Collaborative Research: Borehole Logging to Classify Volcanic Signatures in Antarctic Ice

第一部分：非技术性的科学所能提供的最有趣的历史记录之一就包含在南极洲的冰中。数十万年来，雪一层一层地沉淀在冰盖上，变得致密，变成了额外的冰。空气或雪中的任何灰尘或其他杂质也会沉淀下来，因此每次降雪都会留下沉积时或接近沉积时存在的大气的快照记录。火山爆发的详细年表可以从火山灰和其他火山产物沉积的冰层中获得。通常情况下，分析火山层需要从冰盖中物理提取岩心;然而，岩心年表具有不连续性，并且难以获得，耗时且昂贵。钻孔测井是一种测量方法，其中一个降低仪器到一个钻孔的冰，无论核心是否已收回。迄今为止，这项技术仅用于测量光学系统，以识别火山灰和其他杂质层。在该计划中，将开发一种测量冰的导电性的剖面技术。一个射频发射器下降到钻孔将创建一个返回信号，根据当地的电导率，这取决于溶解离子的浓度变化。例如，溶解的硫酸盐是火山活动的重要标志，可能与沉积的火山灰不一致。其他溶解的离子，如氯化物，可以指示其他过程。预计这一钻孔剖面仪将能够帮助快速识别具有潜在全球影响的火山爆发，通过其频率依赖性区分不同的溶解离子，并协助建立不同冰芯和钻孔之间的年表。极地冰盖的钻孔测井是地球科学家识别和确定年代的最重要方法之一火山爆发然而，目前的技术只能显示火山喷发产生的火山灰的存在和深度。为了提取更详细的信息，必须获得冰芯，并在实验室中使用电导率或介电测量来费力地测量每个部分，以确定溶解的硫酸盐的存在或不存在及其相对于相应灰烬的位置。该计划将研究和演示一种与钻孔测井兼容的射频介电传感器，用于检测和测量冰中溶解的主要离子化学物质的峰值，特别是在对应于火山产生的硫酸盐的间隔中。硫酸盐层是火山产物的主要标志之一。然而，其他离子，如氯化物，钙等也常见于冰中，本项目的介电测井技术也将测量这些离子。预期某些离子集合将通过它们的频率依赖性来区分。这项技术可以指导其他研究人员，谁是使用传统的核心扫描和采样方法，特别感兴趣的区域在相应的core.We计划构建一个基于环的电极系统和测试该系统上的各种人工冰钻孔和冰芯。该装置不包括压力容器或其他钻孔测井仪填料。我们将测试应用电信号的不同方法，包括短脉冲和周期波。我们将进一步利用低噪声电路和滤波器的差分测量，以实现最大的灵敏度。我们将提取的信号与已知的硫酸盐和其他离子的摩尔浓度和测量的ECM记录相关联。我们将使用储存在海湾的真实的冰芯进行缩小规模的实验？在加州大学伯克利分校的实验室。 这将允许在具有天然杂质和多晶结构的冰中测试不同的设计。这个小集合包括来自南极洲和格陵兰岛不同地点的岩心，以及长达一百万年的各种年龄。

Part I: NontechnicalOne of the most interesting historical records that science can provide is contained in the ice of Antarctica. Layer by layer over hundreds of thousands of years, snow has precipitated on the ice sheet, become compacted, and turned into additional ice. Any dust or other impurities in the air or snow have been precipitated as well and thus each snowfall leaves a snapshot record of the atmosphere that existed at or near the time of deposition. A detailed chronology of volcanic eruptions can be obtained from the ice layers where ash and other volcanic products were deposited. Normally, the analysis of volcanic layers requires the physical extraction of a core from the ice sheet; however, chronologies from cores have discontinuities and are difficult, time-consuming, and expensive to obtain. Borehole logging is a measurement method where one lowers instrumentation into a drilled hole in the ice, whether or not core has been retrieved. To date, this technology has only been used to measure optical systems to identify volcanic ash and other impurity layers. In this program, a profiling technology will be developed that measures the conductivity of the ice. A radio-frequency emitter lowered into the borehole will create a return signal that changes depending on the local conductivity, which depends on the concentration of dissolved ions. For example, dissolved sulfates are a critical marker of volcanic activity that may not be coincident with deposited ash. Other dissolved ions, such as chloride, can be indicative of other processes. It is expected that this borehole profiling instrument will be able to help rapidly identify volcanic eruptions that had potentially global impact, distinguish between different dissolved ions via their frequency dependencies, and assist in establishing chronologies between different ice cores and boreholes.Part II: Technical DescriptionBorehole logging of the polar ice sheets is one of the most important methods that earth scientists have to identify and date volcanic eruptions. However, current technology only indicates the presence and depth of ash from an eruption. In order to extract more detailed information, one must obtain an ice core, and laboriously measure each section in the laboratory using electrical conductivity or dielectric measurements to determine the presence or absence of dissolved sulfate and its location relative to the corresponding ash, if any. This program will investigate and demonstrate a borehole logging-compatible radio-frequency dielectric sensor to detect and measure spikes in dissolved major ions chemistry in ice, particularly in intervals corresponding to volcanically produced sulfates. The sulfate layers are one of the primary signatures of volcanic products. However, other ions, such as chlorides, calcium, and others are also commonly seen in ice, and the dielectric logging technology of this program would also measure these. It is expected that certain sets of ions will be distinguishable by their frequency dependencies. This technique could guide other investigators, who are using conventional core scanning and sampling methods, to regions of special interest in corresponding core.We plan to construct a ring-based electrode system and test this system on a variety of artificial ice boreholes and ice cores. This unit will not include a pressure vessel or other borehole logger packing. We will test different means of applying electrical signals including short pulses and periodic waves. We will further utilize differential measurements with low noise circuits and filters to achieve maximum sensitivity. We will correlate the signals extracted with known molarities of sulfates and other ions and measured ECM records. We will perform scaled-down experiments using real ice cores stored in Bay?s lab at UC Berkeley. This will permit testing of different designs in ice with natural impurities and polycrystalline structure. This small collection includes cores from a variety of locations in Antarctica and Greenland, and a variety of ages as old as a million years.