Mooring observation data in the Cape Darnley polynya, Antarctica, 2010-2011 (JARE-51)

We conducted mooring observations with acoustic Doppler current profilers (ADCPs) and conductivity-temperature (CT) recorders inside the Cape Darnley polynya throughout winter for the first time. Two moorings were deployed near the shore (a1: bottom depth 183 m) and the shelf edge (a2: bottom depth 270 m). Each mooring was equipped with an Ice Profiling Sonar (IPS: ASL Environmental Sciences, IPS4 420 kHz), an upward-looking acoustic Doppler current profiler (ADCP: RD Instruments Workhorse Sentinel 300 kHz), and conductivity-temperature recorders (CT-recorders: SeaBird SBE-37 MicroCAT) from the top. The ADCPs at a1 and a2 measured the volume backscatter strength (SV) in addition to the current velocity for 9 and 10 layers of bin, respectively, with the 8 m interval. The pre-deployment calibration demonstrated a temperature accuracy of 2 mK and a salinity accuracy of 4 X 10-3. ADCP and CT-recorder depths were calculated from the pressure by the IPS pressure sensor and the tilt measured by the ADCP with an assumption that the mooring line was straight. In this region, the iceberg tongue in the east creates a risk of an iceberg attack on the moorings. In fact, the mooring at a2 was attacked by an iceberg twice, which was recorded by the pressure sensor as rapid dives. Fortunately, both moorings survived for one year.

本研究首次在达恩利角冰间湖（Cape Darnley polynya）整个冬季期间，利用声学多普勒海流剖面仪（acoustic Doppler current profilers, ADCPs）与温盐（conductivity-temperature, CT）记录仪开展锚碇观测。本次共部署两套锚碇系统，分别位于近岸区域（a1：海底水深183 m）与陆架边缘（a2：海底水深270 m）。每套锚碇系统自顶部起依次搭载冰剖面声呐（Ice Profiling Sonar, IPS：ASL环境科学公司，IPS4 420 kHz）、向上观测型声学多普勒海流剖面仪（ADCP：RD Instruments Workhorse Sentinel 300 kHz）以及温盐记录仪（CT-recorders：SeaBird SBE-37 MicroCAT）。a1与a2处的ADCP除观测海流流速外，还分别以8米的采样间隔对9层与10层的体积后向散射强度（volume backscatter strength, SV）进行了测量。部署前的校准结果显示，其温度测量精度可达2毫开尔文（mK），盐度测量精度可达4×10⁻³。研究通过IPS压力传感器获取的压力数据，以及ADCP测得的倾斜角，并假设锚碇缆绳呈直线状态，计算得到ADCP与CT记录仪的实际部署深度。该区域东侧的冰舌存在对锚碇系统造成撞击的风险。事实上，a2处的锚碇系统曾两次遭遇冰山撞击，该事件被压力传感器以锚碇快速下沉的压力变化形式记录下来。所幸两套锚碇系统均完成了为期一年的观测任务。