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Undersea transmission lines and shoreline AC-DC conversion stations and near-shore transmission lines are being considered as part of a system for transporting energy between the Hawaiian Islands. These facilities will need to be designed so that they will not be damaged or destroyed by coastal or undersea landslides. Advanced site surveys and engineering design of these facilities will require detailed site specific analyses, including sediment sampling and laboratory testing of samples, in situ testing of sediment and rock, detailed charting of bathymetry, and two- or three-dimensional numerical analyses of the factors of safety of the slopes against failure from the various possible loading mechanisms. An intermediate approximate approach can be followed that involves gravity and piston cores, laboratory testing and the application of simplified models to determine a seismic angle of repose for actual sediment in the vicinity of the planned facility. An even simpler and more approximate approach involves predictions of angles of repose using classification of the sediment along a proposed route as either a coarse volcaniclastic sand, a calcareous ooze, or a muddy terrigenous sediment. The steepest slope that such a sediment can maintain is the static angle of repose. Sediment may be found on slopes as steep as these, but it must be considered metastable and liable to fail in the event of any disturbance, storm or earthquake. The seismic angle of repose likely governs most slopes on the Hawaiian Ridge. This declivity corresponds to the response of the slope to a continuing seismic environment. As a long history of earthquakes affects the slopes, they gradually flatten to this level. Slopes that exceed or roughly equal this value can be considered at risk to fail during future earthquakes. Seismic and static angles of repose for three sediment types are tabulated in this report.

Poseidon cruise 518 (leg 1 and 2) took place in the framework of the Horizon 2020 project STEMM-CCS of the EU. The project’s main goal is to develop and test strategies and technologies for the monitoring of subseafloor CO2 storage operations. In this context a small research-scale CO2 gas release experiment is planned for 2019 in the vicinity of the Goldeneye platform located in the British EEZ (central North Sea). Cruise POS518 aimed at collecting necessary oceanographic and biogeochemical baseline data for this release experiment. During Leg 1 ROV PHOCA was used to deploy MPI’s tool for high-precision measurements of O2, CO2 and pH in the bottom water at Goldeneye. In addition, ROV push cores and gravity cores were collected in the area for sediment biogeochemical analyses, and video-CTD casts were conducted to study the water column chemistry. The stereo-camera system and a horizontally looking multibeam echosounder, both, for determining gas bubble emissions at the seafloor were deployed at the Figge Maar blowout crater in the German Bight. Investigations were complemented by hydroacoustic surveys detecting gas bubble leakages at several abandoned wells in the North Sea as well as the Figge Maar. Surface water alkalinity as well as CH4, CO2, and water partial pressures in the air above the sea surface were measured continuously during the cruise. During Leg 2 three different benthic lander systems were deployed to obtain baseline data of oceanographic and biogeochemical parameters for a small research-scale CO2 gas release experiment planned for 2019. The first lander was equipped with an acoustic Doppler current profiler (ADCP), a CTD and an O2 optode. It was deployed for 6 days close to Goldeneye to obtain high resolution data which can be linked to the long-term measurements of the NOC-Lander. This lander is equipped with a suite of sensors to monitor temperature, conductivity, pressure, current speed and direction, hydro-acoustic, pH, pCO2, O2 and nutrients over a period of about 10 months with popup telemetry units for data transmission via IRIDIUM satellite telemetry every 3 months. Two short-term deployments of the Biogeochemical Observatory (BIGO) were conducted to study the molar ratio between oxygen and CO2-fluxes at the seafloor. Sediment cores obtained by gravity and multi corer were collected for sediment biogeochemical analyses and video-CTD casts were used to study the chemistry of the water column.

VESPA was a successful 25 day research cruise on R/V l'Atalante that took place in May and June 2015. The main aim was to acquire new rock samples from extinct volcanoes on the Norfolk, Loyalty and Three Kings ridges, which connect New Caledonia and New Zealand. This was in order to test various hypotheses of Late Cretaceous-Miocene SW Pacific tectonic development relating to (i) nature and duration of magmatism on the ridges; (ii) timing of subduction initiation east of northern Zealandia; (iii) postulated subduction polarity changes. A total of 3400 km of 'sismique rapide' shallow reflection seismic data were acquired and processed onboard. The seismic lines provided a very useful structural-stratigraphic framework for the rock dredging. Combined with multibeam bathymetry data they allowed intelligent targeting of acoustic basement (lavas) and specific seismic reflectors (sedimentary strata) on rocky slopes and fault scarps. Different stratigraphic levels of the Loyalty and Three Kings Ridge volcanic piles were sampled by dredging at different water depths on the Cook Fracture Zone and Cagou Trough fault scarps. By the end of the cruise, 43 dredges had been attempted and 36 of them yielded igneous or sedimentary rocks potentially useful to the VESPA project. Onboard use of a portable X-ray fluorescence unit confirmed the presence of intraplate (but no arc) volcanoes on the Norfolk Ridge and presence of arc, intraplate and shoshonitic volcanoes on the Loyalty and Three Kings Ridges. A total of 770 kg of rock was retained for post-cruise analysis in New Caledonia, France and New Zealand. Future work will include micropaleontological dating of sedimentary rocks, U-Pb and Ar-Ar isotopic dating of igneous rocks, and whole rock geochemical and tracer isotope analyses. We are optimistic that many of the initial research hypotheses will be able to be tested.

Cruise M127 is an integral part of the EU-FP7 project “Blue Mining: Breakthrough Solutions for the Sustainable Deep Sea Mining Value Chain” and is addressing research questions regarding the nature and resource potential of marine minerals, especially seafloor massive sulfides (SMS) along mid-ocean ridges. The cruise left from Bridgetown (Barbados) in the evening of May 25th and reached the working area at 26°N on the Mid-Atlantic Ridge on May 30th (Fig.1.1). One of the main tasks during the cruise was mapping of the TAG segment (26°N) in various resolutions. This included ship-based multibeam mapping over the entire length of the ridge segment as well as high-resolution mapping using an autonomous underwater vehicle (AUV) flying close to the seafloor (40-100 m altitude). The ship-based multibeam mapped along 710 nautical miles of profile lines covering approximately 7,000 km2 in the working area. Another 1,800 nautical miles of lines were mapped on the transit from Barbados to the working area and from there back to the Azores. The AUV was used on 19 missions, usually with survey times close to the seafloor of between 10 and 12 hours. Most dives provided maps with a resolution of 2 m and collected a number of other parameters with its sensors at the same time. Two dives were devoted to mapping points of interest in 50 cm resolution. Seismic work, as the 2nd important part of the cruise, included refraction and reflection seismics with airgun shots and multichannel seismic streamer records being compiled along 49 profiles on 8 survey runs (230 nautical miles in total length). Additionally, 22 ocean bottom seismometers (OBS) and 9 ocean bottom hydrophones (OBH) deployments were undertaken. The seismic work was hampered by problems with the compressor, for which the oil could not be cold enough at the beginning. This was later solved with the help of the ships crew. Deep-towed streamer work could also not be performed because of continued problems with the streamer that could not be resolved on board. A series of 6 ocean bottom electro-magnetic stations (OBEM) were deployed as preparation for the up-coming RRS James Cook cruise, which is also part of the Blue Mining project. A modular towed instrument platform (HYBIS) was used to deploy 10 of the (OBS) to the seafloor with high precision. Since this platform has built-in cameras and can be equipped with a sampling module we used this instrument later in the cruise to further visually inspect the seafloor and select locations for sampling. The final instrument being used was a short (3m) gravity corer for sediment sampling. In the course of the cruise 35 stations were attempted of which 22 stations successfully retrieved sediment for some of which ship-board analyses showed very high concentrations of copper. Rock fragments were recovered in 9 stations indicating the volcanic nature of those sampling stations. At the end of the cruise all Ocean Bottom Seismometers (OBS) were recovered. Only the six OBEM were intentionally left behind. Station work in the working area ended on 20:30 LT on June 23rd when the 5 day transit to Ponta Delgada was started. During the transits from and to the working area 3 ARGO floats were deployed and the ship-based multibeam and the 75-kHz ADCP collected data in international waters. The cruise ended 09:00 LT of June 28th with docking in Ponta Delgada. Overall on 1/3 of the cruise was used for the transit and 2/3 for stations work and transits within the working area (Fig. 1.2). Most of station time was devoted to geophysical work including seismic profiling and the deployment and recovery of the instruments.

Technical report. Contribution to the bathymetric mapping of the Antarctic.

ALKOR cruise AL548 took place as part of the EMFF (European Maritime and Fisheries Fund)-funded project BASTA (Boost Applied munition detection through Smart data inTegration and AI workflows; https://www.basta-munition.eu) and as continuation of the munition monitoring started within the BMBF-funded project UDEMM (Environmental Monitoring for the Delaboration of Munition in the Sea; https://udemm.geomar.de/). In October 2018, a first cruise (POS530 MineMoni2018) was conducted, to gather data for a broad baseline study in the German Baltic Sea. Results show a moderate contamination level on regional and coastal scale, but indicate higher levels for specific local areas. Within UDEMM, expertise was developed to detect, exactly locate and monitor munition (e.g. torpedoes, sea mines, ground mines) on the seafloor using optical and hydroacoustic means. In addition, chemical analyses of dissolved contaminants in the water and sediments was performed. Data acquired during this cruise are used in BASTA, which aims for enhanced munition detection via AUV-based artificial intelligence applied on multi-sensor datasets. At the same time, the project ExPloTect (Ex-situ, near-real-time exPlosive compound deTection in seawater) (also EMFF-funded) addresses the need for an innovative approach to detect explosive compounds in seawater. A prototype system was used and successfully tested for the first time during this cruise. The main focus was placed onto the two already known dumpsites Kolberger Heide and Lübeck Bight. Additionally, new areas Falshöft (Schleswig-Holstein) and Cadet Channel, Trollegrund and Großklützhöved (Mecklenburg-Vorpommern) were explored. In each area high-resolution multibeam mapping was performed and contact lists, indicating potential munition objects were produced on board. AUV surveys were conducted to ground-truth possible contacts via detailed photograph and magnetometer mapping. This was complemented with towed video (TV)-CTD profiles. The transits to and between those sites were planned along former constraint routes during WWII. These routes were main targets of the British Air Force and mines and bombs can be expected along these ways. During transits water samples were taken with on a CTD- (conductivity, temperature, depth) rosette-mounted Niskin bottles in regular distances, in order to obtain a comprehensive understanding munition compounds (inter alia trinitrotoluene (TNT)) measurements across the German Baltic Sea.

Cruise POS500 “LISA” with R/V Poseidon studied the western Ligurian Margin off Southern France, an area in the northeastern part of the western Mediterranean Sea characterized by its active tectonism and frequent mass wasting. The region near the Var estuary close to the city of Nice is particularly suited for landslide research because it represents a natural laboratority where it is possible to study a series of trigger processes of geological and anthropogenic origin. The aim of this MARUM expedition was to: i. Study fresh water seepage in the marine Nice airport landslide and adjacent stable plateau in 15-50 m water depth using water sampling, CTD and geochemistry; ii. Recover and deploy a number of observatories that monitor, pressure, temperature, tilt and seismicity; iii. Run an AUV micro-bathymetric survey with MARUM AUV SEAL5000 to complement existing multibeam maps; and iv. Acquire additional high-resolution seismic reflection profiles to unravel the complex architecture of the Nice slope and Var delta. In a period of approximately two weeks, we acquired valuable geophysical information that helps to understand the evolution of this portion of the Ligurian Margin and further to support an active Amphibious Drilling proposal submitted to ICDP and IODP. We could also show that heavy spring rainfall plus melt water from the French Maritime Alps supplied sufficient hydraulic forcing to push Var aquifer groundwaters to seep into the marine deposits and water column. Freshening was strongest in the 1979 Nice landslide scar, but was also found at the outer edge of the shelf. Recovery and redeployment of various observatory prototypes worked well, both for the MARUM MeBo seafloor drillstring tolos and independent piezometers. Observatory data have yet to be evaluated. In addition, geochemical analyses of bottom waters and pore waters was deferred to shore-based laboratorios except for salinity estimates using a refractometer. Seismic processing was started onboard, but is largely taking place post-cruise at University Bremen.