Consolidation and Calibration of the New England Varve Chronology (NEVC): An Annual Continental Record of Ice Dynamics and Terrestrial Change, 18-11.5 kyr BP

新英格兰 Varve 年表 (NEVC) 的合并和校准：冰动力和陆地变化的年度大陆记录，18-11.5 kyr BP

• 批准号: 0639830
• 负责人: John Ridge
• 金额: $ 33.88万
• 依托单位: Tufts University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-04-01 至 2010-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0639830&HistoricalAwards=false
• 关键词: Consolidation; Calibration; New; England; Varve

Rapid climate change during deglaciation is linked to interactions between the ice sheet, the ocean, and the atmosphere. Understanding these interactions requires high resolution comparisons of climate and continental ice. Although general patterns of Laurentide Ice Sheet variation have been found, they are not continuously resolved at a sub-century scale. This lack of continuous, high-resolution terrestrial glacial chronologies with accurate radiometric controls continues to be a limiting factor in understanding deglacial climate. Such records, especially from the southeastern sector of the ice sheet can provide critical comparisons to N. Atlantic climate records (marine and ice core) and a rigorous test of hypotheses linking glacial activity to climate change.Consolidation of the New England Varve Chronology, and the development of records of glacier dynamics and terrestrial change, is a rare opportunity to formulate a complete, annual-scale terrestrial chronology from 18,000 -11,500 years before present. Glacial varve deposition, which is linked to glacial meltwater discharge, can be used to monitor ice sheet retreat and has a direct tie to glacier mass balance and climate. Complete records of readvances, ice recession rates, and annual meltwater discharge of the southeastern ice sheet could be compared to climatic events in the N. Atlantic region to determine whether the ice sheet was in lock-step with climate and ice rafting events, whether it was a driver or responder, or whether it behaved independently or with time lags. The varve chronology's use as a precise regional chronology of glacial events, including floods that may have been triggers for rapid climate change, would be critical to evaluating climate models and the thresholds necessary for individual floods to influence ocean circulation and climate.The project will be to join sequences of the New England Varve Chronology, forming a single sequence spanning over 6000 years (18.0-11.5 kyr BP). This will be the longest continuous, high resolution record of terrestrial ice front changes, ice recession rates, and glacial lake history in North America. Cores will be collected in critical areas to join existing sequences of the varve chronology and new Carbon-14 ages will be used to improve its calendar-year calibration.Broader impacts:1) The exceptional accuracy and precision of the New England Varve Chronology will demonstrate the potential usefulness of glacial varve chronology in other regions of North America where glacial varve sequences have not been studied for either their glacial chronologies or climate records. This project will serve as a stepping stone to an expansion of the chronology to cover the entire last deglaciation (~24-11.5 kyr BP) and is likely to stimulate varve studies in many other regions of the United States and Canada. 2) Varve chronology will serve as a calibration or consistency test of other dating techniques. The NEVC represents the most precise and accurate opportunity for comparison of cosmogenic-nuclide ages for deglaciation with an independently-calibrated deglacial chronology. Refinement of the varve chronology will dramatically improve the accuracy and confidence in this geological calibration.3) Dissemination of results, in addition to normal publication in scientific journals, will include internet availability of a library of varve records and images for other researchers; instructional presentations on how to collect, formulate, and match varve records; and an image glossary of varve characteristics and features as a reference for students and instructors.4) This project will expand the research program at Tufts University. Undergraduates (two per summer for three years), will be active research participants in field and laboratory phases of the project. Each student will be supervised through a start-to-finish analysis of a complete varve section leading to a year-long thesis or research project. Over three years the project will effectively double the number of people in the United States trained in the analysis of glacial varve cores.

冰消期间气候的快速变化与冰盖、海洋和大气之间的相互作用有关。了解这些相互作用需要对气候和大陆冰进行高分辨率比较。尽管已经发现了劳伦太德冰盖变化的一般模式，但它们并没有在亚世纪范围内持续得到解决。缺乏连续、高分辨率的陆地冰川年表和精确的辐射控制仍然是了解冰消气候的限制因素。这些记录，特别是来自冰盖东南部的记录，可以提供与北大西洋气候记录（海洋和冰芯）的关键比较，并对冰川活动与气候变化之间的假设进行严格检验。新英格兰瓦尔夫年表的整合，以及冰川动力学和陆地变化记录的发展，是制定完整的、年度规模的18,000 -11,500年前陆地年代学的难得机会 展示。冰川水沉积与冰川融水排放有关，可用于监测冰盖退缩，并与冰川质量平衡和气候有直接联系。东南冰盖的重新推进、冰退缩率和年度融水排放的完整记录可以与北大西洋地区的气候事件进行比较，以确定冰盖是否与气候和冰漂流事件同步，是否是驾驶员还是响应者，或者是独立行为还是有时间滞后。将 varve 年表用作冰川事件（包括可能引发快速气候变化的洪水）的精确区域年表，对于评估气候模型以及个别洪水影响海洋环流和气候所需的阈值至关重要。加入新英格兰 Varve 年表的序列，形成跨越 6000 多年（18.0-11.5 kyr BP）的单一序列。这将是北美陆地冰锋变化、冰退缩率和冰川湖历史的最长连续、高分辨率记录。将在关键区域收集核心，以加入 Varve 年表的现有序列，并且新的 Carbon-14 年龄将用于改进其日历年校准。更广泛的影响：1) 新英格兰 Varve 年表的卓越准确性和精密度将证明北美其他地区的冰川 varve 年代学的潜在用途，这些地区的冰川 varve 序列尚未对其冰川年代或气候记录进行研究。该项目将作为扩展年代学的垫脚石，以涵盖整个末次冰消期（距今 24-11.5 kyr），并可能刺激美国和加拿大许多其他地区的巨藻研究。 2) Varve年代学将作为其他年代测定技术的校准或一致性测试。 NEVC 代表了用独立校准的冰消年表比较消冰期的宇宙成因核素年龄的最精确和准确的机会。 varve年代学的细化将极大地提高这种地质校准的准确性和可信度。3）除了在科学期刊上正常发表之外，结果的传播还将包括为其他研究人员提供varve记录和图像库的互联网可用性；关于如何收集、制定和匹配 Varve 记录的指导演示；以及 varve 特征和特征的图像词汇表，供学生和教师参考。4) 该项目将扩大塔夫茨大学的研究项目。本科生（三年内每年夏天两名）将成为该项目现场和实验室阶段的积极研究参与者。每个学生都将接受对完整的 varve 部分的从头到尾的分析，从而完成为期一年的论文或研究项目。三年内，该项目将有效地将美国接受冰川岩心分析培训的人数增加一倍。