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

冰川消融期间的快速气候变化与冰盖、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的比较。虽然已经发现了劳伦泰德冰盖变化的一般模式，但它们并没有在亚世纪尺度上得到连续的解决。缺乏具有精确辐射控制的连续、高分辨率陆地冰川年表仍然是理解冰期气候的一个限制因素。这些记录，特别是来自冰盖东南部分的记录，可以提供与北大西洋气候记录（海洋和冰芯）的重要比较，并对冰川活动与气候变化有关的假设进行严格检验。新英格兰Varve年代学的巩固，以及冰川动力学和陆地变化记录的发展，为制定距今1.8万年至1.15万年的完整的年尺度陆地年代学提供了难得的机会。冰阀沉积与冰川融水排放有关，可用于监测冰盖退缩，并与冰川物质平衡和气候直接相关。东南冰盖的进展、冰退缩率和年融水排放量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，它是驱动者还是响应者，或者它是独立的还是有时间滞后的。将阀门年表用作冰川事件（包括可能引发快速气候变化的洪水）的精确区域年表，对于评估气候模式和个别洪水影响海洋环流和气候所需的阈值至关重要。该项目将加入新英格兰Varve年代学序列，形成一个跨越6000年（18.0-11.5 kyr BP）的单一序列。这将是北美陆地冰锋变化、冰退缩率和冰湖历史的最长连续、高分辨率记录。在关键区域收集的岩心将加入现有的阀门年表序列，新的碳-14年龄将用于改进其日历年校准。更广泛的影响：1)新英格兰年代学异常的准确性和精度将证明冰川期年代学在北美其他地区的潜在用途，在这些地区，冰川期序列无论是冰川年代学还是气候记录都没有被研究过。该项目将作为扩展年表以覆盖整个末次冰期（~24-11.5 kyr BP）的垫脚石，并可能促进美国和加拿大许多其他地区的年表研究。2)年表将作为其他测年技术的校准或一致性检验。NEVC代表了最精确和准确的机会，将宇宙成因核素年龄与独立校准的消冰年表进行比较。阀门年代学的改进将极大地提高这种地质校准的准确性和信心。3)结果的传播，除了在科学期刊上正常发表外，还将包括为其他研究人员提供一个血管记录和图像库的互联网可用性；关于如何收集、制定和匹配阀门记录的教学报告；并编制了阀门特性和特征的图像词汇表，供学生和教师参考。这个项目将扩大塔夫茨大学的研究计划。本科生（每年暑期两名，为期三年）将在项目的实地和实验室阶段积极参与研究。每个学生都将在指导下对一个完整的阀门部分进行从头到尾的分析，从而完成为期一年的论文或研究项目。在三年的时间里，该项目将有效地使美国接受冰川岩芯分析培训的人数增加一倍。

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.