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

了解过去气候变化的方式和原因，对于了解气候系统的敏感性和未来气候变化的可能性非常重要。有许多自然过程与气候和相关的海平面变化有关。随着冰盖的扩大，大陆冰川作用降低了海平面，当冰盖消退时，大陆冰川作用又升高了海平面。海底火山沿着约50,000英里的大洋中脊释放挥发物，特别是二氧化碳(CO2)，也被认为在调节气候方面发挥了作用。海平面的变化和挥发性物质的释放通过海底和地幔下压力的变化联系在一起。据推测，压力的降低(通过海平面的下降)可能会引发地幔熔化增加，熔岩喷发到海底，从而导致岩浆二氧化碳的脱气，从而提高大气中的二氧化碳含量，导致全球变暖。变暖反过来会导致冰川融化增加，这对这一过程提供了负面反馈。最近在东南太平洋的太平洋-南极海脊发表的研究表明，最近的一次冰川终止是该地点异常的大洋中脊火山活动的特征。不过，目前尚不清楚这只是一个巧合，还是全球性事件。这项研究试图解决这个问题。为了做到这一点，将对现有收集的11个沉积物岩芯进行检查。岩芯的选择是基于大洋中脊的轴向距离、水深和岩心长度。这些特征对于记录来自山脊火山喷发的火山尘埃是必要的，这将表明岩浆活动活跃。这项研究涉及对沉积物进行深入的地球化学和微观研究，使用氧同位素来确定岩心地层学和连贯性，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。这项研究建立在对单一地点的初步研究基础上，在该地点，大陆冰川的融化似乎与大洋中脊岩浆活动的增加以及随后迅速的冰川融化之间存在关系。这项研究通过将观测范围扩大到三个主要的大洋中脊扩张中心：中大西洋海脊、东太平洋隆起和中印度洋海脊，来检验这位研究人员新颖而有争议的假设。一组沉积物岩心可通过国家科学基金会支持的海底样本库进行研究。这些岩芯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，火山灰和喷发出来的火山灰很可能是沉积物的组成部分，岩芯跨越多个大陆冰川周期的长度，以及水深。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代表世界各地大洋中脊冰川终止的条件。来自岩心的沉积物将被处理以分离有孔虫，这些有孔虫将被分析出氧同位素，以高分辨率确定其地层和年龄。还将检查沉积物中是否有火山灰、火山灰层和其他火山喷发的证据；火山物质的总量；以及火山颗粒的形态和粒度。将对沉积物进行地球化学分析，以寻找玄武岩颗粒的指示物，通常从样品中钛的重量百分比可以看出这一点。这些数据将与大陆冰川时期的已知时间进行比较，以确定冰川活动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。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.