Abyssal oceanographic measurements in the Western Gap (Northeast Atlantic) in October 2021

A detailed oceanographic survey in the Western Gap of the Azores-Gibraltar Fracture Zone in the Northeast Atlantic was carried out during cruise 59 of the R/V “Akademik Ioffe” in October, 2021. The main objective of this survey was to measure abyssal currents of Antarctic Bottom Water and estimate its northward transport to the Iberian Basin. The survey included measurements of the themohaline, kinematic structures of the abyssal flow, as well as hydrochemical parameters of bottom waters. A total of 11 oceanographic stations with the SBE-32SC carousel water sampler were performed. The sampler was equipped with an SBE 19plus V2 SeaCAT probe and a Teledyne RD Instruments Workhorse Sentinel 300 kHz Lowered Acoustic Doppler Current Profiler. Water sampling to determine dissolved oxygen and concentrations of silicates was performed using Niskin bottles (volume 2.5 L; General Oceanics). To study near-bottom water layer properties, all water samples were taken in the depth range from the bottom up to 4000 m at 6–8 levels. The number of samples and depth of sampling were chosen based on CTD data. The CTD and LADCP data processing was performed using the SBE Data Processing 7.26.2 package and the LDEO Software version IX.14, respectively. Determination of dissolved oxygen concentration in seawater samples was performed according to the classical Winkler iodometric titration method using a digital burette Akvilon ATP-1d, the standard error of method is 0.02 mL/L (0.85 µmol/kg). Determination of concentrations of silicates was based on the photometric method using a KFK-3KM spectrophotometer.2021年10月，“约费院士”号（R/V "Akademik Ioffe"）科考船第59航次，在东北大西洋亚速尔-直布罗陀断裂带（Azores-Gibraltar Fracture Zone）西隙区域开展了详细的海洋学调查。本次调查的核心目标为实测南极底层水（Antarctic Bottom Water）的深渊海流，并估算其向北向伊比利亚盆地（Iberian Basin）的输运通量。本次调查涵盖了深渊流的温盐结构、运动学特征，以及底层海水的水化学参数测量。本次调查共布设11个海洋学站位，采用SBE-32SC型旋转式采水器（SBE-32SC carousel water sampler）完成水样采集。该采水系统搭载有SBE 19plus V2 SeaCAT型探头，以及Teledyne RD Instruments公司生产的Workhorse Sentinel 300 kHz下放式声学多普勒流速剖面仪（Lowered Acoustic Doppler Current Profiler, LADCP）。用于测定溶解氧与硅酸盐浓度的水样，采用General Oceanics公司生产的容积为2.5 L的Niskin采水瓶采集。为探究近底层水体的理化特性，所有水样均在从海底至4000 m的深度范围内，按6~8个分层进行采集。采样层数与各层采样深度均依据温盐深仪（Conductivity-Temperature-Depth, CTD）采集的数据确定。CTD与LADCP数据分别采用SBE Data Processing 7.26.2软件包与LDEO Software IX.14版本进行后期处理。海水样品的溶解氧浓度测定采用经典的温克勒碘量滴定法，使用Akvilon ATP-1d型数字滴定管完成，该方法的标准误差为0.02 mL/L（0.85 µmol/kg）。硅酸盐浓度的测定基于光度分析法，使用KFK-3KM型分光光度计完成。