Multibeam bathymetry processed data (EM 120 echosounder & Kongsberg EM 122 dataset compilation) of RV MARIA S. MERIAN during cruise MSM11/2, MSM82/2 & MSM87, North Atlantic Ocean

The bulk of multibeam bathymetric data were acquired during RV Maria S. Merian cruises MSM11/2 (Bickert et al., 2009), MSM82/2 (Krastel et al., 2019a) and MSM87 (Krastel et al., 2019b) with hull-mounted Kongsberg Simrad systems EM120 (MSM11/2) and EM122 (MSM82/2 and MSM87). The nominal sonar frequency is 12 kHz. The angular coverage is up to 150°, and each angular beam accuracy was 2° by 2°. Kongsberg Seapath system provides the combined motion, position and time data, which are transmitted to the Processing Unit (PU) of the multibeam echosounder to achieve real-time motion compensation in pitch, roll and yaw. All raw data were processed with MB-System software (Caress and Chayes, 2017: https://www.mbari.org/products/research-software/mb-system/). Sound velocities were measured with a Conductivity, Temperature, Depth (CTD) probe during MSM 82/2 and an expendable sound velocimeter during MSM87. The multibeam data in cruise MSM82/2 were collected from the 11th to 13th of May in 2019 in the headwall area of the Sahara Slide Complex. Only two sound velocities were measured on the 11th and 12th of May, and we applied the measured sound velocities to data from these two days. In the mean time, the measured sound velocity on 12th of May was also applied to data collected on 13th of May. For MSM11/2, sound velocities were adjusted using the mbvelocity tool implemented in the MB-System software. The multibeam bathymetric data were gridded by using the splines with tension algorithm to a final grid with 150 m cell spacing in lateral direction.