衰退期间对轨道引起的气候强迫作出反应，并向邻近海洋提供融化的水，这可能会影响气候。降雨量有限是指冰川范围主要受有效降水量、分布、时间和类型的控制。这些降水量有限的冰川系统在古气候研究中特别令人感兴趣，因为海洋同位素记录通常被用来替代相对全球冰川质量，可能不能准确地反映所有冰川限制。这项提议将把重点放在一再受到北部科迪勒兰冰盖(独联体)影响的育空地区。尽管它被称为冰盖，但更确切地说，它是由一系列汇合的山谷冰川和山前山顶组成的复杂冰川，其冰流受到地形的强烈控制。这个冰川复合体在育空中部的高原地区产生了不规则的马蹄形冰川边界。其中许多冰流有不同的源区，反映了区域堆积区和下伏地形性质的差异。该冰杂岩在育空中部高原地区产生了三个不规则的、可测绘的、数字马蹄形的计时地貌区，年龄从2.6 Ma到12ka不等。这三个极限被认为代表了科迪勒兰冰盖在区域上的一致推进。然而，我们的工作表明，区域冰的扩张既不与育空地区相关，也与全球冰量的峰值无关。可以解释独联体北部在时间和空间上的不同反应的因素将得到测试，其中包括当地地形、冰川动态和气候的变化。这一建议的主要目的是阐明影响育空地区更新世冰川作用程度和时间的不同强迫条件。这一目标所需的一个重要数据集包括一份可靠的冰膨胀年表，以便与海洋同位素记录和其他类似冰川系统相关联。育空是这样做的完美地点，因为它包含了北极第四纪气候变化最古老和最丰富的陆地记录之一。随着活火山作用，特别是火山灰的存在，有可能用许多测年方法来改进年代学。我在育空的研究将极大地有助于我们理解气候和非气候因素在高纬度冰川系统对气候变化的响应中所起的作用。研究结果将对整个北极地区其他降水限制系统的研究产生影响。这些系统代表了气候模型的一个重要基准，这些模型将使用这项研究所需的数据进行验证。对独联体冰川消融的仔细研究也为格陵兰等当前的冰盖提供了一种类似的方法。