Collaborative Research: Tephrochronology of a South Pole Ice Core

南极冰芯提供了无与伦比的地球记录？美国的气候可以追溯到近一百万年甚至更久以前。埋在冰川中的火山灰层可以用来建立精确的冰芯年代学。为了使用可见或超细火山灰层作为时间地层标志，必须建立独特的地球化学指纹，这是我们研究的基础。该奖项将调查2015/16年野外季节在南极完成的1751米冰芯中的火山记录。冰芯所处的位置非常理想，可以连接南极东部和西部现有的、已建立的火山记录，从而连接和整合这些记录，从而可以直接比较冰芯的气候记录，并将研究重点放在南极西部最广泛和最重要的火山爆发上。研究人员还将研究从年代久远的大型热带火山喷发中提取的热菌，这些火山喷发可能对气候产生了影响。最近在识别和分析这些喷发类型的非常细的火山灰颗粒方面取得的成功，使我们有可能能够确定其中的一些喷发，这将使与这些层相关的硫酸盐峰得到积极的识别和确定年代。基于保存的硫酸盐的早期南极冰芯形成的火山强迫时间序列对于测试气候模型至关重要，但如果没有tephra分析，这些层的起源仍然不确定。对南极冰芯中温度层的研究有许多重要的具体目标，其中一些对南极冰芯的基本科学目标具有实际应用价值，而另一些则代表着独立的科学贡献。这些包括：(1)在地核中提供独立确定的时间间隔，特别是在最深的冰层中；(2)定量地将整个南极洲的温度记录联系起来，以便在大陆的这些不同地区之间进行直接和可靠的气候比较；(3)提供大型局部喷发的信息，从而直接估计南极火山的喷发规模和扩散模式，其中一些火山可能会再次喷发。工作的初始阶段将通过使用几种方法确定冰芯中含硅酸盐的层位来进行。一旦发现，硅酸盐颗粒将被成像，以便颗粒的形态特征可以用来识别火山起源。鉴定为麻黄的颗粒将使用电子探针和激光烧蚀ICP-MS进行化学分析。产生强大化学指纹的样本将在统计上与已知的火山爆发相关联，这将用于解决上述目标。该项目的更广泛影响落在下一代研究人员的教育，推广和国际合作领域。这些活动将继续推动整合南极火山记录并将其与全球火山记录更广泛地联系起来的工作取得进展。

Dunbar/1543454Antarctic ice cores offer unparalleled records of earth?s climate back to almost one million years and perhaps beyond. Layers of volcanic ash (tephra) embedded in glacial ice can be used to establish an accurate ice core chronology. In order to use a visible or ultrafine volcanic ash layer as a time-stratigraphic marker, a unique geochemical fingerprint must be established, and this forms the basis of our research. This award will investigate the volcanic record in the 1751 m ice core that was completed at the South Pole during the 2015/16 field season. The core is in an ideal location to link the existing, established, volcanic records in East and West Antarctica, and therefore to connect and integrate those records, allowing the climate records of ice cores to be directly compared, as well as to focus research on the most widespread and significant volcanic eruptions from West Antarctica. Tephra derived from well-dated, large, tropical volcanic eruptions that may have had an impact on climate will also be studied. Recent success in identifying and analyzing very fine ash particles from these types of eruptions makes it likely that we will be able to pinpoint some of these eruptions, which will allow the sulfate peaks associated with these layers to be positively identified and dated. Volcanic forcing time series developed from earlier South Pole ice cores based on preserved sulfate were crucial for testing climate models, but without tephra analysis, the origin of these layers remains uncertain. Work on the tephra layers in the South Pole ice core has a number of significant specific objectives, some with practical applications to the basic science goals of Antarctic ice coring, and others that represent independent scientific contributions in their own right. These include: (1) providing independently dated time-intervals in the core, particularly for the deepest ice, (2) quantitatively linking tephra records across Antarctica with the goal of allowing direct and robust climate comparisons between these different parts of the continent, (3) providing information for large local eruptions, that will lead to direct estimates of eruption magnitude and dispersal patterns of Antarctic volcanoes, several of which will likely erupt again. The initial stages of the work will be carried out by identifying silicate-bearing horizons in the ice core, using several methods. Once found, silicate particles will be imaged so that morphological characteristics of the particles can be used to identify volcanic origin. Particles identified as tephra will then be chemically analyzed using electron microprobe and laser ablation ICP-MS. Samples that yield a robust chemical fingerprint will be statistically correlated to known eruptions, and this will be used to address the goals described above. Broader impacts of this project fall into the areas of education of future generation of researchers, outreach and international cooperation. These activities will continue to promote forward progress in integrating the Antarctic tephra record and more broadly tying it to the global volcanic record.