CTD and LADCP measurements in the Vidal Channel during cruise 94 of the R/V Akademik Mstislav Keldysh in 2024
Description
A detailed CTD/LADCP survey in the Vidal Channel (Western Tropical Atlantic) was carried out during cruise 94 of the R/V “Akademik Mstislav Keldysh” in January, 2024. The main objective of this survey was to measure abyssal gravity currents of Antarctic Bottom Water and to estimate its transport to the Northwest Atlantic. The stations were located along the entire channel from 12°N to 17N. A total of 30 full water depth stations (down to the bottom) were performed in the Vidal Channel. The lowered system included the Conductivity, Temperature, and Depth (CTD) profiler Idronaut Ocean Seven 320 and Lowered Acoustic Current Doppler Profiler (LADCP) Teledyne RD Instruments WorkHorse Monitor 307.2 kHz with an external battery package. An additional AML3 LGR autonomous CTD probe with high accuracy sensors was used to validate the Idronaut CTD probe. 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 to 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 channel. Each station took approximately 4 hours (the descent and ascent rates of the CTD and LADCP profilers were approximately 1 m/s); the entire survey was performed from January 4 to January 14, 2024.