EAGER: Refining glacial lake history in Taylor Valley, East Antarctica with alternative geochronometers

EAGER：利用替代地质计时仪完善南极洲东部泰勒谷的冰川湖历史

• 批准号: 1946326
• 负责人: Peter Doran
• 金额: $ 4.53万
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1946326&HistoricalAwards=false
• 关键词: EAGER; Refining; glacial; lake; history

Correlating ecosystem responses to past climate forcing is highly dependent on the use of reliable techniques for establishing the age of events (dating techniques). In Antarctic dry regions (land areas without glaciers), carbon-14 dating has been used to assess the ages of organic deposits left behind by ancient lakes. However, the reliability of the ages is debatable because of possible contamination with "old carbon" from the surrounding landscape. The proposed research will attempt to establish two alternate dating techniques, in situ carbon-14 cosmogenic radionuclide exposure dating and optically stimulated luminescence (OSL), as reliable alternate dating methods for lake history in Antarctic dry areas that are not contaminated by the old carbon. The end goal will be to increase scientific understanding of lake level fluctuation in the lakes of Taylor Valley, Antarctica so that inference about past climate, glacier, and ecosystem response can be inferred. The results of this study will provide a coarse-scale absolute chronology for lake level history in Taylor Valley, demonstrate that exposure dating and OSL are effective means to understand the physical dynamics of ancient water bodies, and increase the current understanding of polar lacustrine and ice sheet responses to past and present climatic changes. These chronologies will allow polar lake level fluctuations to be correlated with past changes in global and regional climate, providing information critical for understanding and modeling the physical responses of these environments to modern change. This research supports a PhD student; the student will highlight this work with grade school classes in the United States.This research aims to establish in situ carbon-14 exposure dating and OSL as reliable alternate (to carbon-14 of organic lake deposits) geochronometers that can be used to settle the long-disputed lacustrine history and chronology of Taylor Valley, Antarctica and elsewhere. Improved lake level history will have significant impacts for the McMurdo Dry Valleys Long Term Ecological Research (MCM LTER) site as the legacy of fluctuating lake levels of the past affects the distribution of organic matter and nutrients, and impacts biological connectivity valley-wide. This work will provide insight into the carbon reservoir of large glacial lakes in the late Holocene and have implications for previously reported radiocarbon chronologies. OSL samples will be analyzed in the Desert Research Institute Luminescence Laboratory in Reno, NV. For the in situ carbon-14 work, rock samples extracted from boulders and bedrock surfaces will be prepared at Tulane University. The prepared in situ carbon-14 samples will be analyzed at the National Ocean Sciences Accelerator Mass Spectrometry laboratory in Woods Hole, MA. The two datasets will be combined to produce a reliable, coarse scale chronology for late Quaternary lake level fluctuations in Taylor Valley.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

将生态系统的反应与过去的气候强迫联系起来，高度依赖于使用可靠的技术来确定事件的年龄(测年技术)。在南极干旱地区(没有冰川的陆地地区)，碳14测年被用来评估古代湖泊留下的有机沉积物的年龄。然而，年龄的可靠性是值得商榷的，因为可能会受到来自周围景观的“旧碳”的污染。这项拟议的研究将尝试建立两种替代测年技术，即原位碳-14宇宙成因放射性核素暴露测年和光刺激发光(OSL)，作为南极干旱地区没有被旧碳污染的湖泊历史的可靠替代测年方法。最终目标将是增加对南极洲泰勒谷湖泊湖面波动的科学了解，以便推断过去的气候、冰川和生态系统反应。这项研究的结果将提供泰勒河谷湖泊水位历史的粗略绝对年代学，表明暴露测年和OSL是了解古水体物理动力学的有效手段，并增加了对极地湖泊和冰盖对过去和现在气候变化的响应的当前理解。这些年表将允许极地湖泊水位波动与全球和区域气候过去的变化相关联，提供对理解和模拟这些环境对现代变化的物理反应至关重要的信息。这项研究支持一名博士生；该学生将在美国的小学课堂上突出这项工作。这项研究的目的是建立原位碳14暴露测年和OSL作为(有机湖泊沉积物的碳14的可靠替代)地质计时学，可以用来解决长期以来有争议的泰勒谷、南极洲和其他地方的湖泊历史和年代学。改善的湖面历史将对麦克默多干谷长期生态研究(MCM LTER)遗址产生重大影响，因为过去湖面波动的影响影响了有机质和营养物质的分布，并影响了整个山谷的生物连通性。这项工作将提供对晚全新世大型冰川湖泊碳库的洞察，并对以前报道的放射性碳年代学有影响。OSL样品将在内华达州雷诺的沙漠研究所发光实验室进行分析。对于现场碳14工作，从巨石和基岩表面提取的岩石样本将在杜兰大学准备。现场制备的碳14样品将在马萨诸塞州伍兹霍尔的国家海洋科学加速器质谱仪实验室进行分析。这两个数据集将结合在一起，为泰勒谷晚第四纪湖泊水位波动产生可靠的、粗略的年表。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。