EAGER: Anomalous submarine volcanism during glacial terminations: Exploring archives from the global mid-ocean ridge system

渴望：冰川终止期间的异常海底火山活动：探索全球大洋中脊系统的档案

• 批准号: 1840886
• 负责人: David Lund
• 金额: $ 4.99万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1840886&HistoricalAwards=false
• 关键词: EAGER; Anomalous; submarine; volcanism; during

Knowledge about how and why climate has changed in the past is important for understanding the sensitivity of the climate system and the potential for future climate change. There are many natural processes that are linked to climate and associated sea level changes. Continental glaciation draws down sea levels as ice sheets grow, and raises sea levels when ice sheets recede. The release of volatiles, especially carbon dioxide (CO2), from submarine volcanoes along the ~50,000 miles of mid-ocean ridges is also thought to play a role in modulating climate. Sea level changes and volatile release are linked through changes in pressure on the sea floor and underlying Earth's mantle. It is hypothesized that a reduction in pressure (through a drop in sea level) can trigger increased mantle melting and eruption of lava onto the seafloor, and consequent degassing of magmatic CO2 that can raise the CO2 content of the atmosphere and cause global warming. Warming in turn results in increased glacial ice melt, which provides a negative feedback to the process. Recently published work from the Pacific-Antarctic Ridge in the Southeast Pacific suggests that a recent glacial termination was characterized by anomalous mid-ocean ridge volcanism at that location. However, it is not clear if this is simply a coincidence or a global event. This research seeks to address this question. To do this, eleven sediment cores from existing collections will be examined. Cores were selected on the basis of mid-ocean ridge axial proximity, water depth, and core length. These characteristics are necessary for recording volcanic fallout from ridge volcanic eruptions that would indicate active magmatism. The research involves, intensive geochemical and microscopic study of the sediments, the use of oxygen isotopes to determine core stratigraphy and coherence, and quantitative estimates of volcanic ash content. If successful, the work could have implications for our understanding of climate and rates of climate change. Broader impacts also include the training of undergraduate and graduate students at the University of Connecticut. This research builds on a preliminary study of a single site in which a relationship appeared to exist between the waxing of continental glaciation and the increased incidence of mid-ocean ridge magmatism followed by rapid glacial melting. This research tests the researcher's novel and controversial hypothesis by expanding the observations to multiple locations on three major mid-ocean ridge spreading centers: the Mid Atlantic Ridge, the East Pacific Rise, and the Central Indian Ridge. A set of sediment cores are available for study through NSF-supported seafloor sample repositories. These cores have essential criteria needed to shed light on the research question: a location that is close enough to a mid-ocean ridge that volcanic ash and ejecta from eruptions therein are likely to be components of the sediment, length such that cores span multiple continental glacial cycles, and water depth. Goals of the project are to determine whether the results found on the Pacific Antarctic Ridge are representative of conditions of glacial terminations at mid-ocean ridges worldwide. Sediments from the cores will be processed to separate foraminifera that will be analyzed for oxygen isotopes to determine their stratigraphy and ages at high resolution. Sediments will also be examined for evidence of ash, ash layers, and other volcanic ejecta; the total amount of volcanic material; and volcanic particle morphology and grain size. Geochemical analyses on the sediments will take place to look for indicators of basaltic particles, usually evident from the weight percent of titanium in the samples. These data will be compared to the known timing of periods of continental glaciation to see if there is a correlation between the increase and decline of glaciation and corresponding seafloor magmatic activity.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.

了解过去气候如何以及为何发生变化对于了解气候系统的敏感性和未来气候变化的潜力非常重要。 有许多自然过程与气候和相关的海平面变化有关。大陆冰川作用随着冰盖的增长而降低海平面，并随着冰盖的消退而升高海平面。人们认为，沿着约 50,000 英里的洋中脊的海底火山释放的挥发物，尤其是二氧化碳 (CO2)，在调节气候方面也发挥着作用。海平面变化和挥发物释放通过海底和地幔下方压力的变化联系在一起。据推测，压力降低（通过海平面下降）会引发地幔融化加剧和熔岩喷发到海底，以及随之而来的岩浆二氧化碳脱气，从而提高大气中二氧化碳含量并导致全球变暖。变暖反过来会导致冰川融化增加，从而对该过程产生负反馈。 最近发表的来自东南太平洋太平洋-南极海脊的研究表明，最近的冰川终止的特点是该地点异常的洋中脊火山活动。然而，尚不清楚这只是巧合还是全球性事件。本研究旨在解决这个问题。为此，将对现有收藏中的十一个沉积物岩心进行检查。根据洋中脊轴向接近度、水深和岩心长度选择岩心。这些特征对于记录山脊火山喷发的火山沉降物是必要的，这表明活跃的岩浆活动。该研究涉及对沉积物进行深入的地球化学和微观研究，利用氧同位素确定岩心地层和相干性，以及定量估计火山灰含量。如果成功，这项工作可能会对我们对气候和气候变化速率的理解产生影响。更广泛的影响还包括康涅狄格大学本科生和研究生的培训。这项研究建立在对一个地点的初步研究的基础上，该地点的大陆冰川消融与大洋中脊岩浆活动发生率增加以及随后的冰川快速融化之间似乎存在某种关系。这项研究通过将观测范围扩大到三个主要洋中脊扩张中心的多个地点：大西洋中脊、东太平洋海隆和中印度洋脊，测试了研究人员新颖且有争议的假设。一组沉积岩芯可通过 NSF 支持的海底样本库进行研究。这些岩心具有阐明研究问题所需的基本标准：距离大洋中脊足够近的位置，其中火山灰和喷发物可能是沉积物的组成部分，长度使得岩心跨越多个大陆冰川循环和水深。该项目的目标是确定在太平洋南极海脊上发现的结果是否能够代表全球大洋中脊冰川终止的情况。 来自岩心的沉积物将被处理以分离出有孔虫，并对其进行氧同位素分析，以确定其地层和高分辨率的年龄。还将检查沉积物中是否存在火山灰、火山灰层和其他火山喷出物的证据；火山物质的总量；以及火山颗粒形态和粒度。对沉积物进行地球化学分析，以寻找玄武岩颗粒的指标，通常可以从样品中钛的重量百分比看出。这些数据将与已知的大陆冰川期时间进行比较，以了解冰川作用的增加和减少与相应的海底岩浆活动之间是否存在相关性。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准。