DC Conductivity of sea-ice measured during the SIPEX II voyage of the Aurora Australis, 2012

DC Electrical:

In order to relate the fluid permeability to the electrical properties of sea ice, we also took measurements of the vertical component of the DC electrical conductivity tensor of sea ice. Cores extending to the bottom of an ice floe were taken and laid out holder. With the exception of sites 7 and 8 where we encountered a slush layer below the hard ice and could not core down to the ocean. The core bottom was determined at sites 7 and 8 to be the ice slush interface. Immediately upon extraction, holes that fit our thermistor probes were drilled every ten centimetres and a temperature profile was taken. Subsequently, slightly larger holes were drilled which fit our electrical probes (stainless steel nails). An AEMC Earth Resistivity Meter was then used to measure the resistance over 10 cm sections of the core (usually offset by 5 cm so that the measured temperature was in the centre of the section where electrical resistance was measured).

The cores used in resistance measurements were taken very close to where the crystallographic cores were taken. In almost all cases the cores extracted for electrical measurements were also used for crystallographic analysis, so that there was an exact match of electrical properties with crystal structure. In such cases the DC electrical cores were then moved to a -20 degree C cold room for further processing immediately after measurements in the field.

A thin vertical section, approximately 3mm thick, was taken from each of the cores stored for analysis. These sections were placed between a pair of cross polarized plates and photographed. Each photo was labelled with the core and date it was taken, and was photographed with a meter stick alongside for scale.

After the thin sections were photographed, the remaining samples were melted to measure salinity. Some of the melted sea ice was saved for later O18 analysis to distinguish samples containing snow ice from those containing marine granular ice. The temperature and salinities we are then used to calculate brine volume fractions along the 10 cm sections of the core.

The DC conductivity data collected can be found in the Electrical tab of the Master_Core_List.xls Excel file. The raw data can be found in the scans of our field note books located in the folder named notebooks. In the spread sheet the measured resistances of the 10 cm sections, temperatures, salinities and corresponding brine volume fractions are listed per core.

For each core the supporting crystallography core number can be found in the crystallography column of the spread sheet. The photos of the crystallography cores can be found in the crystallography folder, separated into subfolders labelled with the site and core number, Each photo also contains a tag indicating the core number , site taken , date, and what depth range this covers. Tags may not contain a depth range for cores less than 1 meter. Please see the meter stick in each photo for scale.

直流电学测量：

为建立流体渗透率与海冰电学特性之间的关联，我们同时开展了海冰直流电导率张量（DC electrical conductivity tensor）垂直分量的测量工作。采集了延伸至浮冰（ice floe）底部的冰芯，并将其安置于样品支架中。但第7、8站位除外：该处坚硬冰层下方存在雪泥层，我们未能将冰芯钻至海洋层面。第7、8站位的冰芯底部被确定为冰-雪泥界面。冰芯一经取出，便每隔10厘米钻设适配热敏电阻探头（thermistor probes）的孔洞，随后获取温度剖面数据。随后，钻设尺寸稍大的孔洞以安装电学探头（不锈钢钉）。随后使用AEMC接地电阻率仪（AEMC Earth Resistivity Meter）测量冰芯每10厘米段的电阻值（测量位置通常偏移5厘米，以使测得的温度处于该电阻测量段的中心位置）。

用于电阻测量的冰芯采集位置与晶体学冰芯（crystallographic cores）的采集位置极为接近。几乎所有情况下，用于电学测量的冰芯同时也被用于晶体结构分析，从而实现电学特性与晶体结构的精准匹配。在此类情况下，野外测量完成后，直流电学冰芯会立即被转移至-20℃的冷室（cold room）中进行后续处理。

从每一块留存待分析的冰芯上切取厚度约3毫米的垂直薄片。将这些薄片置于一对正交偏振片（cross polarized plates）之间并进行拍照。每张照片均标注有冰芯编号与拍摄日期，并在旁侧放置标尺（meter stick）以提供尺寸参照。

薄片拍照完成后，将剩余样品融化以测量盐度（salinity）。留存部分融化后的海冰样品用于后续的氧18同位素（O18）分析，以区分含雪冰（snow ice）的样品与含海洋粒状冰（marine granular ice）的样品。随后利用测得的温度与盐度数据，计算冰芯每10厘米段的盐水体积分数（brine volume fractions）。

本次采集的直流电导率数据可在Master_Core_List.xls Excel文件的Electrical标签页中获取。原始数据则存放在名为notebooks的文件夹内的野外记录簿扫描件中。在该电子表格中，按冰芯列出了每10厘米段的实测电阻值、温度、盐度及对应的盐水体积分数。

每块冰芯对应的配套晶体学冰芯编号可在电子表格的crystallography列中找到。晶体学冰芯的照片存放在crystallography文件夹中，该文件夹下按站位与冰芯编号划分了子文件夹。每张照片均带有标注，包含冰芯编号、采集站位、拍摄日期以及所覆盖的深度范围。对于长度不足1米的冰芯，标注中可能未包含深度范围。请参照每张照片中的标尺获取尺寸比例。