Multibeam bathymetry processed data (EM 120 echosounder entire dataset, MB-System data format) of RV MARIA S. MERIAN during cruise MSM20/2

Processed multibeam echosounder (MBES) data recorded during RV MARIA S. MERIAN cruise MSM20-2 between 17.01.2012 and 15.02.2012 around Tristan da Cunha. The Tristan da Cunha hotspot is thought to have played a major role in the rifting of the South Atlantic margins and the creation of the aseismic Walvis Ridge by impinging at the base of the continental lithosphere shortly before or during the breakup of the South Atlantic margins. MSM20-2 staged therefore a multi-disciplinary geophysical study of the Tristan da Cunha hotspot by acquiring passive marine electromagnetic and seismic data, bathymetric data as well as gravity data from which we will derive an electrical resistivity, velocity and density model down to a depth of several hundred kilometers. CI Citation: Paul Wintersteller (seafloor-imaging@marum.de) as responsible party for bathymetry data post-processing, data ingest and approval. The bathymetric post-processing and creation of products were conducted by Janina Kammann (University Hamburg), Anne Strack (University Bremen / MARUM) and the Seafloor-Imaging & Mapping group of University Bremen / MARUM, responsible person: Paul Wintersteller (seafloor-imaging@marum.de). The open source software MB-system suite (Caress, D. W., and D. N. Chayes, MB-System: Mapping the Seafloor, https://www.mbari.org/products/research-software/mb-system, 2017.) was utilized for this purpose. A tide correction was applied, based on the Oregon State University (OSU) tidal prediction software (OTPS) that is retrievable through MB-System. CTD measurements were taken during the cruise, and these were sufficient to represent the changes in the sound velocity throughout the study area. Further roll, pitch and heave corrections were not applied for the MSM20-2 data. Bathymetric data has been manually cleaned for existing artefacts with mbeditviz. With mbmosaic one creates tables of the average amplitude and/or sidescan values as a function of the grazing angle with the seafloor that can be used by the program mbprocess to correct the sidescan or amplitude data for the variation with grazing angle. The mbprocess program applies changes to an extended raw data file annotaded with a "p" like "rawfilename"p.mbXX where XX stands for the MBES type, in case of EM120 it is mb57. The processed files allow further post-processing e.g. raytracing regarding sound velocity correction, gridding on different scales and merging of data on a hydroacoustic level, and are therefor the most valuable and sustainable product of a hydrographers workflow with MB-System. Description of the data source and the raw data itself can be found under: https://doi.org/10.1594/PANGAEA.898376 A composite grid (DTM) of the bathymetry of cruises MSM20-2 and MSM24 is published with the following DOI: https://doi.org/10.1594/PANGAEA.898303

Chief scientist: Marion Jegen-Kulcsar (mjegen@geomar.de) CR: https://doi.org/10.2312/cr_msm20_2 CSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2012/20120063.htm ADCP: https://doi.org/10.1594/PANGAEA.823159