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.

关于过去气候如何以及为什么过去发生变化的知识对于理解气候系统的敏感性以及对未来气候变化的潜力很重要。 有许多自然过程与气候和相关的海平面变化有关。随着冰片的生长，大陆冰川造成海平面，并在冰盖下降时提高海平面。从约50,000英里的海洋山脊上的海底火山中释放挥发物，尤其是二氧化碳（CO2），也被认为在调节气候中起着作用。海平面变化和挥发性释放是通过在海底和地面下地幔下面的压力变化来关联的。假设降低压力（通过海平面下降）会触发地幔融化和熔岩喷发增加到海底，从而导致岩浆二氧化碳的脱气，从而可以提高大气的二氧化碳含量并引起全球变暖。加热反过来导致冰川冰融化增加，从而对该过程产生了负面的反馈。 最近在太平洋太平洋 - 北极山脊上发表的作品表明，最近的冰川终止的特征是该位置的异常中山山脊火山症。但是，尚不清楚这只是巧合还是全球事件。这项研究旨在解决这个问题。为此，将检查现有收藏中的11个沉积物核心。根据中海脊轴向接近，水深和核心长度选择核心。这些特征对于记录山脊火山喷发的火山辐射所必需，这表明有效的岩浆作用。该研究涉及沉积物的密集地球化学和微观研究，使用氧同位素来确定核心地层和相干性，以及对火山灰含量的定量估计。如果成功，这项工作可能会对我们对气候变化和气候变化速度的理解产生影响。更广泛的影响还包括康涅狄格大学的本科生和研究生的培训。这项研究以对单个地点的初步研究为基础，在该研究中，大陆冰川的打蜡与中山山脊岩浆的发生率增加，然后是快速冰川熔化之间的关系。这项研究通过将观察结果扩展到三个主要海洋山脊扩散中心的多个位置：中大西洋山脊，东太平洋上升和中部印度山脊，来测试研究人员的小说和有争议的假设。可以通过NSF支持的海底样品存储库进行一组沉积物核心。这些核心具有阐明研究问题所需的基本标准：一个与中山山脊相近的位置，该山脊足够接近，该山脊的火山灰和射流可能是沉积物的组成部分，因此核心跨越了多个大陆冰川周期和水深。该项目的目标是确定在太平洋南极山脊上发现的结果是否代表了全球中山山脊的冰川终止状况。 核心的沉积物将被处理以分离有孔虫，该孔将用于氧同位素，以确定其地层和高分辨率的年龄。还将检查沉积物是否有灰烬，灰层和其他火山喷射的证据；火山材料的总量；以及火山粒子的形态和晶粒尺寸。将进行沉积物的地球化学分析，以寻找玄武岩颗粒的指标，通常从样品中的钛的重量百分比可以看出。这些数据将与大陆冰川时期的已知时期进行比较，以查看冰川的增加与下降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的法定任务，并被认为是值得通过基金会的知识分子和更广泛影响的评估来通过评估来获得支持的。