Wintersteller, Paul; dos Santos Ferreira, Christian (2016): Gridded bathymetry from multibeam echosounder HS-DS2 data of the cruise M52/1 (2002) [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.860037

Bathymetry based on data recorded during M52-1 between 02.01.2002 and 01.02.2002 in the Black Sea. The cruise was focused on studying the distribution, structure and architecture of gas hydrate deposits in the Black Sea as well as their relationship to fluid migration pathways. While high-resolution geoacoustic investigation tools covering a whole range of frequencies and techniques render detailed images of near-surface gas hydrates and associated fluid migration pathways.

Detailed description:

During the cruise M52-1 the ATLAS Hydrosweep (HS-DS2) multi-beam echo-sounder was used. The HS-DS2 uses a nominal sounding frequency of 15.5 kHz. 59 beams across a 90° angle are formed for each ping while the seafloor is detected using amplitude and phase information for each beam sounding. HS-DS2 multibeam data were continuously recorded as long as R/V METEOR operated during this cruise. Responsible person during this cruise / PI: Wilhelm Weinrebe (wweinrebe@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 M52-1 cruise, these were not sufficient to represent the changes in the sound velocity profile (SVP) throughout the study area, therefore a SVP correction had to be 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. Due to a positive offset within the data set a negative draft correction of 30 m had to be applied (at least partly) with mbset while further roll, pitch, and heave or lever-arms corrections were not necessary for the M72-3 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.