Wintersteller, Paul; dos Santos Ferreira, Christian (2016): Gridded bathymetry from multibeam echosounder EM12S data of the cruise TTR6/2 (1996) [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.860025

Bathymetry based on data recorded during TTR6 between 05.07.1996 and 20.08.1996 in the Black Sea. In the central Black Sea, the aim of TTR-6 the investigation was a bathymetric map of a field of mud volcanoes known from the previous TTR cruises, during transit. In the Sorokin Trough, where gas hydrates were earlier obtained from sea bottom sediments the primary goals concerned the elucidation of the structure of clay diapiric folds and the searching for mud volcanoes and other evidence for fluid flux through the seafloor. The task of looking for the seafloor manifestation of deep fluid emanation was set in the Pallas Uplift area. The EM12s surveying on the Caucasian margin was aimed at the construction of the first detailed bathymetric map of this area.

Detailed description:

During the cruise TTR-6, on-board R/V Gelendzhik, the Kongsberg EM12S multi-beam echo-sounder was used to acquire bathymetric data. The EM12S has an angular coverage sector of 90° with 81 beams and uses a low nominal sounding frequency of 13 kHz. Responsible person during this cruise / PI: O.V. Krylov (Former employee of Moscow State University). Link to further informations: http://folk.uio.no/adrianom/TTR%20WWW/TTR/cruises/ttr6.html

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 TTR-6 cruise, these were not sufficient to represent the changes in sound velocity throughout the transit and/or study area, therefore a sound velocity profile (SVP) correction had to be applied. The corrections are based on various SVP and 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 (or 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. Due to a negative offset within the data set a positive draft correction of 10 m as well as a roll offset of 0.15° had to be applied using mbset, while further pitch, heave or heading corrections were not necessary for the TTR-6 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. 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.