Doctoral Dissertation Research: Cosmogenic Surface Exposure Dating of Late Holocene Spatial and Temporal Variability of the Southern Greenland Ice Sheet

博士论文研究：全新世晚期格陵兰冰盖时空变化的宇宙成因表面暴露测年

• 批准号: 1557541
• 负责人: Anders Carlson
• 金额: $ 1.6万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-01 至 2020-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1557541&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Cosmogenic; Surface

This doctoral dissertation research project will examine the behavior of the margins of the southern Greenland ice sheet during the late Holocene epoch, a time period covering the last several thousand years. The doctoral student will seek to determine whether ice margins behaved synchronously in the region and whether they reached their maximum extent before or during the time known as the Little Ice Age from about 1300 to 1900. A more precise determination of when the southern Greenland ice sheet reached its maximum extent will provide new information and insights regarding broader hemispheric climate dynamics. If the southern Greenland ice margins reached their maximum extent during the Little Ice Age at the same time as glacial margins in Europe and North America, then the southern Greenland ice sheet likely behaved in concert with a hemispheric wide climate signal. This finding would suggest that current southern Greenland ice sheet retreat might be in response to warming trends around the globe in recent centuries that are influencing ice retreat in Europe and North America. If the southern Greenland ice sheet reached its maximum before the Little Ice Age, however, a more complex set of explanations for why ice margins in different parts of the Northern Hemisphere reached their maxima during different time periods will be required. Identification of an earlier maximum also would require reconsideration of dynamics affecting the southern Greenland ice sheet itself, because its margins may stabilize in the future as climate models predict minimal warming over this part of Greenland in the coming century. Project findings will be shared more broadly with school groups and the public through education and museum programs. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.The doctoral student will date the retreat of two southern Greenland ice sheet outlet glaciers using cosmogenic surface exposure ages on boulders from moraines that are dated as being more than 300 years in age. `These results will be compared with existing data from a pilot study and new data to the north of these locations. In the end, four different ice margins in southern Greenland will be dated, thereby allowing the testing of spatial and temporal variability in the southern Greenland ice sheet. The student will address two fundamental research questions. (1) When was the late-Holocene maximum of the southern Greenland ice sheet? Regarding this question, the student will test the hypothesis that the late-Holocene maximum underwent a late-Holocene advance more extensive than its Little Ice Age advance in response to significant early cooling. (2) Does regional climate govern southern Greenland ice sheet variability at centennial timescales? The student will address this question by testing the hypothesis that the southern Greenland ice sheet responds synchronously to centennial climate variations, such as those observed during the late Holocene. Testing these hypotheses will shed light on geologically recent ice sheet-climate interactions important for modeling the Greenland ice sheet response to spatially variable temperature changes. Project results will determine if southern GIS margins have responded to climatic changes of less than several degrees on a timescale relevant to humanity?s near-term future, a potentially transformative result, particularly for predicting sea-level rise over the coming century.

该博士论文研究项目将研究格陵兰岛南部冰盖边缘在全新世晚期（涵盖过去几千年的时期）的行为。 博士生将寻求确定该地区的冰缘是否同步变化，以及冰缘是否在大约 1300 年至 1900 年的小冰河时期之前或期间达到最大程度。更精确地确定格陵兰岛南部冰盖何时形成达到最大程度将提供有关更广泛的半球气候动态的新信息和见解。 如果格陵兰岛南部冰缘在小冰河时期与欧洲和北美的冰川边缘同时达到最大范围，那么格陵兰岛南部冰盖的行为可能与半球广泛的气候信号一致。 这一发现表明，目前格陵兰岛南部冰盖的退缩可能是对近几个世纪全球变暖趋势的反应，这些趋势正在影响欧洲和北美的冰退缩。 然而，如果格陵兰岛南部冰盖在小冰期之前达到最大值，则需要一套更复杂的解释来解释为什么北半球不同地区的冰缘在不同时间段达到最大值。 确定较早的最大值还需要重新考虑影响格陵兰岛南部冰盖本身的动态，因为随着气候模型预测下个世纪格陵兰岛这部分地区的变暖程度最小，其边缘可能在未来稳定下来。 项目研究结果将通过教育和博物馆项目与学校团体和公众更广泛地分享。 作为博士论文研究改进奖，该奖项还将为有前途的学生建立强大的独立研究事业提供支持。该博士生将利用巨石上的宇宙成因表面暴露年龄来确定格陵兰岛南部冰盖出口冰川的退缩日期。冰碛的历史可追溯至 300 多年。 “这些结果将与试点研究的现有数据以及这些地点北部的新数据进行比较。最终，将对格陵兰岛南部四个不同的冰缘进行测年，从而可以测试格陵兰岛南部冰盖的空间和时间变化。 学生将解决两个基本研究问题。 (1) 格陵兰岛南部冰盖的全新世晚期最大值是什么时候？ 关于这个问题，学生将检验以下假设：全新世晚期极大期经历了比小冰期提前更广泛的晚全新世提前，以应对显着的早期变冷。 (2) 区域气候是否控制着格陵兰岛南部冰盖在百年时间尺度上的变化？ 学生将通过检验格陵兰岛南部冰盖对百年气候变化同步响应的假设来解决这个问题，例如在全新世晚期观察到的气候变化。测试这些假设将揭示地质上最近的冰盖与气候的相互作用，这对于模拟格陵兰冰盖对空间可变温度变化的响应非常重要。 项目结果将确定南部地理信息系统边缘是否能够在与人类近期未来相关的时间尺度上对小于几度的气候变化做出反应，这是一个潜在的变革性结果，特别是对于预测下个世纪的海平面上升而言。