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