DOI: 10.1594/pangaea.912938
title: Gridded bathymetry from EM122 multibeam echosounder of R/V Maria S. Merian cruise MSM57/1

description: Bathymetry data was acquired during R/V MARIA S. MERIAN cruise MSM57-1 off Svalbard between 29.07.2016 and 12.08.2016. The cruise investigated gas hydrate systems and their dynamics at the continental margin of Svalbard. The key instrument to be used during this expedition was the Bremen deep sea drill rig MeBo. Investigations during leg 1 were concentrated mostly at the Vestnesa Ridge. CI Citation: Paul Wintersteller (seafloor-imaging@marum.de) as responsible party for bathymetry raw data ingest creation of products and approval.Description of data source:During the MSM57/1 cruise, the hull-mounted Kongsberg EM122 multibeam echosounder (MBES) was utilized to perform bathymetric mapping in middle to deep water depths. Two linear transducer arrays in a Mills Cross configuration transmit acoustic signals of a nominal sonar frequency of 12 kHz. With 432 soundings per swath, the emission cone has a dimension of max 150° across track and 2° along track. With a reception obtained from 288 beams, the actual beam footprint is 2° by 2°. Depending on the roughness of the seafloor, the swath width on a flat bottom is generally maximum six times the water depth. For further information on the system, consult https://www.km.kongsberg.com/. The position and depth of the water column is estimated for each beam by using the detected two-way-travel time and the beam angle known for each beam, ray traced through the water column, utilizing a proper sound speed profile. During this cruise the swath width was set to 120° in order to improve data quality by reducing noisy outer beams data and increasing ping rate. The use of the high-density equidistant and the dual-swath mode of the EM122 resulted in up to 864 soundings per ping. The EM122 was running continuously during the cruise with an average vessel speed of about 4.4 kn.Special thanks goes to the MSM57-1watchkeeper: Chieh Wei Hsu, Stefan Bünz and Michael RiedelResponsible person during this cruise / PI: P. Wintersteller (pwintersteller@marum.de).Description of data processing:Postprocessing and products were conducted by the Seafloor-Imaging & Mapping group of MARUM/FB5, responsible person Paul Wintersteller (seafloor-imaging@marum.de). The open source software MB-System (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 during the MSM57-1 were sufficient to represent the changes in the sound velocity throughout the study area. Roll, pitch and heave corrections were not applied to the data. Bathymetric data has been manually cleaned for existing artefacts with mbeditviz. NetCDF (GMT) grids of the product and the statistics were created using mbgrid No total propagated uncertainty (TPU) has been calculated to gather vertical or horizontal accuracy. The currently published bathymetric grid of the cruise has a resolution of 35 m. A higher resolution is, at least partly, achievable. The grid extended with _num represents a raster dataset with the statistical number of beams/depths taken into account to create the depth of the cell. The extended _sd -grid contains the standard deviation for each cell. The DTMs projections are given in Geographic coordinate system Lat/Lon; Geodetic Datum: WGS84. All grids produced are retrievable through the PANGAEA database (www.pangaea.de).Chief Scientist: G. Bohrmann (gbohrmann@marum.de)CR: http://elib.suub.uni-bremen.de/edocs/00105895-1.pdfCSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2016/20160045.htm