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

非技术性的北美冰蚀年表（NAVC）是一个近6000年的年度沉积层序列，这些沉积层沉积在劳伦泰德冰盖边缘附近的冰川湖泊中，在最后一个冰河时代覆盖了北美的大部分地区。在这些沉积物沉积的时候，大约在12，500到18，000年前，气候正在变暖，劳伦泰德冰盖正在迅速缩小。组成NAVC的沉积物是每年解决的事件发生在退缩的冰缘，包括冰缘的位置和退缩速度，夏季冰盖融化产生的水通量，以及大冰川湖爆发洪水，定期发生的冰缘湖排水。 该提案的目标是了解这些事件与同时发生的气候变化的关系，并记录在格陵兰的冰芯记录中，这很重要，因为i）它将有助于了解大冰盖如何应对快速气候变暖，以及ii）因为这一时期是当前快速变暖和冰川和冰盖可能萎缩时期的潜在模拟。将NAVC与格陵兰气候记录进行比较的障碍在于，尽管这两种记录都有独立的日期，但这些日期的精确度是几百年，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沉积物和格陵兰冰芯中大气产生的BER 10的记录来解决这个问题。Be-10是一种天然存在的稀有铍同位素，由宇宙射线轰击高层大气产生，并以降水形式福尔斯落到地球上。由于地球磁场的变化，Be-10的产量随着时间的推移而变化，这些变化同时发生在地球上的任何地方。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，格陵兰冰芯和NAVC湖沉积物中的Be-10浓度应显示相同的变化模式。通过将这些更改相互对齐，我们可以将这两个记录放在一个公共的时间尺度上。因此，即使我们不知道格陵兰冰芯中记录的特定气候变化发生的确切时间，我们也会确切地知道当时NAVC沉积物中记录的冰缘事件发生了什么。我们预计，我们将能够匹配这两个记录与几十年的精度，这应该是足够精确的，以确定重要的气候变化和冰盖变化之间的关系。TechnicalThe North American Varve Chronology（NAVC）是一个5659年的序列，每年层积沉积物（？varves？）沉积在邻近北美东部正在消退的劳伦蒂德冰盖（LIS）的湖泊中。这是一个每年解决的冰边缘位置，融水和沉积物通量，和冰前湖溃决洪水之间的约。在12,500到18,000年前。该项目的目标是将这一纹藻年表与来自格陵兰冰芯的同期气候记录相关联。这一点很重要，因为这种相关性将揭示陆地冰缘事件与北大西洋气候变化之间的时间关系，这反过来又将揭示晚冰期冰盖-气候相互作用的未解决方面，包括，例如，i）LIS边缘的冰前湖溃决洪水对北大西洋气候的影响，ii）北大西洋气候对LIS东南缘表面消融和退缩的影响，以及iii）在这段时间内格陵兰持续寒冷的气候和显著的冰缘退缩之间的明显冲突。该小组建议通过比较大气产生的（？）流星？）格陵兰冰芯和NAVC沉积物中的Be-10沉降物。格陵兰冰芯Be-10通量的十年分辨率记录已经存在。在这里，我们建议进行相应的Be-10测量的NAVC的纹状沉积物中，以i）确定这些沉积物中的Be-10浓度是否记录在Be-10沉降物的变化，和ii）如果是这样，生成一个记录的Be-10沉降通量可比现有的冰芯记录，使两者可以相关。

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.