Collaborative Research: P2C2--Synchronizing the North American Varve Chronology and the Greenland Ice Core Record Using Meteoric 10Be Flux

合作研究：P2C2——使用流星 10Be 通量同步北美 Varve 年代学和格陵兰冰芯记录

• 批准号: 1103381
• 负责人: Paul Bierman
• 金额: $ 12.54万
• 依托单位: University of Vermont & State Agricultural College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-15 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1103381&HistoricalAwards=false
• 关键词: Collaborative; Research; P2C2; Synchronizing; North

Non-technical The North American Varve Chronology (NAVC) is a nearly 6000-year-long sequence of annual sediment layers that was deposited in glacial lakes adjacent to the margin of the Laurentide Ice Sheet, which covered much of North America during the last ice age. At the time these sediments were deposited, between approximately 12,500 and 18,000 years ago, climate was warming and the Laurentide Ice Sheet was shrinking rapidly. The sediments that make up the NAVC are an annually resolved record of events that took place at the retreating ice margin, including the position and retreat rate of the ice margin, the flux of water derived from summer melting of the ice sheet, and large glacial-lake outburst floods that occurred periodically as ice-marginal lakes drained. The goal of this proposal is to understand the relationship of these events to climate changes that were occurring at the same time and are recorded in ice core records from Greenland, which is important because i) it will help to understand how large ice sheets responded to rapid climate warming, and ii) because this time period is a potential analog for the current period of rapid warming and likely shrinkage of glaciers and ice sheets. The obstacle to comparing the NAVC with Greenland climate records is that, although both records have been independently dated, the precision of these dates is a few hundred years, which is not precise enough to accurately determine which climate changes are related to which glacial events. This project will try to resolve this issue by comparing records of atmospherically-produced Beryllium-10 in both NAVC sediments and Greenland ice cores. Be-10 is a naturally occuring rare isotope of Beryllium that is created by cosmic-ray bombardment of the upper atmosphere and falls to earth in precipitation. Be-10 production changes through time due to changes in the Earth's magnetic field, and these changes occur everywhere on Earth at the same time. Be-10 is captured and preserved in sedimentary archives such as ice cores and lake sediments. Thus, Be-10 concentrations in the Greenland ice cores and in the NAVC lake sediments should show the same pattern of changes. By aligning these changes with each other, we can place the two records on a common timescale. Thus, even if we do not know the exact time that a particular climate change recorded in the Greenland ice cores took place, we will know exactly what ice-marginal events recorded in NAVC sediments were occurring at that time. We anticipate that we will be able to match these two records with a precision of several decades, which should be precise enough to determine the relationship between important climate changes and ice sheet change.TechnicalThe North American Varve Chronology (NAVC) is a 5659-year-long sequence of annually laminated sediments (?varves?) deposited in lakes adjacent to the retreating Laurentide Ice Sheet (LIS) in eastern North America. It is an annually resolved record of ice-marginal position, meltwater and sediment flux, and proglacial lake outburst floods between ca. 12,500 and 18,000 years ago. The goal of this project is to correlate this varve chronology with contemporaneous climate records derived from the Greenland ice cores. This is important because such a correlation would reveal the temporal relationship between terrestrial ice-marginal events and North Atlantic climate changes, which in turn would shed light on unresolved aspects of late-glacial ice sheet-climate interactions including, for example, i) the effect of proglacial lake outburst floods at the margin of the LIS on North Atlantic climate , ii) the effect of North Atlantic climate on surface ablation and retreat of the southeastern margin of the LIS, and iii) the apparent conflict between sustained cold climate in Greenland and significant ice margin retreat during this time period. The team proposes to correlate these two records at decadal precision, independently of the absolute dating of each of the records, by comparing records of atmospherically-produced (?meteoric?) Be-10 fallout in Greenland ice cores and NAVC sediments. A decadal-resolution record of Be-10 flux to the Greenland ice cores already exists. Here we propose to carry out corresponding Be-10 measurements in varved sediments of the NAVC to i) determine whether or not Be-10 concentrations in these sediments record changes in Be-10 fallout, and ii) if so, generate a record of Be-10 fallout flux comparable to the existing ice-core record so that the two can be correlated.

非技术北美杂志年年表（NAVC）是一个近6000年的年度沉积物层，该层沉积在冰川冰盖边缘附近的冰川湖泊中，在最后一层冰上覆盖了北美大部分地区年龄。在这些沉积物沉积的时候，大约在12500至18，000年前，气候变暖，而劳伦特冰盖迅速收​​缩。构成NAVC的沉积物是每年在撤退的冰边缘发生的事件记录的记录，包括冰缘的位置和撤退速率，源自冰盖的夏季熔化的水通量和大冰川 - 随着冰界湖泊的排水，湖爆发发生了定期发生的洪水。 该提案的目的是了解这些事件与同时发生的气候变化的关系，并记录在格陵兰岛的冰核记录中，这很重要，因为i）将有助于了解大型冰纸如何回应快速气候变暖，ii），因为这段时间是当前快速变暖的时期和冰川和冰盖的可能收缩的潜在类似物。将NAVC与格陵兰气候记录进行比较的障碍是，尽管这两种记录都是独立的，但这些日期的精度为几百年，这还不够精确，无法准确确定哪些气候变化与哪些冰川事件有关。 该项目将试图通过比较NAVC沉积物和格陵兰冰核中大气产生的铍-10的记录来解决此问题。 BE-10是一种自然存在的稀有铍同位素，是由于宇宙射线对高层大气而产生的，并在降水中跌至地球。由于地球磁场的变化，BE-10的生产随时间变化，并且这些变化同时发生在地球上。 BE-10被捕获并保存在冰芯和湖泊沉积物等沉积档案中。因此，格陵兰冰块和NAVC湖沉积物中的BE-10浓度应显示出相同的变化模式。通过彼此对齐这些更改，我们可以将两个记录放在一个共同的时间表上。因此，即使我们不知道格陵兰冰块中记录的特定气候变化发生的确切时间，我们也会确切知道当时正在发生NAVC沉积物中记录的冰界事件。我们预计我们将能够以几十年的精度匹配这两个记录，这应该足够精确以确定重要的气候变化与冰盖变化之间的关系。技术北美瓦尔夫（NAVC）是5659年 - 每年的层压沉积物（？varves？）的长时间序列沉积在北美东部撤退的劳伦德冰盖（LIS）附近的湖泊中。这是每年解决的冰界位置，融化和沉积物通量的记录，以及大约之间的前冰湖爆发洪水泛滥。 12,500和18，000年前。该项目的目的是将这一文献的年代与从格陵兰冰核获得的同时气候记录相关联。这很重要，因为这样的相关性将揭示陆地冰界事件与北大西洋气候变化之间的时间关系，这反过来又揭示了晚期冰川冰原气候相互作用的未解决方面北大西洋气候在LIS边缘的前沿湖爆发洪水泛滥的影响，ii）北大西洋气候对LIS东南边缘的地面消融和撤退的影响，以及III）明显的寒冷气候之间的冲突并在此期间大量的冰缘撤退。该团队提议通过比较格陵兰冰芯和NAVC沉积物中的大气产生的（？归纳？）Be-10降临的记录，将这两个记录与每个记录的绝对约会无关，将这两个记录与每个记录的绝对约会相关联。格陵兰冰块的BE-10通量的十年分辨率记录已经存在。在这里，我们建议在NAVC的Varved沉积物中进行相应的BE-10测量到i）确定这些沉积物中的BE-10浓度是否记录BE-10的变化，ii）如果是），则会生成BE的记录-10辐射通量与现有的冰核记录相当，因此两者可以相关。