CTD and LADCP measurements in the Romanche Fracture Zone during cruise 62 of the R/V Akademik Ioffe in August, 2022
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A detailed CTD/LADCP survey in the Romanche Fracture Zone was carried out during cruise 62 of the R/V Akademik Ioffe in August, 2022. The main idea of this survey was to measure abyssal currents of Antarctic Bottom Water and estimate its transport to the East Atlantic. The stations were located in the middle part of the fracture zone at the entrance to the Vema Deep (the deepest depression in the fracture zone). In total, 23 full water depth stations (down to 5865 m) were performed in three channels of the sill between two neighboring deep basins of the Romanche Fracture Zone. The rosette system General Oceanics GO1018 included Idronaut Ocean Seven 320 plus Conductivity-Temperature-Depth (CTD) probe and Lowered Acoustic Doppler Current Profiler (LADCP; 300 kHz Teledyne RD Instruments WorkHorse Monitor with an external battery package). The velocity profiler was set in the narrowband mode, which increases the profiling range in comparison with the broadband mode and allows more reliable processing of the raw data. We set 30 vertical bins of 8 m each with 1.76 m blank distance immediately below the transducer. The LADCP compass was calibrated before the cruise in the down looking mode according the standard procedure. The raw data were processed using the LDEO Software version IX_14. We stopped the casts at a distance of 5 m above the bottom using the altimeter (model Valeport VA500) and pinger of the Benthos Co. The combined use of a pinger and an altimeter allowed us to safely approach the bottom even in conditions of rough bottom topography. A 6000-m sea cable allowed measurements at any point of the sill. The main section across the fracture zone included eight stations (62025-62032) at a distance of 2.5-4.3 km from each other. Two background stations (62023 and 62045) were occupied at the adjacent Vavilov and Vema deeps. Date and time are indicated for the moment when the CTD was near the bottom; the ocean depth was determined based on the CTD pressure and altimeter records. Each station took approximately 4 hours (the descent and ascent rates of the CTD and LADCP profilers were 1 m/s); the entire survey took 4.5 days.
2022年8月，“约夫院士”号（R/V Akademik Ioffe）科考船第62航次在罗曼奇断裂带（Romanche Fracture Zone）开展了详细的温盐深（Conductivity-Temperature-Depth, CTD）与下投式声学多普勒流速剖面仪（Lowered Acoustic Doppler Current Profiler, LADCP）综合调查。本次调查的核心目标为测量南极底层水（Antarctic Bottom Water）的深渊流系，并估算其向东大西洋的输运量。调查站位布设至断裂带中部、维玛海渊（Vema Deep，该断裂带最深凹陷）的入口区域。本次调查共在罗曼奇断裂带两个相邻深海盆地间的海槛三条水道中布设23个全水深站位，最大探测深度达5865米。本次调查采用General Oceanics GO1018型Rosette采水系统，该系统搭载Idronaut Ocean Seven 320 plus型温盐深探头，以及型号为300 kHz Teledyne RD Instruments WorkHorse Monitor的下投式声学多普勒流速剖面仪，并搭配外置电池组。该流速剖面仪工作于窄带模式，相较宽带模式可提升剖面探测范围，并能对原始数据进行更可靠的处理。系统设置30个垂直测仓，每个测仓间距8米，换能器下方初始盲区距离为1.76米。航次前，已按照标准流程对LADCP罗盘进行朝下模式校准。原始数据采用LDEO软件IX_14版本进行处理。本次调查采用Valeport VA500型高度计与Benthos公司的脉冲声呐，在距海底5米处终止CTD采水作业；高度计与脉冲声呐的联合使用，即便在复杂海底地形条件下，也可保障安全近底作业。配套的6000米深海缆绳可实现海槛任意点位的测量作业。横跨断裂带的主断面共布设8个站位（编号62025-62032），站位间距为2.5~4.3千米。另在相邻的瓦维洛夫海渊与维玛海渊布设2个背景站位（编号62023与62045）。数据的日期与时间标记为CTD抵达近底时刻；海洋水深通过CTD压力与高度计记录联合确定。单个站位作业时长约4小时（CTD与LADCP剖面仪的下潜、上浮速率均为1米/秒）；整个调查航次总耗时4.5天。
