DOI: 10.1594/pangaea.905599
title: Gridded bathymetry from EM710 multibeam echosounder of RV HEINCKE cruise HE387 (Svalbard continental margin)

description: Between 20.08.2012 and 16.09.2012, bathymetric data was acquired in the Arctic west of Svalbard during the cruise HE387 on board R/V HEINCKE, which was aimed at the investigation of gas emissions at the Svalbard continental margin. The main objectives of the cruise were the quantification of the amount of methane that is released as gas bubbles from the seafloor, mapping the distribution of gas emissions and identifying the source of the gas. By utilizing the multibeam echosounder (MBES) KONGSBERG EM710, a bathymetric map of the working area was conducted and water column data was examined for the detection of gas emission sites, providing the basis for their correlation with seafloor morphologies. Furthermore, additional echosounders (SES2000 & EK60) collected subbottom and water column information. Direct, visual and acoustic measurements on the seafloor were conducted through the remotely operated vehicle (ROV) Cherokee (MARUM) to locate and quantify individual gas emission sites and estimate their flux into the ocean. Pore water samples and measurements of dissolved methane in the water column were obtained from hydrocasts and sediment sampling.CI Citation: Paul Wintersteller (seafloor-imaging@marum.de) as responsible party for bathymetry raw data ingest and approval.Description of the data source:During the HE387 cruise, the hull-mounted KONGSBERG EM710 multibeam ecosounder (MBES) was utilized to perform bathymetric mapping. According to the manufacturer, its maximum depth limit is at 2000 m; however, its optimum performance is obtained in shallow to mid water depths of maximum 1000 m. The EM710 operates at sonar frequencies of 70 to 100 kHz. 256 beams (and up to 800 soundings with equidistant and dual swath mode) are formed for each ping with a 1°(Tx)/2°(Rx) footprint. The seafloor is detected using amplitude and phase information for each beam sounding. For further information consult: https://epic.awi.de/id/eprint/33252/1/RV_Heincke_Multibeam_Support.pdf.The position and depth of the water column is estimated for each sounding through the two-way-travel time, beam angle and ray bending due to refraction in the water column by sound speed variations. A problem that occurred during the cruise was a wobbling of the bathymetric data, which persisted throughout the journey even after a calibration of the MBES system at the beginning of the cruise. Most surveys were carried out for the purpose of simultaneous flare mapping and acquisition of bathymetry. The EM710 was running almost continuously in combination with the single beam echosounder EK60. The transmission and recording of subbottom profiler SES2000 caused noise signals in the MBES data and was therefore only used for particular areas of interest.Responsible person during this cruise / PI: Christian dos Santos Ferreira (cferreira@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 suite (Caress, D.W., and D.N. Chayes, MB-System Version 5.5, open source software distributed from the MBARI and L-DEO web sites, 2000-2012.) was utilized for this purpose. A tide correction was applied to the HE387 data. There were no roll, pitch and heave corrections. Using Mbeditviz, artefacts were cleaned manually. NetCDF (GMT) grids of the edited data as well as statistics were created with mbgrid. The published bathymetric grid of the cruise HE387 has a resolution of 10 m. No total propagated uncertainty (TPU) has been calculated to gather vertical or horizontal accuracy. 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. All grids produced are retrievable through the PANGAEA database (www.pangaea.de).Projection: Geographic Coordinate System / WGS84Chief Scientist: Heiko SahlingCR: https://elib.suub.uni-bremen.de/edocs/00103879-1.pdfCSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2012/20120416.htmRaw data: https://doi.org/10.1594/PANGAEA.816220