Snow depth, sea ice thickness and interface temperatures derived from measurements of SIMBA buoy 2020T77

The Snow and Ice Mass Balance Array (SIMBA) is a thermistor string type IMB (Jackson et al., 2013) which measures the environmental temperature SIMBA-ET and a temperature change around the thermistors after a weak heating is applied to each sensor (SIMBA-HT). SIMBA 2020T77 (a.k.a. PRIC_1005) is an autonomous instrument that was installed on drifting sea ice in the Arctic Ocean (Polarstern PS122 (MOSAiC) in 2019/20) as part of the project PRIC. Its thermistor chain is 5 m long, and equipped with 241 thermistors (Maxim Integrated DS28EA00) at a spacing of 2 cm. Based on a manual classification method, the SIMBA-ET and SIMBA-HT were processed to obtain snow depth and ice thickness (smoothed with a 3-day running mean), as well as the thermistor number, the vertical position Z relative to the snow-ice interface and the measured SIMBA-ET at each detected interface (atmosphere-snow, snow-ice and ice-ocean) for the period between 2020-04-04T14:30:17 and 2020-06-05T14:30:16. To do this, we combined two derivatives of measured temperatures (the ET vertical gradient and HT rise ratio) to reduce the detection uncertainty of all interfaces considered. The snow or ice surface, consequentially the snow depth, is determined by the ET vertical gradient. Potential formation of snow ice is not explicitly considered in this data set, but may occur as depicted by vertical changes of the snow-ice interface position. The ice-ocean interface is usually determined using the HT rise ratio and serves as the lower limit for ice thickness. Overall, the accumulated error is 2 to 4 times the sensor spacing for both the snow depth and ice thickness. For interface temperatures, individual sensors in the chain measure with a temperature resolution of 0.0625°C, with the overall accuracy landing in the range of ± 2°C (Jackson et al., 2013). After the snow cover has melted, negative values for snow depth may indicate the onset of ice surface melt.

雪冰质量平衡阵列（Snow and Ice Mass Balance Array, SIMBA）是一款热敏电阻串式冰质量平衡测量系统（IMB，Jackson等，2013），可同时测量环境温度SIMBA-ET，以及为每个传感器施加弱加热后热敏电阻周边的温度变化（SIMBA-HT）。SIMBA 2020T77（又名PRIC_1005）是一款自主观测仪器，于2019/2020年作为PRIC项目的组成部分，安装于北冰洋漂流海冰之上，搭载于德国极星号（Polarstern）PS122航次（MOSAiC科考计划）。该仪器的热敏电阻链总长5米，配备241个热敏电阻（美信集成Maxim Integrated DS28EA00），传感器间距为2厘米。研究人员基于人工分类方法，对SIMBA-ET与SIMBA-HT数据开展处理，以获取经3天滑动平均平滑后的雪深与冰厚数据；同时提取2020年4月4日14:30:17至2020年6月5日14:30:16期间，各探测界面（大气-积雪界面、积雪-海冰界面及海冰-海洋界面）对应的热敏电阻编号、相对于雪冰界面的垂直位置Z，以及实测SIMBA-ET温度值。为降低所有目标界面的探测不确定性，研究人员结合了实测温度的两个导数项——ET垂直梯度与HT上升比率，以此开展分析。积雪或冰面的位置（进而可推算雪深）由ET垂直梯度确定。本数据集未明确纳入雪冰的潜在形成过程，但可通过雪冰界面位置的垂直变化对其进行间接推断。海冰-海洋界面通常通过HT上升比率确定，可作为冰厚计算的下限值。总体而言，雪深与冰厚的累积误差为传感器间距的2至4倍。界面温度的测量中，该链状传感器的温度分辨率为0.0625℃，整体测量精度范围为±2℃（Jackson等，2013）。当积雪覆盖完全消融后，雪深的负值可作为冰面开始融化的指示信号。