ALBERT

Description: Sediment echosounder data using Atlas Parasound P70 echosounder was recorded during RV METEOR cruise M134/1. The cruise took place between 16.01.2017 and 18.02.2017 around South Georgia. The main objective of the cruise was to investigate emissions of free gas from cross‐shelf troughs of South Georgia, their distribution, quantification, and sources for methane ebullition sites in sub‐Antarctic waters. Furthermore, the cruise aimed at mapping of the glacial bathymetry on the shelf. By using the parametric sub-bottom profiler PARASOUND next to the multibeam echosounder, emission sites and zones of acoustic blanking within the sediment were detected. CI Citation: Paul Wintersteller (seafloor-imaging@marum.de) as responsible party raw data ingest and approval. Description of data source: During the M134 cruise, the hull-mounted parametric sub-bottom profiler ATLAS PARASOUND P70 was used to conduct information about the sediment sub-surface and water column. Its function is based on the parametric effect of the non-linear relation of pressure and density during sonar propagation. The system utilizes two high-intensity waves with frequencies of 18-20 kHz (primary high frequency; PHF) and 22-24 kHz to create a secondary high (about 40-42 kHz) and secondary low frequency (SLF) of about 4 kHz. The SLF can record sub-bottom structures, whereas the PHF can image the water column and potential gas bubbles, plankton ,fish or nepheloid layers within. The transducer array has an opening angle of 4° by 5°, which corresponds to a footprint size of about 7% of the water depth. Data acquisition was performed using measured real-time values of surface sound velocity and a static sound velocity profile of 1500 m/s. Using the software ATLAS PARASTORE, data was displayed and stored as raw *.asd files and additional *.ps3 and auxiliary files for certain depth windows. The *.ps3 files are utilized for conversion to SEG-Y format and further processing using the software SeNT (developed by V. Spiess & H. Keil, MTU-GeoB) and Kingdom Suite. For further information on the system, consult: https://epic.awi.de/id/eprint/26733/7/ATLAS_PARASOUND_2015-02.pdf The sub-bottom profiler was operating almost continuously and simultaneously with the multibeam echosounder. Responsible persons during this cruise / PI: Wilhelm Weinrebe (wweinrebe@geomar.de) & Paul Wintersteller (pwintersteller@marum.de). Chief Scientist: G. Bohrmann (gbohrmann@marum.de) CR: https://elib.suub.uni-bremen.de/edocs/00106081-1.pdf CSR: http://www.bsh.de/aktdat/dod/fahrtergebnis/2017/20170002.htm A special thanks goes to the watch keeper during M134/1: Viola Bihler, Maximilan Grahs and Nikolas Stange.