Collaborative Research: Tephrochronology of a South Pole Ice Core

邓巴/1543454南极冰芯提供了无与伦比的地球气候记录，可以追溯到近一百万年前甚至更久远。嵌入冰川冰中的火山灰（火山灰）层可用于建立准确的冰芯年代学。为了使用可见或超细火山灰层作为时间地层标记，必须建立独特的地球化学指纹，这构成了我们研究的基础。该奖项将调查 2015/16 野外季节期间在南极完成的 1751 米冰芯的火山记录。该冰芯位于连接东南极洲现有的、已确定的火山记录的理想位置，因此可以连接和整合这些记录，从而可以直接比较冰芯的气候记录，并集中研究西南极洲最广泛和最重要的火山喷发。 还将研究源自年代久远的大型热带火山喷发的火山灰，这些火山喷发可能对气候产生影响。 最近在识别和分析这些类型的喷发中非常细的火山灰颗粒方面取得的成功，使我们有可能能够精确定位其中一些喷发，这将使与这些层相关的硫酸盐峰能够被积极地识别和测定日期。基于保存的硫酸盐从早期南极冰芯发展而来的火山强迫时间序列对于测试气候模型至关重要，但如果没有火山灰分析，这些层的起源仍然不确定。对南极冰芯火山灰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础科学目标有实际应用，而另一些则本身代表了独立的科学贡献。其中包括：（1）提供核心的独立日期时间间隔，特别是最深的冰层，（2）定量连接整个南极洲的火山灰记录，目的是对大陆不同地区之间的气候进行直接和强有力的比较，（3）提供大规模局部喷发的信息，这将导致直接估计南极火山的喷发强度和扩散模式，其中一些火山可能会再次喷发。这项工作的初始阶段将通过使用多种方法识别冰芯中的硅酸盐层位来进行。 一旦发现，将对硅酸盐颗粒进行成像，以便利用颗粒的形态特征来识别火山起源。 然后，将使用电子微探针和激光烧蚀ICP-MS 对鉴定为火山灰的颗粒进行化学分析。 产生强大化学指纹的样本将与已知的喷发进行统计相关，这将用于实现上述目标。 该项目更广泛的影响涉及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灰记录并更广泛地将其与全球火山记录联系起来。

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.