Dome Fuji, Antarctica Core DF2 1-cm AC-ECM Data

Dome Fuji, Antarctica Ice Core DF2 1 cm AC-ECM Data at -20C, for depth range 975 - 2200m. The climatic record from the 2nd Dome Fuji (Antarctica) deep ice core was analyzed using AC-ECM (AC electrical conductivity measurements). AC-ECM is a method to detect the complex admittance between electrodes dragged on the ice surface with mm-scale resolution and uses 1V and 1MHz. Methods are as follows. After equilibrating for 1 day at the cold-roomtemperature at Dome F, all core sections, which were 93mm in diameter and about 1.5 m long, were cut parallel to their central axes. The cut surfaces were further finished with a microtome knife to make fresh, smooth surfaces. Immediately after a surface was cut and finished, two AC-ECM electrodes were dragged along the surface with a 1 MHz frequency, 1 V signal. The AC-ECM electrodes were automatically dragged along the ice with 2mm step using a moter module. Although the signal was sampled every 2mm, we provide only 10mm running averages of the data to remove noise. The AC-ECM system consists of two coaxial electrodes and an auto-balance bridge (HP model 4284A precision LCR meter). It measures the complex admittance Y= G+Bi, where G is the conductance and B is the susceptance, at the surface of ice using 1MHz to detect the high-frequency limit conductance of ice; here high-frequency limit means frequency well above the Debye dispersion only, and below the dispersions that exist above the microwave region. The electrodes were aligned perpendicular to the core axis and 15mm apart. The effective resolution of the electrodes approximately equaled the distance between the electrodes (15mm); based on a physical principle that the electrical field decreases inversely proportional to the distance from a given location to each electrode. Within this distance, about 65% of the lines of electrical force cross. In earlier studies, the AC loss factor (loss tangent) was given as a result of the AC-ECM. It was G/B, conductance divided by susceptance. The loss factor is proportional to the concentration of sulfuric acid and hydrogen ions. In this set of data, we provide our results as conductance G. In 2015, Fujita, Parrenin et al. (2015) volcanically synchronized two deep ice cores, Dome Fuji (DF) and EPICA Dome C (EDC), drilled at remote dome summits in Antarctica, to improve our understanding of their chronologies. For their study, AC-ECM data of the DF2 core were used from a limited depth range 975-2200m. Here, we open these data to the public. The data have two information of the depth. The first column is the depth of the DF2 core. The third column is the DF2 depths converted into equivalent depths of the DF core. The second column is the conductance (nS) between the electrodes. Note that, in this version of the data, no actions for noise cleaning were done. Except the averaging for every 10mm, data is still a kind of raw data.南极富士穹顶（Dome Fuji）DF2冰芯在-20℃下的1厘米AC-ECM数据，覆盖深度范围975~2200米。本研究采用交流电导率测量法（AC-ECM，AC electrical conductivity measurements），对第二座南极富士穹顶深冰芯的气候记录展开分析。AC-ECM是一种以毫米级分辨率检测拖拽于冰面的电极间复导纳的方法，测试信号参数为1V与1MHz。 实验流程如下：将直径93mm、长约1.5m的冰芯段在富士穹顶冷室温度下平衡1天后，沿其中心轴平行切割。切割面再用切片机刀具进一步修整，得到平整新鲜的冰面。在切割修整完成后，立即使用1MHz频率、1V的交流信号，将两个AC-ECM电极沿冰面拖拽。该电极系统通过电机模块以2mm步长自动沿冰面移动。尽管采样间隔为2mm，但为去除噪声，本次发布的数据仅保留10mm滑动平均值。 AC-ECM系统由两个同轴电极与自动平衡电桥（惠普HP 4284A型精密LCR测试仪）组成。该系统在冰面测量复导纳Y=G+Bi，其中G为电导，B为电纳，测试频率选用1MHz，以获取冰的高频极限电导；此处的高频极限指频率仅远高于德拜色散（Debye dispersion），且低于微波频段以上存在的色散。电极与冰芯轴垂直对齐，间距为15mm。根据电场强度与到电极的距离成反比的物理原理，电极的有效分辨率近似等于电极间距（15mm）；在此间距内，约65%的电力线会穿过测量区域。 在以往研究中，AC-ECM的结果会给出交流损耗因子（损耗正切），其值为G/B，即电导除以电纳。该损耗因子与硫酸及氢离子的浓度呈正比。本次数据集仅提供电导G的测量结果。 2015年，Fujita、Parrenin等人（2015）通过火山层同步法，对两座分别钻探于南极偏远穹顶之巅的深冰芯——富士穹顶（DF）与EPICA Dome C（EDC）——进行了定年优化，以深化对其年代序列的理解。该研究使用了DF2冰芯在有限深度范围975~2200m内的AC-ECM数据。本次我们将这批数据向公众开放。 本数据集包含两类深度信息：第一列为DF2冰芯的原始深度；第三列为转换为DF冰芯等效深度的深度值；第二列为电极间的电导（单位：纳西门子（nS））。需注意，本版数据未进行额外的噪声清洗操作，仅完成了每10mm的滑动平均处理，仍属于原始数据范畴。