Description: Multibeam echosounder (MBES) data recorded during RV MARIA S. MERIAN cruise MSM34-1 from 09.12.2013 - 27.12.2013. The main objective of this cruise was the localization and characterization of suitable gas hydrate deposits on the Danube deep-sea fan. 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 RV MARIA S. MERIAN cruise MSM34-1 Kongsberg EM122 multibeam echosounder with a nominal sounding frequency of 11.5 to 12.5 kHz was utilized. 288 beams (and up to 864 soundings in equidistant and dual swath mode) are formed for each ping with a 2°(Tx)/2°(Rx) footprint while the seafloor is detected using amplitude and phase information for each beam sounding. For further information consult https://www.km.kongsberg.com/. Based on the acquisition of 2D seismic lines sufficient overlapping of the outer beams between adjacent profiles was possible. Thus the generation of a very detailed 25 m by 25 m bathymetric survey was possible. Responsible person during this cruise / PI: Jasper Hoffmann (jhoffmann@geomar.de), Ingo Klaucke (GEOMAR). Chief Scientist: Ingo Klaucke CR: https://www.tib.eu/de/suchen/id/awi%3Adoi~10.2312%252Fcr_msm34/ CSR: https://www2.bsh.de/aktdat/dod/fahrtergebnis/2013/20130125.htm

Description: This multibeam echo sounder (MBES) bathymetry data and backscatter data, as well as subbottom profiler data, was acquired in Eckernförde Bay, Germany. The MBES data were acquired using an EM2040c system which was installed on R/V Alkor (Cruise AL447 - 2014). It operates with a 200-400 kHz transducer combined with a CodaOctupus F180 motion sensor. The survey was designed to provide high-resolution bathymetry with 0.5 x 0.5 m resolution. The bathymetry data were post-processed using sound velocity profiles acquired at regular intervals. Tidal corrections were applied using the tidal gauge in Eckernförde with reference to NHN, DHHN92. The backscatter amplitude data were corrected for the variation with grazing angle. We ensured the highest possible resolution by using the raw backscatter time-series data for each footprint (snippets) and compensated for the angle of incidence using reference grids. Subbottom profiler data were acquired with the R/V Alkor and R/V Elisabeth Mann Borgese in late October 2014 (cruise AL447), the beginning of July 2018 (cruise EMB187). The data were acquired using a parametric Innomar SES-2000 medium system creating secondary peak frequencies between 4 and 15 kHz.

Description: Raw multibeam bathymetry data from the Kongsberg EM710 was acquired during the RV Heincke cruise HE576 in the German Bight. The data was generally acquired during calm seas in water depths between ~20 and 50 m. Primarily three different regions were surveyed (Borkumer Reef Ground, Sylt Outer Reef, and Dogger Bank). In some areas, the data is comprehensive and overlapping swaths creating a continuous bathymetry were archived. In other areas the data was acquired complementary to sidescan sonar surveys and individual tracks do not overlap. Data are unprocessed and therefore may contain some incorrect depth measurements (artifacts) without further processing. No tide variations are applied. Sound velocity profiles were acquired regularly. Overall, it appears that the data quality is rather good. The gridded data showed relatively few obstacles.

Description: Multibeam water column data were collected during RV Maria S. Merian cruise MSM31. Multibeam sonar system was Kongsberg EM122. The raw water column sonar data in Kongsberg format (*.wcd) were recorded with Kongsberg SIS software running on Windows operating system. Kongsberg wcd files can be processed using software packages like CARIS HIPS/SIPS, in combination with their corresponding bathymetry (*.all) files.

Description: Multibeam data were collected during RV Maria S. Merian cruise MSM31. Multibeam sonar system was Kongsberg EM1002. Data are unprocessed and may contain outliers and blunders and should not be used for grid calculations and charting projects without further editing. The raw multibeam sonar data in Kongsberg multibeam processing format (*.all) were recorded with Kongsberg SIS software running on Windows operating system. Kongsberg data files can be processed using the software packages CARIS HIPS/SIPS or with the open source software package MB-System.

Description: Multibeam data were collected during RV Maria S. Merian cruise MSM31. Multibeam sonar system was Kongsberg EM122. Data are unprocessed and may contain outliers and blunders and should not be used for grid calculations and charting projects without further editing. The raw multibeam sonar data in Kongsberg multibeam processing format (*.all) were recorded with Kongsberg SIS software running on Windows operating system. Kongsberg data files can be processed using the software packages CARIS HIPS/SIPS or with the open source software package MB-System.

Description: Shallow seabed depressions attributed to focused fluid seepage, known as pock- marks, have been documented in all continental margins. In this study, we dem- onstrate how pockmark formation can be the result of a combination of multiple factors— fluid type, overpressures, seafloor sediment type, stratigraphy and bot- tom currents. We integrate multibeam echosounder and seismic reflection data, sediment cores and pore water samples, with numerical models of groundwa- ter and gas hydrates, from the Canterbury Margin (off New Zealand). More than 6800 surface pockmarks, reaching densities of 100 per km2, and an undefined number of buried pockmarks, are identified in the middle to outer shelf and lower continental slope. Fluid conduits across the shelf and slope include shal- low to deep chimneys/pipes. Methane with a biogenic and/or thermogenic origin is the main fluid forming flow and escape features, although saline and fresh- ened groundwaters may also be seeping across the slope. The main drivers of fluid flow and seepage are overpressure across the slope generated by sediment loading and thin sediment overburden above the overpressured interval in the outer shelf. Other processes (e.g. methane generation and flow, a reduction in hydrostatic pressure due to sea- level lowering) may also account for fluid flow and seepage features, particularly across the shelf. Pockmark occurrence coin- cides with muddy sediments at the seafloor, whereas their planform is elongated by bottom currents.

Description: Rocky reefs provide complex structures in the otherwise largely sand-dominated coastal North Sea. Therefore, these reefs are highly important natural habitats for the functioning of coastal ecosystems, as they provide shelter, refuge and nursery grounds for various mobile and sessile species. In the North Sea, the spatial distribution of these habitats has been intensively investigated over recent years. However, these studies generally provide static accounts of the current state of these reef systems, but limited data exist on the temporal variations in sediment dynamics at and around natural rocky reefs. In this study, we provide observations from a multiannual time series of hydroacoustic seafloor surveys conducted at an isolated rocky reef in the North Sea. We use multibeam bathymetry and side-scan sonar backscatter data in combination with video observations, sediment sampling, and sub-bottom profiler data to assess the long-term variations of the rocky reef system. The reef is located in water depths between 11 and 17 m with an areal extent of ~0.5 km2 and is surrounded by mobile sands. The topography of the rocky reef appears to create a distinct hydrodynamic system that permits mobile sands to settle or move into bathymetrical deeper parts of the reef. Our results suggest a very dynamic system surrounding the reef with large scale scouring, sediment reworking and transport, while the shallower central part of the reef remains stable over time. We demonstrate the importance of hydrodynamics and current scouring around reefs for the local variability in seafloor properties over time. These small-scale dynamics are likewise reflected in the spatial distribution of sessile species, which are less abundant in proximity to mobile sands. The hydroacoustic mapping and monitoring of seafloor dynamics at higher spatial and temporal resolutions presents an important future direction in the study of valuable coastal habitats.

Description: During HE588, data were collected in five research areas in the south-eastern part of the German Bight as part of the DAM Pilotmission on the exclusion of mobile bottom-contact fishing in the North Sea (www.mgf-nordsee.de). The cruise started on October 24, 2021, and had a duration of twelve days at sea. The conducted tasks consisted of seafloor mapping with hydroacoustic devices, multicoring and grab sampling from the seafloor surface, lander deployments for the study of current characteristics, and video and diving surveys of benthic fauna. Despite the unstable weather conditions, all scientific tasks could be conducted successfully within the allocated time.

Description: Voluminous igneous complexes are commonly present in sedimentary basins on volcanic rifted margins, and they represent a challenge for petroleum explorationists. A 2500 km2 industry-standard 3D seismic cube has recently been acquired on the Vøring Marginal High offshore mid-Norway to image subbasalt sedimentary rocks. This cube also provides a unique opportunity for imaging top- and intrabasalt structures. Detailed seismic geomorphological interpretation of the top-basalt horizon, locally calibrated with high-resolution P-Cable wide-azimuth data, reveals new insight into the late-stage development of the volcanic flow fields and the kilometer-high coastal Vøring Escarpment. Subaerial lava flows with compressional ridges and inflated lava lobes cover the marginal high, with a comparable structure and size to modern subaerial lava fields. Pitted surfaces, likely formed by lava emplaced in a wet environment, are present in the western part of the study area near the continent-ocean boundary. The prominent Vøring Escarpment formed when eastward-flowing lava reached the coastline. The escarpment morphology is influenced by preexisting structural highs, and these highs are locally bypassed by the lava. Volcanogenic debris flows are well-imaged on the escarpment horizon, along with large-scale large slump blocks. Similar features exist in active volcanic environments, e.g., on the south coast of Hawaii. Numerous postvolcanic extensional faults and incised channels cut into the marginal high and the escarpment, and we found that the area was geologically active after the volcanism ceased. In summary, igneous seismic geomorphology and seismic volcanostratigraphy are two very powerful methods to understand the volcanic deposits and development of rifted margins. Our study demonstrates great promise for further understanding the igneous development of offshore basins as more high-quality 3D seismic data become available.