dos Santos Ferreira, Christian; Wintersteller, Paul (2016): Gridded bathymetry from multibeam echosounder ELAC BottomChart MkII data of the cruise POS317/3 (2004) [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.860437

Bathymetry based on data recorded during POS317-3 between 19.09.2004 and 13.10.2004 in the Black Sea. This cruise concentrated on bathymetric mapping and mapping of gas seeps by hydro-acoustic detection of gas flares in the water column and the quantification of microbial turnover of gassy sediments and microbial mats. The major objective during POS317-3 was the characterization and identification of microorganisms involved in the anaerobic methane oxidation in the sediment and in microbial mats. As part of these investigations characteristic organic molecules will be identified, which can be used as biomarkers for anaerobic methane oxidizing microorganisms.

Detailed Processing:

During the POS317-3 cruise the ELAC BottomChart MkII system was used, consisting of 50 kHz transducers/receivers which were mounted in the moon pool of the ship. 129 beams are formed for each ping while the seafloor is detected using amplitude and phase information for each beam sounding. For further information, consult http://www.ssrsurvey.com/ssrELACMultibeam.pdf. A total amount of 105 hours was spent for bathymetric mapping during POS317-3 with the ELAC MkII echo-sounder in order to map the Danube canyon and the Paleo-Dnepr area. Responsible person with respect to hydroacoustics during this cruise / PI: Jens Greinert (jgreinert@geomar.de).

Description of data processing:

Postprocessing and products were conducted by the Seafloor-Imaging group of MARUM, responsible person: Paul Wintersteller (seafloor-imaging@marum.de). The open source software MB-system (Caress, D.W., and D.N. Chayes, MB-System Version 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, based on the Oregon State University (OSU) tidal prediction software (OTPS) that is retrievable through MB-System. In general, there is a tide differences of less than 20 cm in the Black Sea. Though CTD measurements were taken during the POS317-3 cruise, these were not sufficient to represent the changes in the SVP profile throughout the study area, therefore a SVP correction was applied. The corrections of sound velocity are based on various SVP/CTD measurements throughout different cruises in the Black Sea within the last 15-20 years. In addition, the NATO Black Sea data base (http://sfp1.ims.metu.edu.tr/ODBMSDB/ODBMSDB.dll/querydb) was consulted for further CTD profiles in the given season/period of the year and in close position to the data set. The CTD data has then been used to calculate SVP by the usage of the UNESCO formula (G.S.K. Wong and S Zhu, Speed of sound in seawater as a function of salinity, temperature and pressure (1995) J. Acoust. Soc. Am. 97(3) pp 1732-1736). The changes in SVP were applied with the mbset function within mbsystem. Motion, lever-arm or offset corrections e.g. for roll, pitch or heading were not necessary. Bathymetric data has been manually cleaned for existing artefacts with mbeditviz. NetCDF (GMT) grids of the product and the statistics were created using mbgrid. Quality assurance was furthermore proven by visual and statistical comparison of crossing survey-lines from different cruises throughout the Black Sea. 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 125 m. A higher resolution is, at least partly, achievable.