ALBERT

Description: An innovative booster is proposed with the aim of increasing the final penetration depth of the OMNI-Max anchor in the clayey seabed with high strength gradient. The booster is attached to the tail of the OMNI-Max anchor, which is beneficial in improving both gravitational and kinetic energies of the hybrid anchor (i.e., booster + OMNI-Max anchor) during installation and can be retrieved after dynamic installation. The present study carried out two categories of large deformation numerical analyses to simulate the dynamic penetration processes of OMNI-Max anchors and hybrid anchors in normally consolidated and lightly overconsolidated clay. The coupled Eulerian–Lagrangian (CEL) approach was used to investigate the effects of impact velocity, booster weight, and soil strength characteristics (including the strain-rate behavior, the strain-softening behavior, and the undrained shear strength) on the final penetration depth of the anchor. Due to the limitations of the CEL approach in simulating the adhesion friction at the anchor–soil interface, a thin layer region method coupled in the computational fluid dynamics (CFD) approach was used to investigate the effect of the friction coefficient at the anchor–soil interface on the final penetration depth of the anchor. Based on numerical simulation results, a comprehensive prediction model based on the anchor total energy was established to rapidly predict the final penetration depth of the OMNI-Max anchor and the hybrid anchor by considering the strain-rate effect, strain-softening effect, and friction coefficient at the anchor–soil interface.

Description: The San Pedro basin (SPB) is located at the south-eastern margin of Hispaniola Island (Dominican Republic and Haiti). It is the largest offshore basin of the Dominican Republic with an extension of 6000 km2. The basin has a maximum water depth of 1600 m and is positioned to the rear of the Muertos Thrust Belt (MTB). The SPB bounds to the West by The Azua basin which has a proven petroleum system and small oil production has been recovered from the Maleno and Higuerito fields. While in the scientific literature the SPB and the Azua basins have been considered as disconnected sedimentary systems, our current study suggests both are shared a common tectonic evolution and therefore the presence of an untested petroleum system in the SPB can be expected. We have carried out a detailed review and synthesis of the onshore systematic geological mapping (SYSMIN I & II Programs) together with the integration of a large volume of sub-surface geophysical data. This includes analysis of 60 exploration wells provided by Banco Nacional de Datos de Hidrocarburos (BNDH) of the Dominican Republic, processing of new 2D multi-channel seismic data from the Spanish Research Project NORCARIBE, re-processing of legacy seismic profiles and interpretation of gravity and magnetic data. Our results led us to propose a new evolution model for the SPB. Basement of both basins consists of Cretaceous sedimentary and volcanic rocks of intra- and back-arc settings. A change in the stress regime in the Campanian led to partial inversion of the basement units favouring the deposition of two main sequences of Campanian to Maastrichtian and Palaeocene? -Eocene age in a submarine foreland setting. Due to collision between the Carbonate Bahamas Province and Hispaniola in middle Eocene, compressional stresses were transferred to the south where Cretaceous and Paleogene sediments were deformed forming the current configuration of MTB and generating a new accommodation space where SPB was developed since Upper Eocene / Oligocene until Present. While the Azua basin was finally exhumed after Miocene/Pliocene, most of SPB continued as an actively subsiding basin. This new model has allowed identification of the main elements of the petroleum system in the SPB basin: a mature Upper Cretaceous source rock and Oligocene to Miocene carbonate and clastic reservoirs interbedded with sealing shales and marls. Main traps (structural and stratigraphic) are of Oligocene to Miocene age and their formation seems to be synchronous to oil generation. While main elements of the petroleum system seem to be present in the basin, timing is a key issue that must be addressed and assessed in any future exploration in the basin.

Description: Landslide deposits offshore many volcanic islands provide evidence of catastrophic lateral collapses. These deposits span a larger volume range than their continental equivalents, and can generate devastating tsunamis. All historical volcanic-island lateral collapses have occurred in arc settings, and have been characterised by rapid failure and efficient tsunami generation. The varied morphology of their deposits is influenced both by lithological properties and the nature of the substrate. Many deposits show evidence of extensive seafloor erosion and transformation into debris flows, and the propagation of frontally-confined sediment deformation beyond and beneath the primary deposit. Mobilised volumes can far exceed that of the initial failure, and accurate deposit interpretation requires internal geophysical imaging and sampling. Around intraplate ocean-island volcanoes, multi-unit turbidites suggest that lateral collapses may occur in discrete stages; although this would reduce their overall tsunamigenic potential, the volumes of individual stages of collapse remain very large. Numerical models of both landslide and tsunami processes in ocean-island settings are difficult to test, and the smaller collapses that typify island arcs are an important focus of research due to their higher global frequency, availability of direct failure and tsunami observations, and a need to better understand the signals of incipient collapse to develop approaches for tsunami hazard mitigation.

Description: Increased human activities—in particular energy generation and land use—have led to atmospheric pollution by the significant emission of greenhouse gases such as carbon dioxide (CO2) and methane. The associated climate change is also affecting the ocean while, at the same time, the ocean plays a fundamental role in mitigating climate change by serving as a major heat and carbon sink. We highlight some of the most salient aspects of climate change impacting the ocean as articulated in the Special Report on the Ocean and Cryosphere in a Changing Climate by the Intergovernmental Panel on Climate Change (IPCC) released in 2019. It shows that the ocean is warming, the global sea level is rising, ocean heatwaves are more frequent, the ocean is becoming more acidic, marine ecology is shifting, levels of dissolved oxygen are reducing and the melting of ocean-terminating glaciers and ice sheets around Greenland and Antarctica is rapidly increasing. From the perspective of meeting the United Nations Sustainable Development Goals, in particular SDG 14, there are strong synergies between promoting climate mitigation and adaptation strategies, which are enshrined in SDG 13 and outlined in more detail by the Paris Agreement. Scientific research and solution-oriented knowledge generation require the growth and transformation of the science system. Specifically, they will require more freely shared ocean data, new and more effective ways of analyzing observational data fused with ocean and climate models, and enhanced timely assessment, predictions and scenario development of future ocean conditions. At the same time, knowledge from natural and social sciences, as well as informal knowledge, must be considered. Ocean science must be in a position to support decision makers by providing knowledge and frameworks to weigh the ecological, environmental and human impacts with an expected increase in use of the ocean for different sustainable development pathways. In recognition of this challenge, the United Nations declared 2021–2030 as the Decade of Ocean Science for Sustainable Development in order to advance “the science that we need for the ocean we want”. The ocean decade seeks to catalyze a change towards more international, shared and solution-oriented ocean science.

Description: Since the sunlight only penetrates a few hundred meters into the ocean, deep-diving robots have to bring their own light sources for imaging the deep sea, e.g., to inspect hydrothermal vent fields. Such co-moving light sources mounted not very far from a camera introduce uneven illumination and dynamic patterns on seafloor structures but also illuminate particles in the water column and create scattered light in the illuminated volume in front of the camera. In this scenario, a key challenge for forward-looking robots inspecting vertical structures in complex terrain is to identify free space (water) for navigation. At the same time, visual SLAM and 3D reconstruction algorithms should only map rigid structures, but not get distracted by apparent patterns in the water, which often resulted in very noisy maps or 3D models with many artefacts. Both challenges, free space detection, and clean mapping could benefit from pre-segmenting the images before maneuvering or 3D reconstruction. We derive a training scheme that exploits depth maps of a reconstructed 3D model of a black smoker field in 1400 m water depth, resulting in a carefully selected, ground-truthed data set of 1000 images. Using this set, we compare the advantages and drawbacks of a classical Markov Random Field-based segmentation solution (graph cut) and a deep learning-based scheme (U-Net) to finding free space in forward-looking cameras in the deep ocean.

Description: Nowadays underwater vision systems are being widely applied in ocean research. However, the largest portion of the ocean - the deep sea - still remains mostly unexplored. Only relatively few image sets have been taken from the deep sea due to the physical limitations caused by technical challenges and enormous costs. Deep sea images are very different from the images taken in shallow waters and this area did not get much attention from the community. The shortage of deep sea images and the corresponding ground truth data for evaluation and training is becoming a bottleneck for the development of underwater computer vision methods. Thus, this paper presents a physical model-based image simulation solution, which uses an in-air texture and depth information as inputs, to generate underwater image sequences taken by robots in deep ocean scenarios. Different from shallow water conditions, artificial illumination plays a vital role in deep sea image formation as it strongly affects the scene appearance. Our radiometric image formation model considers both attenuation and scattering effects with co-moving spotlights in the dark. By detailed analysis and evaluation of the underwater image formation model, we propose a 3D lookup table structure in combination with a novel rendering strategy to improve simulation performance. This enables us to integrate an interactive deep sea robotic vision simulation in the Unmanned Underwater Vehicles simulator. To inspire further deep sea vision research by the community, we release the source code of our deep sea image converter to the public (https://www.geomar.de/en/omv-research/robotic-imaging-simulator).

Description: In deep water conditions, vision systems mounted on underwater robotic platforms require artificial light sources to illuminate the scene. The particular lighting configurations significantly influence the quality of the captured underwater images and can make their analysis much harder or easier. Nowadays, classical monolithic Xenon flashes are gradually being replaced by more flexible setups of multiple powerful LEDs. However, this raises the question of how to arrange these light sources, given different types of seawater and-depending-on different flying altitudes of the capture platforms. Hence, this paper presents a rendering based coarse-to-fine approach to optimize recent multi-light setups for underwater vehicles. It uses physical underwater light transport models and target ocean and mission parameters to simulate the underwater images as would be observed by a camera system with particular lighting setups. This paper proposes to systematically vary certain design parameters such as each LED’s orientation and analyses the rendered image properties (such as illuminated image area and light uniformity) to find optimal light configurations. We report first results on a real, ongoing AUV light design process for deep sea mission conditions.

Description: Volcanic passive margins are an end-member of continental rifted margins and are believed to originate from the breakup of a continent under the influence of a mantle plume. In spite of 40 y of research into this phenomenon, it is still unknown how excess magmatism is produced and what controls its surprisingly short duration. Expedition 396 will revisit the mid-Norwegian margin 36 y after Ocean Drilling Program Leg 104. It will provide the necessary observations to parameterize comprehensive 3-D numerical models. These will allow us to identify the relative importance of different tectonomagmatic processes. Furthermore, drilling will test the predictions of volcanic seismic facies models and elucidate the role of breakup volcanism in rapid global warming. Secondary objectives relate to the onset of the meridional overturning circulation in the North Atlantic Gateway and the potential to use the breakup basalt province to store carbon dioxide on industrial scales. To this end, Expedition 396 will attempt to drill nine boreholes on the Vøring and Møre margins. They will target the breakup volcanic successions as well as the overlying postrift sediments and the underlying synrift sediments. In conjunction with the wealth of reflection seismic data collected by the hydrocarbon industry during the past 40 y, the new borehole information will provide an unprecedented picture of the formation of a large igneous province during the opening of an ocean basin.

Description: AL552 Erster Wochenbericht (Berichtszeitraum 16.3.-22.3.2021)

Description: (GPF 21-1_013) Helgoland Pockmarks - GEOMAR / CAU Kiel, 26.03. - 05.04.2021, Emden - Emden

Description: Fahrtabschnitt 06.03. – 13.03.2021

Description: The 2014 Mw 8.1 Iquique earthquake ruptured the boundary between the subducting Nazca Plate and the overriding South American Plate in the North Chilean subduction zone. The broken segment of the South American subduction zone had likely accumulated elastic strain since an M~9 earthquake in 1877 and what therefore considered a mature seismic gap. The moderate magnitude of the 2014 earthquake and its compact rupture area, which only broke the central part of the seismic gap, did not result in a significant tsunami in the Pacific Ocean. To investigate the seismo-tectonic segmentation of the North Chilean subduction zone in the region of the 2014 Iquique earthquake at the shallow seismic/aseismic transition, we combine two years of local aftershock seismicity observations from ocean bottom seismometers and long- offset seismic reflection data from the rupture area. Our study links short term deformation associated with a single seismic cycle to the permanent deformation history of an erosive convergent margin over millions of years. A high density of aftershocks following the 2014 Iquique earthquake occurred in the up-dip region of the coseismic rupture, where they form a trench parallel band. The events spread from the subducting oceanic plate across the plate boundary and into the overriding continental crust. The band of aftershock seismicity separates a pervasively fractured and likely fluid-filled marine forearc farther seaward from a less deformed section of the forearc farther landward. At the transition, active subduction erosion during the postseismic and possibly coseismic phases of the 2014 Iquique earthquake leads to basal abrasion of the upper plate and associated extensional faulting of the overlying marine forearc. Landward migration of the seismogenic up-dip limit, possibly at similar rates compared to the trench and the volcanic arc, leaves behind a heavily fractured and fluid-filled outermost forearc. This most seaward part of the subduction zone might be too weak to store sufficient elastic strain to nucleate a large megathrust earthquake.

Description: FS Alkor Reise 556, Fahrtabschnitt 14.05. - 22.05.2021 Die Ostsee hat im Rahmen des Klimawandels und wachsender anthropogener Nutzung in den letzten 50 Jahren tiefgreifende und im globalen Vergleich besonders schnell ablaufende Veränderungen, wie Erwärmung, Versauerung, Eutrophierung, zunehmenden Sauerstoffmangel, Überfischung, und die Ausbreitung invasiver Arten, erfahren. Die ökologischen und ökonomischen Konsequenzen dieser langfristigen Veränderungen sind durch kurzfristige Projekte nur schwer zu verfolgen. Umso wichtiger sind Langzeitdatenreihen, die auch dekadische Muster abbilden. Das Hauptziel der Ausfahrt AL556 ist es, durch Probennahmen und hydrographische Messungen eine der besten verfügbaren Langzeitdatenreihen für die pelagische Ostsee fortzusetzen. So wurden seit 1986 in den tiefen Becken der Ostsee mit Hauptfokus auf dem Bornholmbecken mit konsistenter Methodik pelagische Schleppnetzfischerei und Fischprobennahmen, Beprobungen des pelagischen Nahrungsnetzes (Phyto- und Zooplankton einschließlich Ichthyo- und gelatinösem („Quallen“) Plankton), ozeanographische/hydrographische Messungen und Hydroakustikaufnahmen durchgeführt. Diese Arbeiten werden während der AL556 weitergeführt, wobei die Ausfahrt aufgrund einer Corona-bedingten Unterbrechung der Langzeitdatenreihe in 2020 von besonderer Bedeutung ist. Die gewonnenen Proben und Daten sind dabei für verschiedene Projekte und internationale Kollaborationen der Abteilung „Marine Evolutionary Ecology“ am GEOMAR relevant. Dazu gehören insbesondere das Projekt "Fischereiindizierte Evolution" im Rahmen der DFG-Graduiertenschule TransEvo (CAU /GEOMAR), und das EU Horizon 2020 Projektes GoJelly. Sonderprojekte in 2021 sind zudem die Isolation von marinen Viren und der Phytoyplanktonart Ostreococcus für das Projekt Marine Mikroben und Viren der Ostsee unter dem Einfluß des Klimawandels und Probennahmen für die Untersuchung der Nahrungsökologie von Fischlarven und planktivoren adulten Fischen mit Hilfe molekularbiologischer Ansätze („Metabarcoding“).

Description: Seabed telecommunication cables can be damaged or broken by powerful seafloor flows of sediment (called turbidity currents), which may runout for hundreds of kilometres into the deep ocean. These flows have the potential to affect multiple cables near-simultaneously over very large areas, so it is more challenging to reroute traffic or repair the cables. However, cable-breaking turbidity currents that runout into the deep ocean were poorly understood, and thus hard to predict, as there were no detailed measurements from these flows in action. Here we present the first detailed measurements from such cable-breaking flows, using moored-sensors along the Congo Submarine Canyon offshore West Africa. These turbidity currents include the furthest travelled sediment flow (of any type) yet measured in action on Earth. The SAT-3 (South Atlantic 3) and WACs (West Africa Cable System) cables were broken on 14-16th January 2020 by a turbidity current that accelerated from 5 to 8 m/s, as it travelled for 〉 1,130 km from river estuary to deep-sea, although a branch of the WACs cable located closer to shore survived. The SAT-3 cable was broken again on 9th March 2020 due to a second turbidity current, this time slowing data transfer during regional coronavirus (COVID-2019) lockdown. These cables had not experienced faults due to natural causes in the previous 19 years. The two cable-breaking flows are associated with a major flood along the Congo River, which produced the highest discharge (72,000m3) recorded at Kinshasa since the early 1960s, and this flood peak reached the river mouth on ~30th December 2019. However, the cable-breaking turbidity currents occurred 2-10 weeks after the flood peak and coincided with unusually large spring tides. Thus, the large cable-breaking flows in 2020 are caused by a combination of a major river flood and tides; and this can provide a basis for predicting the likelihood of future cable-breaking flows. Older (1883-1937) cable breaks in the Congo Submarine Canyon occurred in temporal clusters, sometimes after one or more years of high river discharge. Increased hazards to cables may therefore persist for several years after one or more river floods, which cumulatively prime the river mouth for cable-breaking flows. The 14-16th January 2020 flow accelerated from 5 to 8 m/s with distance, such that the closest cable to shore did not break, whilst two cables further from shore were broken. The largest turbidity currents may increase in power with distance from shore, and are more likely to overspill from their channel in distal sites. Thus, for the largest and most infrequent turbidity currents, locations further from shore can face lower-frequency but higher-magnitude hazards, which may need to be factored into cable route planning. Observations off Taiwan in 2006-2015, and the 2020 events in the Congo Submarine Canyon, show that although multiple cables were broken by fast (〉 5 m/s) turbidity currents, some intervening cables survived. This indicates that local factors can determine whether a cable breaks or not. Repeat seabed surveys of the canyon-channel floor show that erosion during turbidity currents is patchy and concentrated around steeper areas (knickpoints) in the canyon profile, which may explain why only some cables break. If possible, cables should be routed away from knickpoints, also avoiding locations just up-canyon from knickpoints, as knickpoints move up-slope. This study provides key new insights into long runout cable-breaking turbidity currents, and the hazards they pose to seafloor telecommunication cables.

Description: Offshore groundwater systems have been suggested as unconventionalsources of portable water in islands and densely populated coastal regions, where terrestrial groundwater resources are over-extracted or contaminated. In this study, we evaluate how well pore-water salinity can be efficiently estimated from controlled-source electromagnetic (CSEM) resistivity models. Time-domain CSEM methods are an effective tool to explore offshore groundwater bodies since the electrical resistivity of the seafloor is primarily determined by the characteristics of the pore-water within the sub-surface sediments. We integrate offshore TD-CSEM data with borehole data and multichannel seismic reflection to identify an offshore groundwater system in the Canterbury Bight. The Canterbury margin is located off the eastern coast of the South Island of New Zealand and was previously investigated during IODP Expedition 317 in which a pore-fluid salinity anomaly was recorded in borehole U1353. By focusing on the low-salinity zone, we carry out synthetic modelling, implement Bayesian inversion to derive probability density functions for resistivity as a function of depth, and finally transform it to distribution of probability density for pore-fluid salinity using Archie’s equation. Subsequently, we use a trans-dimensional Bayesian inversion to interpret measured CSEM data, and consequently use the derived probability density functions to estimate uncertainty of pore-water salinity. Having done the same procedure for different waypoints in the Canterbury Bight, we extrapolate salinity values on a basin scale and estimate the probability density distribution for pore-water salinity as a function of depth. We show that using the Bayesian sampling algorithm provides us with a more precise estimation of hydrogeological model parameters with their uncertainties by generating an ensemble of models instead of inferring only one model using deterministic inversion approaches.

Description: Cruise SO255 of the German Research Vessel SONNE surveyed the Kermadec Arc System from ca 35°S to 28°S in 2017. Volcanic rocks were obtained by dredge from the Neogene Colville and Kermadec ridges that represent the split remnants of the preceding Vitiaz Arc, the Havre Trough backarc and Quaternary volcanic centers of the Kermadec Arc. The overarching goal of SO255 "VITIAZ" is to elucidate the physical and chemical conditions that control the development of subduction zones, including evolution of mature arc systems, and the transition from arc splitting to back-arc basin generation. The correlated dataset reports major element data for 317 samples, trace element data for 285 samples, radiogenic Sr-Nd-Pb isotope ratios for 155 samples and radiogenic Hf isotope ratios for 88 samples. These include eight topic related samples of cruises TAN0206, TAN1611 of the New Zealand research vessel TANGAROA and one sample of cruise B30 of the Russian research vessel VOLCANOLOG.

Description: Crustose coralline algae (CCA) are susceptible to global change and ocean acidification through changes in seawater carbonate chemistry due to their calcium carbonate cellular structure. In southern Chilean fjords, rainwater and ice melt create a freshwater lens overtop of a marine layer and due to a lack of vertical mixing, these areas remain stratified much of the year. Stratification creates different salinity and carbonate chemistry regimes in the surface and deeper waters. Observations of CCA absence at shallower depths (0-5 m) on the walls of the Comau Fjord and presence at deeper depths (~ 33% cover) lead to questions using field and laboratory analyses to ascertain the effects of freshwater input on CCA distributions within the fjord. Cobbles with Lithothamnion glaciale and other CCA crusts were transplanted from 20 m to 5 m for 9 months to compare pigmentation and physiology of control and transplanted specimens. Transplant experiments revealed tolerance to the surface water conditions in L. glaciale, but near mortality of other CCA species (22% vs. 65% of pigmented areas lost respectively). Water samples taken from 0-20 m in austral autumn and summer and calculated Ωarag levels highlighted stratification within the fjord. While autumn Ωarag levels did not fall below equilibrium at any depth, summer samples were below equilibrium in the surface waters (0.20) creating conditions that negatively affect CCA physiology and their distribution within the Comau Fjord. These results inform us how distributions may vary with global climate change and reduced ocean Ωarag levels.

Description: Invasive species are holobionts and during the invasion process they are accompanied by associated microbiota. In the course of the introduction process extreme conditions during transport and exposure to different conditions in a novel environment may induce holobiont disturbance. Upon introduction, the macroalgal holobiont interacts with microbiota from the new environment and reconfigures new functional microbial communities. As not all microbes may have survived, microbiota from the new environment may replace certain microbes from the native environment. Therefore, flexibility of the seaweed host towards environmental microbiota –or host promiscuity– may be an important trait in macroalgal invasions. Here, we simulated an introduction event in an experimental setting, using the invasive macroalga Agarophyton vermiculophyllum as a model. Individuals from geographically distant populations were transplanted to a common garden in the lab and subjected to a holobiont disturbance treatment followed by exposure to a new source of microbes. This treatment induced strong changes in associated microbiota, which shifted irreversibly in terms of composition and diversity, but recovered functionally in most respects. Moreover, beta-diversity strongly decreased in treated holobionts, indicating that different populations configured more common microbial communities in the common garden. In non-native populations this decline was more rapid and more pronounced, while microbial communities of native populations remained more similar to communities observed in the field. These results demonstrate that non-native A. vermiculophyllum are more flexible to environmental microbes, suggesting that an intra-specific increase in host promiscuity may have promoted the invasion process of A. vermiculophyllum.

Description: Remobilization of soil carbon as a result of permafrost degradation in the drainage basin of the major Siberian rivers combined with higher precipitation in a warming climate potentially increase the flux of terrestrial derived dissolved organic matter (tDOM) into the Arctic Ocean. The Laptev (LS) and East Siberian Seas (ESS) receive enormous amounts of tDOM-rich river water, which undergoes at least one freeze-melt cycle in the Siberian Arctic shelf seas. To better understand how freezing and melting affect the tDOM dynamics in the LS and ESS, we sampled sea ice, river and seawater for their dissolved organic carbon (DOC) concentration and the colored fraction of dissolved organic matter. The sampling took place in different seasons over a period of 9 years (2010–2019). Our results suggest that the main factor regulating the tDOM distribution in the LS and ESS is the mixing of marine waters with freshwater sources carrying different tDOM concentrations. Of particular importance in this context are the 211 km3 of meltwater from land-fast ice from the LS, containing ~ 0.3 Tg DOC, which in spring mixes with 245 km3 of river water from the peak spring discharge of the Lena River, carrying ~ 2.4 Tg DOC into the LS. During the ice-free season, tDOM transport on the shelves takes place in the surface mixed layer, with the direction of transport depending on the prevailing wind direction. In winter, about 1.2 Tg of brine-related DOC, which was expelled from the growing land-fast ice in the LS, is transported in the near-surface water layer into the Transpolar Drift Stream that flows from the Siberian Shelf toward Greenland. The actual water depth in which the tDOM-rich brines are transported, depends mainly on the density stratification of the LS and ESS in the preceding summer and the amount of ice produced in winter. We suspect that climate change in the Arctic will fundamentally alter the dynamics of tDOM transport in the Arctic marginal seas, which will also have consequences for the Arctic carbon cycle.

Description: TRANSFORMERS ; Emden, Deutschland (11.01.2021) – Emden, Deutschland (14.02.2021)

Description: SO277 OMAX served two scientific projects. The objectives of the first project, SMART, were to develop multi-disciplinary methodologies to detect, quantify, and model offshore groundwater reservoirs in regions dominated by carbonate geology such as the Mediterranean Sea. To this end we acquired controlled-source electromagnetic, seismic, hydroacoustic, geochemical, seafloor imagery data off Malta. Preliminary evaluation of the geophysical data show that there are resisitivity anomalies that may represent offshore freshwater aquifers. The absence of evidence for offshore springs means that these aquifers would be confined and that it will be difficult to use them in a sustainable manner. The objective of the second project, MAPACT-ETNA, is to monitor the flank of Etna volcano on Sicily which is slowly deforming seaward. Here, we deployed six seafloor geodesy stations and six ocean bottom seismometers for long-term observation (1-3 years). In addition, we mapped the seafloor off Mt. Etna and off the island of Stromboli to constrain the geological processes that control volcanic flank stability.

Description: Fahrtabschnitt 31.01. - 01.02.2021

Description: TRANSFORMERS ; Emden, Deutschland (11.01.2021) – Emden, Deutschland (14.02.2021)

Description: Globale Modellierungsstudien zeigen, dass direkt vor den Küsten aller Kontinente sehr große Grundwasservorkommen im Meeresboden vorhanden sind. Da die meisten Megacitys und die am schnellsten wachsenden Städte an Küsten liegen, wecken diese Grundwasservorkommen Begehrlichkeiten – vor allem bei zunehmender Trinkwasserknappheit. Wissenschaftler*innen des GEOMAR entwickeln Technologien, mit denen man diese Vorkommen identifizieren und untersuchen kann. Sie gehen den Fragen nach, wie diese Vorkommen entstehen, ob sie mit Grundwasserschichten an Land verbunden sind und ob man sie tatsächlich nachhaltig nutzen kann. Dazu arbeiten sie in Projekten wie SMART, MARCAN oder PRINCE mit Kolleg*innen aus aller Welt zusammen. Was sich hinter diesen Namen genau verbirgt und wie der Stand der Forschung zu OffshoreGrundwasser aktuell ist, das erklärt Dr. Marion Jegen vom GEOMAR in ihrem Online-Vortrag „Grundwasser unter dem Meer – eine Chance für trockene Küstenregionen?“

Description: In this workshop you will get an individual consultation with the GEOMAR librarian, Barbara Schmidt, and the GEOMAR data manager, Hela Mehrtens. Contents: - Make your publications and data more accessible while staying legal. - Learn about specific legal frameworks of the top journals in YOUR field for future publications. - Publication of data: When? Where? Why? How? - Address questions like "What does it mean to make my data open access?", "How to cite data?".

Description: Modern digital scientific workflows - often implying Big Data challenges - require data infrastructures and innovative data science methods across disciplines and technologies. Diverse activities within and outside HGF deal with these challenges, on all levels. The series of Data Science Symposia fosters knowledge exchange and collaboration in the Earth and Environment research community.

Description: (GPF 21-1_013) Helgoland Pockmarks - GEOMAR / CAU Kiel, 26.03. - 05.04.2021, Emden - Emden

Description: The 2014 Mw 8.1 Iquique earthquake ruptured the boundary between the subducting Nazca Plate and the overriding South American Plate in the North Chilean subduction zone. The broken segment of the South American subduction zone had likely accumulated elastic strain since an M~9 earthquake in 1877 and what therefore considered a mature seismic gap. The moderate magnitude of the 2014 earthquake and its compact rupture area, which only broke the central part of the seismic gap, did not result in a significant tsunami in the Pacific Ocean. To investigate the seismo-tectonic segmentation of the North Chilean subduction zone in the region of the 2014 Iquique earthquake at the shallow seismic/aseismic transition, we combine two years of local aftershock seismicity observations from ocean bottom seismometers and long-offset seismic reflection data from the rupture area. Our study links short term deformation associated with a single seismic cycle to the permanent deformation history of an erosive convergent margin over millions of years. A high density of aftershocks following the 2014 Iquique earthquake occurred in the up-dip region of the coseismic rupture, where they form a trench parallel band. The events spread from the subducting oceanic plate across the plate boundary and into the overriding continental crust. The band of aftershock seismicity separates a pervasively fractured and likely fluid-filled marine forearc farther seaward from a less deformed section of the forearc farther landward. At the transition, active subduction erosion during the postseismic and possibly coseismic phases of the 2014 Iquique earthquake leads to basal abrasion of the upper plate and associated extensional faulting of the overlying marine forearc. Landward migration of the seismogenic up-dip limit, possibly at similar rates compared to the trench and the volcanic arc, leaves behind a heavily fractured and fluid-filled outermost forearc. This most seaward part of the subduction zone might be too weak to store sufficient elastic strain to nucleate a large megathrust earthquake.

Description: Traceability and reliable results are the two pillars of analytical methods; certified reference materials (CRMs) meet this requirement. ISO 17034:2016 credentials provide brief information on general requirements for the competence of Reference Material Producers (RMPs). The different types of CRMs have been produced in recent years for chemical analysis in food, water, soil, and sediment matrices in recent years. This review provides a detailed overview of the development of CRMs in the field of marine environment, as matrix CRMs play an important role in the field of environmental monitoring. COMAR database, EVISA database: materials, LGC standards, and JRC catalogs are very helpful online resources to find various types of CRMs according to the application requirements. Highlights - The classification of certified reference materials (CRMs) in the field of marine environment is presented; - General information about the production and characteristics of CRMs is discussed; - Examples of use of existing marine CRMs are described in detail; - Importance of CRMs for QA/QC and CRMs development for chemical analysis is presented; - The parameters that characterize the CRMs: representativeness, homogeneity, stability, and certified value are provided.

Description: FS METEOR Expedition M175 „Transformers II“, 14. - 20. Juni 2021

Description: At the Australian-Pacific plate boundary, the northern Lau Basin is one of the fastest opening back-arc basins on earth. The current configuration of micro-plates, plate boundaries and motions within the northern Lau Basin is quite well understood, but in the southern part of the Lau Basin questions remain about the crustal structure. Here, the Central Lau Spreading Center (CLSC) and the southern tip of the Fonualei Rift and Spreading Center (FRSC) define the diffuse southern boundary of the Niuafo’ou microplate. It remains unclear where the southern plate boundary is located and what kind of boundary it is.We present 1) seismic refraction data of a 200-km long, E-W transect acquired in the transition zone from the eastern side of the CLSC to the southern tip of the FRSC and 2) seismic reflection data of four E-W profiles of varying length, acquired in both the southern part of the Niuafo’ou microplate and the transition in between the CLSC and the FRSC. The seismic data acquisition was accompanied by parametric sediment echosounder, gravimetric and magnetic measurements and was complemented by heat flow probes and dredged samples of the seafloor in the vicinity of the profile.Our travel time tomography reveals a pronounced lateral variation in seismic P-wave velocities from west to east, within the 7-8 km thick back-arc crust. Towards the east, the crust gradually thickens to 13 km of arc crust. The reflection seismic data reveals sediment pockets, varying between 300m to 1000m depth, located on both the thinner back-arc crust and thicker arc crust. In the abyssal regions, faults that cross-cut the basement, but do not reach the surface, are observed on all reflection seismic profiles and are considered inactive today. Towards the west of the profiles, faults reach the surface and are considered active. Rock sampling from this area retrieved predominantly massive aphyric basalts from the back-arc crust in the west. Olivine-rich basalts, andesites, and a broad spectrum of volcaniclastic rocks are the most common rock-type collected from the arc crust in the east.The lack of a thinner crust near the southern tip of the FRSC, the presence of inactive faults that cross-cut the basement, and the presence of active faults in the CLSC suggest that the southern plate boundary of the Niuafo’ou microplate accommodated extension in a wide-rift tectonic setting in the past. Today, this extension is accommodated in the CLSC in a narrow extensional tectonic setting.

Description: The Lau Basin is a young back-arc basin steadily forming at the Indo-Australian-Pacific plate boundary, where the Pacific plate is subducting underneath the Australian plate along the Tonga-Kermadec island arc. As a result of the asymmetric roll back of the Pacific plate, the Lau basin’s divergence rates decline southwards hence dictating an asymmetric, V-shaped basin opening. Further, the decentralisation of the extensional motion over 11 distinct spreading centres and zones of active rifting has led to the formation of a composite crust formed of a microplate mosaic. One of these centres of extensional motion, and the subject of this study, are two overlapping spreading centres (OLSC), the southern tip of the eastern axis of the Mangatolu Triple Junction (MTJ-S) and the northern tip of the Fonualei Rift spreading centre (FRSC).In 2018, the research vessel Sonne (cruise SO267) set out to conduct seismic refraction and wide-angle reflection data along a 185 km long transect crossing the Lau Basinat ~16 °S from the Tonga arc in the east, the overlapping spreading centres, FRSC1 and MTJ-S2, and extending as far as a volcanic ridge in the west. Additionally, 2D MCS reflection seismic data as well as magnetic and gravimetric data were acquired.The results of our Monte-Carlo P-wave traveltime tomography show a crust that varies between 4.5-6 km in thickness. Underneath the OLSC the upper crust is 2-2.5 km thick and the lower crust 2-2.5 km thick. The velocity gradients of the upper and lower crust differ significantly from tomographic models of magmatically dominated oceanic ridges. Compared to such magmatically dominated ridges, our final P-wave velocity model displays a decreased velocity gradient in the upper crust and an increased velocity gradientin the lower crust more comparable to tectonically dominated rifts with a sparse magmatic budget.The dominance of crustal stretching in the regional rifting process leads to a tectonical stretching, thus thinning of the crust under the OLSC and thereforeincreasing the lower crust’s velocity gradient. Due to the limited magmatic budget of the area, neither the magnetic anomaly nor the gravity data indicate a magmatically dominated spreading centre. We conclude that extension in the Lau Basin at the OLSC at 16 °S is dominated by extensional processes with little magmatism, which is supported by the distribution of seismic events concentrated at the northern tip of the FRSC.

Description: About 25% of the Earth’s mid-ocean ridges spread at ultraslow rates of less than 20 mm/yr. However, most of these ultraslow spreading ridges are located in geographically remote areas, which hamper investigation. Consequently, how the crust forms and ages at such spreading centres, which traditionalmodels predict to be magma-starved and cold, remains poorly understood. One of the most accessible ultra-slow spreading centres is the Mid Cayman Spreading Centre (MCSC), in the Caribbean Sea, with spreading rates of ~15-17 mm/yr.CAYSEIS project was proposed to survey the Cayman Trough area in order to obtain new data that constraints the nature of the crust, tectonic structures, lithologies outcropping and hydrothermal processes taking place in this area. Understanding the sub-seabed geophysical structure of the MCSC is key to understanding not only the lithologies and structures exposed at the seabed, but more fundamentally, how they are related at depth and what role hydrothermal fluid flow plays in the geodynamics of ultraslow spreading. CAYSEIS was a joint and multidisciplinary programme of German, British and US American top tier scientists designed for the obtaining of a new high-quality dataset, including 3D Wide-Angle Seismic (WAS), magnetic, gravimetric and seismological data.During the CAYMAN project, we took leverage of the CAYSEIS dataset to invert a 3D tomographic model of the Cayman Trough lithosphere using the Tomo3D code (Meléndez et al., 2015; 2019). This is one of the first times that the Tomo3D code is used for 3D inversion of real datasets. Thus, we are checking our results comparing them with tomographic inversions of 2D lines and testing the different parameters to obtain the more accurate and higher resolution model as possible. The results of this experiment will show not only the lithospheric structure along and across the MSCS, including the exhumed Ocean Core Complexes in the surrounding areas, but the 3D lithospheric configuration of the region which is important to understand the crustal formation processes and the evolution of ultra-slow spreading settings.

Description: Combined analysis of multiple geophysical methods is a key practice to reduce model uncertainties and improve geological interpretations. Various approaches to combine several data sets or physical models in joint inversion have different advantages and challenges. We present a comparison of two ways to integrate marine magnetotelluric (MT) with gravity data along the Namibian passive continental margin and also compare them to a single-method MT inversion. This study area offers an excellent setting, because multiple tectonic processes (e.g. rifting, magmatism, post-breakup sedimentation) lead to various lithological units with distinct physical properties (e.g. continental-, transitional-, and oceanic crust, fault systems or sedimentary depocenters). The two joint inversions are a cross-gradient coupled 3D inversion of marine magnetotelluric data with a fixed structural density model based on gravity modeling, and a joint inversion of the same MT data with satellite gravity data. Structural coupling with the blocky density model enforces harsh resistivity changes in an otherwise smooth model and helps reducing excessively smeared inversion artifacts. Although the edge-like features complicate direct model interpretation, they indicate alternative ways to fit the MT data, while simultaneously matching seismic observations integrated in the density cross-model. For the second approach, the large solution space of the satellite gravity data inversion limits the improvements through joint inversion compared to a single method MT inversion. The resulting joint inversion resistivity model differs only marginally from the single-method resistivity model, while the joint density model inherits some of the rather questionable resistivity model features. Our study demonstrates how joint inversion of multiple data aids model interpretation. The resulting resistivity models provide equally well-fitting alternatives to single-method evaluation, and additionally fit other geophysical method’s observations (i.e. gravity and seismic methods). The direct comparison of the impact of constraining MT inversion with either a fixed structural model or a coupled data inversion highlights how well the MT solution space may be confined. In our study, the fixed structural model constraint outperforms the joint MT-gravity data analysis.

Description: Many current research questions in Earth Sciences are related to understanding the complex geological processes that dictatethe location of resource formation. Multivariate and multi-disciplinary measurements across disparate spatial scales are common and generate databases that cross traditional geoscientific domains such as geophysics, geochemistry and geology. To cope with this mass of information, integrative data assessment approaches are essential for optimal information extraction from the available data, enabling more accurate prognoses of where to find previously undiscovered natural resources. This is especially true in the deep ocean, where data collection is inherently more difficult than on land. Here, we present an example from predicting the spatial distribution of seafloor massive sulfides (SMS) at the Trans-Atlantic Geotraverse (TAG) hydrothermal field using various sources of marine geophysical data, including high-resolution bathymetry and magnetics collected with an autonomous underwater vehicle (AUV), as well as conductivity data derived from Controlled-Source Electromagnetic (CSEM) measurements. Electrical conductivities are considered a direct SMS indicator as these exhibit a substantial conductivity variation to the surrounding host rock. Due to the size of the survey area, a spatial sampling of conductivity on a dense grid is not economical and would require many years of data acquisition. As a result, robust extrapolation of sparsely sampled conductivity data onto a regional scale seems efficient for predicting additional occurrences of SMS by integrating the acquired marine geophysical data into a Data Science framework. We show that this framework may improve current SMS predictions through associated prediction uncertainty, thereby detecting observational gaps and informing further sparse sampling of ground-truthing data (e.g. sampling or visual observations).

Description: Gas hydrate dynamics may impact the global carbon cycle and global warming. They may be used as a possible future energy source, but their dynamics may also influence slope stability. Therefore, their occurrence, formation, dissociation, and mobilization are of high interest. The quantification of gas hydrates in continental margins, either by drilling or geophysical methods, is the bases to understanding gas hydrate dynamics. To provide estimates of the gas hydrate saturation the common methodology reaches from the simple detection of gas hydrates by seismic imaging to more sophisticated approaches using the combination of geological, geochemical and geophysical methods. While most geophysical experiments use empirical relationships like Archie’s Law to derive saturations from remotely sensed data, a coupling of rock physics and geophysics by effective medium modeling offers new perspectives to directly invert for porosity, gas and gas hydrate saturations. We apply a joint elastic and electric approach by using a self-consistent approximation/differential effective medium model (SCA-DEM) on data from downhole P-wave velocity and induction sensors, recorded in a sedimentary setting at Formosa Ridge south-westoff Taiwan. In a first step, we construct a background model and derive porosity distributions from the data. Subsequently, we invert the complete borehole dataset for gas and gas hydrate saturations. A sensitivity analysis shows how the joint elastic andelectric approach is able to distinguish between gas and gas hydrate saturations and thereby overcomes the widely observed disagreement in saturation levels between seismic and electromagnetic methods. This approach lays the foundation to directly derive saturation levels from an existing joint geophysical electromagnetic and seismic dataset at Formosa Ridge.

Description: Groundwater aquifers are important for the freshwater supply all over the world, especially in dry regions. It occurs that the water bearing rock matrix extends offshore below the sea floor, and as a consequence fresh water is embedded within good conducting seawater-saturated sediments. Whether an aquifer is open to seawater intrusion or closed, depends on the local hydrogeological setting. Prior studies showed that for high demand on fresh water and high exploitation rates, it is necessary to understand the interaction between sea and fresh water to prevent deterioration of the aquifer. Several geophysical surveys have been carried out in the past to investigate a coastal aquifer in the Palmahim region of Israel, which serves as one of the main reservoirs of the national water supply system. Time domain marine LOTEM and DED data have thereby been recorded on similarprofiles. Both results show a resistor at an assumed aquifer depth of roughly 100 m with a comparable offshore extension of 3.5 km from the coastline. However, until now the LOTEM and DED data have only been interpreted separately using 1D inversion and extensive 2D forward modeling. This study presents the first joint 1D and 2D inverse modeling studies of marine LOTEM and DED techniques using synthetic and field data. The synthetic results indicate large benefits of using a joint inversion of both appliedsurvey techniques. However, a joint inversion of the field data is still in progress. Yet, a 2D inversion of the DED data is promising and indicates a brackish transition zone at the expected lateral aquifer boundary. This finding seems consistent with prior studies and suggests an open aquifer scenario with seawater intrusion. This outcome is essential for the groundwater management and supply in Israel.

Description: Volcanic island sector-collapses have produced some of the most voluminous mass movements on Earth and have the potential to trigger devastating tsunamis. In the marine environment, volcanic landslide deposits often consist of a mixture of volcanic material and incorporated seafloor sediments. The interaction of the initial volcanic failure and the seafloor is highly complex and has an impact on both the total landslide deposit volume and its emplacement velocity, which are important parameters during tsunami generation and need to be correctly attributed during numerical landslide-tsunami simulations. Here, we present a 2D seismic analysis of two previously unknown volcanic landslide deposits north-west of the island of Sakar (Papua New Guinea) in the Bismarck Sea. The younger deposit directly overlies the older one and both are separated by a package of well-stratified sediment. Despite both originating from the same source, with the same broad failure direction, and having similar deposit volumes (~15.5-26 km3), the interaction of these landslides with the seafloor is markedly different. High-resolution seismic reflection data show that the lower deposit comprises a proximal, chaotic, volcanic debris avalanche component and a distal, frontally confined seafloor-sediment failure component. Deformation of this sediment unit was probably caused by interaction of the debris avalanche component with the substrata. The unit shows various compressional structures, including thrusting and folding, over a downslope distance of more than 20 km, generating a shortening by 〉27 % in the deposit’s toe. The volume of the deformed sediments is almost the same as the driving debris avalanche deposit. In contrast, the younger landslide deposit does not show evidence for similar seafloor sediment incorporation and is a relatively simpler block-rich volcanic debris avalanche deposit. Our observations show that the nature of the slide plane, i.e., the geological characteristics of the underlying material, control the amount ofseafloor incorporation and secondary seafloor failures far more than the nature of the original slide material or other characteristics of the source region. Our results indicate that estimating the volume of volcanic sector collapses based solely on the surface morphology and extent of their deposits may overestimate the primary volcanic component, which is much more important for tsunami generation than secondary sediment failure, by a factor of 2

Description: A new mixed turbidite-contourite system is described in the northern Campos Basin, southeastern Brazilian margin. This system is developed in a middle slope setting and was formed through non-synchronous interaction between the turbidity current and a contour current in the same stratigraphic interval (Miocene). Different depositional cycles were accounted based on their diagnostic seismic features. Seismic attributes, seismic facies, and isochron maps were used to identify alternating cycles of downslope and alongslope processes in the study area, along with the intermediate stage with features from both processes (mixed system). The depositional processes resulted from alongslope current activity can be distinguished from the downslope current activity, based on the acoustic characteristics (root-mean-square (RMS) amplitude), internal architecture, and external geometry pattern. While alongslope currents deposits consist of mainly low RMS amplitude values clinoforms with an alongslope trend; the downslope gravity deposits present high-amplitude or chaotic seismic facies, usually higher values of RMS amplitude, channel or channel-lobe features, erosive surfaces, and a basinward depositional trend. In this study, five seismic units are described and later associated with their dominant type of current. Based on the main depositional diagnostic features, it was possible to determine which were the dominant processes that controlled the sedimentation by indicating periods where the margin was mostly submitted to sediment transfer from continent to the basin and periods wherethe oceanic currents prevailed by redistributing sediments along the isobaths and replacing the axis of downslope transfer conduits. Important information on the paleocurrents' direction was also made based on the final deposits display (e.g. terraces, sediment waves, paleochannels), a northward-flowing bottom current was assumed. Research on alternating dominant processes and mixed depositional systems may provide a better understanding of deep-water depositional processes. Because these processes do not always fit previous depositional models that are mainly described for synchronous systems, new insights on cyclic non-synchronous mixed systems can improve our understanding of how mixed systems are organized through time and space. Setting new models on cyclic deposits and intermediate stages can have a future economic impact on potential hydrocarbon reservoir architecture.

Description: The Alpine orogen and the Apennine system are part of the complex tectonic setting in the Mediterranean Sea caused by the convergence between Africa and Eurasia. Between 30 Ma and 15 Ma the Calabrian subduction retreated in a southeast direction pulling Corsica and Sardinia away from the Eurasian landmass. In this extensional setting, the Ligurian Sea was formed as a back-arc basin. The rifting jumped 15 Ma ago in the Tyrrhenian Sea leaving Corsica and Sardinia in a stable position relative to Eurasia.Within the framework of the AlpArray research initiative a long-term seismological experiment was conducted in the Ligurian Sea to investigatethe lithospheric structure and the seismicity in the Ligurian basin. The passive seismic network consisted of 29 broad-band ocean bottom stations from Germany and France. It was in operation between June 2017 and February 2018.Two seismicity clusters occurred in the centre of the Ligurian Basin. The 18 earthquakes are located in the lower crust and in the upper-most mantle at depths between 10 km and 16 km. Re-location was performed only using picks from the OBS in the centre of the Ligurian Sea to avoidartifacts from the complex 3D velocity structure of the basin. Moho-refractions Pn and Sn have apparent velocities of 8.2 km/s and 4.7 km/s. The low Vp-Vs-ratio of 1.72 indicates a more brittle behaviour of the mantle material. Fault plane solutions were determined for four events using also the data of land stations in southern France, Corsica, Sardinia and northern Italy. The focal mechanisms are thrust faulting. Fault planes strike in a NE-SW direction, coinciding with the alignment of the events and the direction of the basin axis. We interprete the two earthquake clusters related to the inversion of the Ligurian Basin where the basin's centre is under compression and stresses are taken up by reactivated faults in the crust and uppermost mantle. The compressional forces could be caused by the convergence of Africa and Europe. In general, observations of earthquakes in continental mantle lithosphere are rare and they reveal on the one hand a strengthening of the crust and uppermost mantle during riftingand on the other hand they support the interpretation that rifting failed in the northern Ligurian Basin.

Description: Driven bysignificant economic benefits, the hydrocarbon industry developed sophisticated methods for the integration of geophysical and geochemical measurements with direct core observations. However, these techniques were developed primarily for sedimentary settings and have been applied only seldom in metamorphic settings. One outstanding example for comprehensive geophysical and borehole data integration is the COSC-1 borehole in the central Scandinavian Caledonides. It was drilled in 2014 and resulted in an extensive dataset to shed light on deformation during continental collision. Our study combines data from downhole logging and zero-offset vertical seismic profiling at COSC-1, with 2D and 3D seismic measurements to provide constraints on the spatial lithological and textural configuration of the Seve Nappe Complex. We show that there are powerful tools to distinguish between mafic and felsic lithologies in log-core correlation but that metamorphic settings bear special challenges for core-log-seismic integration. In contrast to sedimentary basins, reflections in the Seve Nappe Complex are not as distinct but we can link several of them to magmatic intrusions, which have been metamorphically overprinted. Their setting indicates that the Seve Nappe Complex consists of the remnants of a volcanic continental margin. It appears that in spite of the metamorphic overprint around 417+/-9 Ma, the original configuration of the volcanic passive margin is partly preserved in the Seve Nappe Complex and it thus outlasted continent-continent collision including the nappe emplacement. Integration of borehole and three-dimensional geophysical data reveals lithological changes that can then be extrapolated in three dimensions to arrive at a better understanding of the compositionand geometry at mid-crustal levels. Furthermore, our results suggest that mid-crustal reflectivity at COSC-1 is primarily a function of pre-orogenic lithological variations which has to be considered when deciphering mountain building processes.

Description: The Cape Verde archipelago is a group of Ocean Islands in the Central Atlantic that forms two chains of islands trending Northwest and Southwest. Several of the islands are considered to be volcanically active, with frequent eruptions on Fogo. We examine the mineral chemistry and thermobarometry of the southern islands; Santiago, Fogo and Brava together with the Cadamosto Seamount. Our objective is to explore the magmatic storage system and implications for volcanic eruptions and associated hazards at Cape Verde. The volcanic rocks at Cape Verde are alkaline and dominantly mafic, whereas the island of Brava and the Cadamosto Seamount are unusually felsic. Clinopyroxene compositions range from 60 to 90 Mg# at Santiago and Fogo. In contrast, at Brava and the Cadamosto Seamount the clinopyroxene compositions are 5 to 75 Mg#. Mineral chemistry and zonation records fractional crystallization, recharge, aggregation of crystals, magma mixing and variations in thermal conditions of the magma at temperatures from 925 to 1250C. Magma storage depths at Santiago, Fogo, Brava and the Cadamosto Seamount are between 12 and 40 km, forming deep sub-Moho magma storage zones. Transient magma storage in the crust is suggested by fluid inclusion re-equilibration and pre-eruption seismicity. A global compilation of magma storage at Ocean Islands suggests deep magma storage is a common feature and volcanic eruptions are often associated with rapid magma ascent through the crust. Shallow magma storage is more variable and likely reflects local variations in crustal structure, sediment supply and tectonics. Petrological constraints on the magma plumbing system at Cape Verde and elsewhere are vital to integrate with deformation models and seismicity in order to improve understanding and mitigation of the volcanic hazards.

Description: 02.08.-08.08.2021

Description: Seafloor geodesy experiments have been expanding considerably in recent years. More and more research teamsaround the globe are conducting projects to monitor the tectonic or volcanic deformation of the seafloor. Theseexperiments are commonly based on limited-duration experiments, but increasingly, permanent observatories arealso being installed. This dynamic development is very encouraging for the establishment of a strong community which arguably willlead to the emergence of a worldwide scientific and technical synergy. However, data andknowledge transferbetween the different groups working on similar topics are still limited at the present time. This can be partlyexplained by the fact that the instruments, infrastructure, and processing software developed are custom-made andthus various file formats are used, although the fundamental observables are most of the time identical. One wayto overcome this limitation is to set up exchange standards in the form of standardized file formats. These fileswould gather and store all the physical quantities observed and will prove useful for the processing simplificationand, in the end, the extraction of the geodetic signal sought. Furthermore, uniformized formats would allow muchmore easily the comparison of software and processing methods between research groups, whether during tests oroperational measurement campaigns. Standardized data will eventually provide a base for the activities of potentialfuture national or international observation services. They would also make it possible to envisage the datadissemination similar to geodetic data recorded on land.

Description: Various electromagnetic (EM) measuring techniques were developed to fulfil the requirements in diverse earth or resources explorations, such as the long-offset transient electromagnetic (LOTEM) and the semi-airborne EM methods. The novel semi-airborne frequency-domain electromagnetic system takes advantages of both ground and airborne techniques by combining ground-based high power sources with large scale and spatially dense covered data. However, its signal-to-noise ratio is still smaller in comparison with the ground-based method like LOTEM due to the limited stacking time. From the perspective of inversion, the data of different EM methods have distinct resolutions towards the subsurface resistivity structures and therefore they can provide complementary earth information. However, these distinct resolutions could also lead to different inversion results if each dataset is inverted individually, which may introduce confusions to the following interpretations. To reduce the ambiguities and parameter uncertainties, joint inversion algorithms are developed to couple spatially dense sampled semi-airborne data and horizontal electric fields (Ex) measured using LOTEM. Nevertheless, the 1D joint inversion faces convergence problems due to 2D effects in the field data. The synthetic modelling suggests that the 2D effects in different datasets lead to distinct artificial structures in the 1D inversion, which makes the 1D joint inversion unfeasible. Therefore, a 2D joint inversion algorithm was further developed for the frequency-domain semi-airborne EM data and the LOTEM transient electric fields. With its application, the newly developed 2D joint inversion of the semi-airborne and LOTEM Ex field data acquired in eastern Thuringia,Germany, converged successfully and a 2D conductivity model could be derived for the survey area. In the consequent 2D synthetic modelling studies, it is demonstrated that part of the discrepancies between the individual inversion result of each field dataset can be explained by the resolution differences leaded by the different observed quantities and by the measurement configurations, and the 2D joint inversion result of field data is validated to be one effective equivalent model.

Description: Hydrocarbon gases are actively seeping from pockmarks in the eastern part of the Vestnesa Ridge, western-Svalbard Margin. One of these is Lunde pockmark which is characterized by a seismic chimney below. Such seismic anomalies are widely believed to represent fluid migration pathways. However, their detailed structure and the physical properties of such structures is poorly understood and might be highly variable. Tomographic seismic velocity analysis can resolve the inner structure of the chimney beneath the Lunde pockmark. The aim is to understand the distribution of gas hydrate, free gas and carbonates within the gas chimney. Here, we present first results of our detailed 3D seismic travel time tomography using newly acquired high-resolution ocean bottom seismometer data guided by high-resolution 3D multi-channel seismic data. These models were generated with the Jive3D software. Our initial results show the variability of the seismic velocity structure beneath the Lunde pockmark. Our analysis, combined with earlier datasets and results shows that fluid pathways through the gas hydrate stability zone are anything but simple and highlights the importance of understanding the evolution of methane seepage pathways through time.

Description: Die Erde erwärmt sich aufgrund des anthropogen verursachten Anstieges von Treibhausgasen. Im Weltrisikobericht des Weltwirtschaftsforums, der alljährlich analysiert, mit welchen Gefahren die Welt in den kommenden Jahren konfrontiert sein wird und wo der dringendste Handlungsbedarf besteht, führt der Klimawandel die Liste der größten Risiken an. Die Folgen des Klimawandels werden besonders im Ozean offensichtlich, der wiederum eine Schlüsselrolle im Klimasystem spielt.Was wissen wir eigentlich über den Klimawandel? Was sind seine Ursachen und welche Folgen hat er für den Ozean? Welche Handlungsoptionen bietet der Ozean um dem Klimawandel zu begegnen?Im Vortrag werden der aktuelle Wissensstand zur Rolle des Ozeans im Klimawandel sowie Chancen und Risiken möglicher Handlungsoptionen präsentiert

Description: Focused fluid flow shapes the evolution of marine sedimentary basins by transferring fluids and pressure across geological formations. Vertical fluid conduits may form where localised overpressure breaches a cap rock (permeability barrier) and thereby transports overpressured fluids towards shallower reservoirs or the surface. Here, we study field outcrops of an Eocene fluid flow system at Pobiti Kamani and Beloslav Quarry (~15 km West of Varna, Bulgaria), where large carbonate-cemented conduits formed in highly permeable, unconsolidated, marine sands of the northern Tethys Margin. Using an uncrewed aerial vehicle with an RGB sensor camera we produced ortho-rectified image mosaics, digital elevation models, and point clouds of the two km-scale outcrop areas. Based on these data, geological field observations, and petrological analysis of rock/core samples, we mapped and analysed fractures and vertical fluid conduits with centimetre accuracy. Our results show that both outcrops comprise several hundred carbonate-cemented fluid conduits (pipes), oriented perpendicular to bedding, and at least seven bedding-parallel carbonate interbeds which differ from the hosting sand formation only by their increased amount of cementation. From these observations, we conclude that carbonate precipitation likely initiated around areas of focused fluid flow, where methane entered the formation from the underlying fractured subsurface. These first carbonates formed the outer walls of the pipes and continued to grow inward leading to self-sustaining and self-reinforcing focused fluid flow. Our results, supported by literature-based carbon and oxygen isotope analyses of the carbonates, indicate that ambient seawater and advected fresh/brackish water were involved in the carbonate precipitation by microbial methane oxidation. We propose that similar structures may also form in modern settings where focused fluid flow advects fluids into overlying sand-dominated formations, which has wide implications for our understanding of how focusing of fluids works in sedimentary basins with broad consequences for the migration of water, oil, and gas

Description: Strong anisotropy of seismic velocity in the Earth crust poses serious challenges for seismic imaging. Where in situ seismic properties are not available the anisotropy can be determined from independent surface and borehole seismic profiles. This is well established for dense, long-offset reflection seismic data. However, it is unknown how applicable this approach is for sparse seismic reflection data with low fold and short offsets. Here, we show that anisotropy parameters can be determined from a sparse 3D data set at the COSC-1 borehole site in the Swedish Caledonides and that the results agree well with the seismic anisotropic parameters determined on core samples from laboratory measurements. Applying these anisotropy parameters during 3D seismic processing significantly improves the seismic imaging of the high amplitude reflections especially in the lower part of the borehole. Strong reflectors in the resulting seismic data align well with the borehole-derived lithology. Our results aid the interpretation and extrapolation of the seismic stratigraphy of the Lower Seve Nappe.

Description: Kolumbo represents one of the most hazardous, currently active, volcanoes in the eastern Mediterranean. Its last eruption in 1650 AD was associated with a vast explosion, causing a tsunami of regionally devastating impact. The eruption was also associated with the voluminous and rapid release of toxic gases asphyxiating humans and animals on the nearby Islands. Earthquake records from the recent decades document on-going unrest beneath the volcano. Several active hydrothermal vent sites and bacterial mats are present at the crater floor, concentrated near the northern crater wall. The vents emit mainly CO2, leading to the accumulation of acidic waters in the crater. Accordingly, one of the main volcanic hazards associated with Kolumbo is that rapid overturning of waters in the crater may release harmful amounts of toxic gases. Monitoring the hydrothermal processes inside the Kolumbo crater will provide an important contribution to the understanding and evaluation of this and other volcanic hazards.In October 2019, we deployed an ocean bottom seismometer and hydrophone (OBS/H) inside the Kolumbo crater. During the four days of passive recording we identified about 100 so-called short duration seismic events, which were only present on the seismometer channels, but absent on the hydrophone channels. The events have durations of less than one second with dominant frequencies between 5 to 30 Hz. Most of the events represent well-polarized seismic phases, which enables us to determine their azimuth incidence angles at the OBS/H. The azimuth angles of all events in the largest cluster coincide with the azimuth angle between the station and the field of hydrothermal vents and bacterial mats inside the crater. This coincidence suggests that the origin of the short duration events is associated with the sub-seafloor migration of fluids or the fluid discharge process at the crater floor. In fact, short-duration events of similar characteristics, recorded by OBS/H, were previously attributed to sub-seafloor fluid migration and the discharge of fluidsat the seafloor. Our analyses indicate that seismic monitoring of submarine volcanoes should include the detection and analysis of short duration events, which may act as a tool to characterize volcanogenic geohazard monitoring.

Description: The goal of core-log-seismic integration is to glean new scientific understanding from diverse datasets that span the millimeter to kilometer scale. Germany plays an important role in international scientific drilling, with major core curation and data management centres, as well as broad expertise in seismicdata acquisition, borehole logging and sediment core investigations. Springboarding from this solid foundation, we propose to establish a virtual Core-Log-Seismic Integration Research Centre to act as a nucleus for conceiving and running research projectsthat harvest the untapped potential of hundreds of scientific boreholes. We envisage that scientists from Germany, in collaboration with key international partners, should work closely together and provide the critical mass and long-term expertise to sustain the research centre. We see this an ideal way to foster collaboration within Germany and globally.In this presentation we will describe this new initiative and provide some examples of on-going and developing research projects that are underpinned by core-log-seismic integration methods. The examples will include investigations into submarine landslide processes (offshore New Zealand), gas hydrate formation (offshore Taiwan) and continental collision (onshore Sweden).

Description: Metamorphic testing seeks to verify software in the absence of test oracles. Our application domain is ocean system modeling, where test oracles rarely exist, but where symmetries of the simulated physical systems are known. The input data set is large owing to the requirements of the application domain.This paper presents work in progress for the automated generation of metamorphic test scenarios using machine learning. We extended our previously proposed method [1] to identify metamorphic relations with reduced computational complexity. Initially, we represent metamorphic relations as identity maps. We construct a cost function that minimizes for identifying a metamorphic relation orthogonal to previously found metamorphic relations and penalize for the identity map. A machine learning algorithm is used to identify all possible metamorphic relations minimizing the defined cost function. We propose applying dimensionality reduction techniques to identify attributes in the input which have high variance among the identified metamorphic relations. We apply mutation on these selected attributes to identify distinct metamorphic relations with reduced computational complexity. For experimental evaluation, we subject the two implementations of an ocean-modeling application to the proposed method to present the use of metamorphic relations to test the two implementations of this application.

Description: A Pyhton-based toolbox to remap daily runoff fields of the JRA55-do reanalysis (Tsujino et al., 2018, https://doi.org/10.1016/j.ocemod.2018.07.002) onto any ocean model grid. Runoff from the original global JRA grid is collected and redistributed to a given model coastline. A particular feature is the optional treatment of river mouths: runoff from grid nodes, which is of exceptionally large magnitude after the basic remapping, can be radially spread to ocean nodes farther offshore. The scripts were tested successfully for NEMO ocean model configurations of various resolution (global grids ORCA025 and ORC05 as well as regional nests VIKING10, ORION10, VIKING20X and INALT20X) at GEOMAR, Kiel (see Biastoch et al., 2021, https://doi.org/10.5194/os-2021-37 for an application). General instructions are provided for how to process the original JRA runoff files and also for the optional river mouth treatment. The technique is illustrated by examples of the fragmented coast of Greenland and the Amazon river mouth. While the code is versatile, examples are given for an application with the NEMO ocean model.

Description: Ulva-like green algae are notoriously difficult to distinguish because of their great morphological variability and/or similarity, and DNA barcoding approaches are currently indispensable for their identification. However, such approaches often fail if rare or inapparent species are to be detected in large mixed green algal stands. We therefore developed a detection method based on next generation DNA sequencing, suitable for analysis of DNA traces in conserved water samples. A primer pair was developed that allows for amplification of a 475 bp long section within the tufA marker gene. The primers are relatively group specific, as 79.6 % of all reads obtained after quality filtering represented Ulvophyceae. The relatively short target amplicon still allows for good differentiation of Ulvales and Ulothrichales at the species level. Using a database containing tufA sequences of 879 species – thereof 281 Ulvophyceae – we detected predominantly species that were previously observed in our study area in Northern Germany. However, the number of species detected in single sites was generally higher than in earlier barcoding studies, which may be due to drifting genetic traces: Samples collected offshore appeared influenced by Ulvophyceae present within a radius of up to about 1 km in winter and less than 100 m in summer. Nonetheless, this new approach can be used to detect rare species: In one site an undescribed Blidingia species not yet known from our study area was repeatedly detected. Based on these findings the species was discovered and its identity was confirmed by traditional tufA barcoding.

Description: This deliverable maps the locations and properties of sustained biological observing networks through Europe including identifying coordinating groups and data aggregators. Data come from a global survey of networks, supplemented by an analysis of sustained observations in OBIS (that receives all biological data from EMODNet).

Description: Modern digital scientific workflows - often implying Big Data challenges - require data infrastructures and innovative data science methods across disciplines and technologies. Diverse activities within and outside HGF deal with these challenges, on all levels. The series of Data Science Symposia fosters knowledge exchange and collaboration in the Earth and Environment research community. We invited contributions to the overarching topics of data management, data science and data infrastructures. The series of Data Science Symposia is a joint initiative by the three Helmholtz Centers HZG, AWI and GEOMAR Organization: Hela Mehrtens and Daniela Henkel (GEOMAR)

Description: Monitoring of geological CO2 storage is crucial for large-scale injection to gain public acceptance. Monitoring plans for large-scale operations need to include both the injection and post-injection phases to assure CO2 is safely stored permanently. The SENSE project aims to develop reliable, continuous, and cost-efficient monitoring based on ground movement detection combined with geomechanical modeling and inversion, utilizing new technology developments, data processing optimization, and interpretation algorithms. The proposed research activities include: • demonstration of continuous monitoring of surface deformation and subsurface pressure distribution using satellite data, water pressure sensors and fiber optics; • quantitative characterization of critical geomechanical and hydraulic parameters and automatization routine for data processing and interpretation; • optimization of sampling arrays in order to offer storage site operators a cost-effective monitoring option as part of an effective site assurance program. The SENSE project brings together experts from 14 international institutions of nine different countries to solve challenges in CO2 storage site monitoring and to provide solutions for safe and successful injection and post-closure phases of site operation. The project is organized in five Work Packages (WPs); WP1: Quantification of ground movement, WP2: Geomechanical modeling and rock strain assessment, WP3: History matching inversion and coupled flow-mechanics, WP4: Integration of results for cost-effective monitoring and WP5: Project management. The ultimate goal of SENSE is to offer storage site operators a cost-effective monitoring option that can form part of an effective site assurance/monitoring program and feed into workflows for an early alert system to detect unexpected changes in the subsurface. The SENSE project has four demonstration sites for monitoring technologies and developing concepts and procedures. These sites are both onshore and offshore. The onshore sites include In Salah (Algeria) and Hotfield Moors (UK). For these sites, the project will use satellite data to explore the response of the surface to pressure changes in the subsurface. Algorithms for automatic satellite data processing to facilitate quick access to ground elevation data for site operators are under development at the British Geological Survey (BGS) and Norwegian Geotechnical Institute (NGI). The offshore sites include Bay of Mecklenburg (Germany) and the Gulf of Mexico (USA). In addition, the SENSE partners have requested access to data from the Troll Gas Field, the North Sea, to study its subsidence due to production-related pressure reduction. The Troll Gas Field is located next to the storage site considered for the Norwegian Long Ship project, and its data will provide a good understanding of the geomechanics of the area. In this paper, we present the work on the In Salah and the Bay of Mecklenburg sites. New InSAR data from the In Salah are used to evaluate the ground movement during the post-injection period and thus to assess the behaviour of the storage site after completion of the injection phase. Bay of Mecklenburg is an offshore site for field experiment to inject a gas underground, build-up pressure, uplift the seafloor and measure the resulted uplift. The first field campaign at the Bay of Mecklenburg was completed in late 2019. It provided both gravity cores from the seabed and geophysical data acquisition for characterizing the shallow subsurface layers. The gravity cores were characterized for physical and mechanical properties. The material properties were used for simulating injection and response of the seafloor to induced pressure. Geomechanical 2D and 3D simulations show that the reservoir may sustain very low overpressure before it fails. Hence, this magnitude of overpressure may create a seafloor uplift of about a few millimeters to a couple of centimeters. The monitoring techniques are therefore being designed to capture uplift in this order of magnitude during the injection operation.

Description: Ulva-like green algae are notoriously difficult to distinguish due to their morphological variability and/or similarity. DNA barcoding approaches are therefore currently essential for their reliable identification. However, such approaches often fail when rare or inconspicuous species are to be detected in large mixed populations of Ulva species, for example, at early stages following the introduction of species into new habitats. We therefore developed a detection method based on next-generation DNA sequencing. The approach is suitable for the analysis of DNA traces in preserved water samples or in particles enriched by filtration from such samples. A new pair of primers was designed to amplify a 475 bp segment within the tufA marker gene. The primers were relatively group specific. 68.5% of all reads obtained after quality filtering represented the genus Ulva, 11.1% other Ulvophyceae, and only 20% other Chlorophyta, despite their relatively higher abundance in phytoplankton. The relatively short target amplicon still allows good differentiation of Ulvales and Ulothrichales at the species level. Using a database containing tufA sequences of 879 species - 281 of which were Ulvophyceae and 35 Ulva - we were able to detect mostly Ulvophyceae that had been previously detected in our study area in northern Germany using Sanger sequencing. However, the number of species detected at individual sites was generally higher than in previous studies, which could be due to drifting DNA: Analysis of samples collected at different distances from shore suggests that a sample collected at a given site may be influenced by Ulvophyceae within a radius of up to about 1 km in winter. In summer, this radius is reduced to less than 100 m, possibly due to the less frequent occurrence of strong wind events. Nonetheless, rare species may be detected with this new approach: At one site, an undescribed Blidingia species that was not previously known from our study area was repeatedly detected. Based on these findings, the species was searched for and found, and its identity confirmed by traditional tufA barcoding.

Description: This deliverable reports about the successful completion of three group discussions on marine carbon dioxide removal (CDR) with laypersons in Germany. The 2-hour group discussions were held online. 5 participants discussed these three topics: (1) the environmental state of the oceans, (2) four selected marine CDR approaches, and (3) responsible research and innovation. The four approaches were ocean fertilization, ocean alkalinization via ocean liming and electrochemical weathering in desalination plants, artificial upwelling, and blue carbon management via kelp forests, mangroves and seagrass meadows.

Description: Carbonate lithologies host considerable quantities of the Earth’s freshwater resources and partially supply a significant amount of the global population with drinkable water. Although they comprise substantial amounts of the coastlines, it is not known if these carbonate lithologies can sustain freshened groundwater offshore, and if this can help meet future water demands in coastal regions. To date, predicting volumes of freshened groundwater within marine carbonates has been challenging. Here, we integrate controlled source electromagnetic profiles with seismic reflection and core log data to derive a lithological model for the eastern carbonate margin of the Maltese Islands, one of the most water-starved countries in the world. Electrical resistivity models are used to guide lithological inference where seismic data provide limited information due to the superimposed seafloor multiple. We show that resistivity values within the Upper Coralline and Globigerina Limestone formations exceed the measured resistivity of seawater-saturated core log samples by at least a factor of four. This could be indicative of offshore freshened groundwater that occupies the pore space of the low permeability limestone along the eastern Maltese shelf. To validate this observation without further ground-truthing data, we use extensive forward modelling to show that a similar resistivity footprint can be achieved by localized interbedded low-porosity or highly cemented units. However, the spatial extent of such units across the entire eastern Maltese margin is geologically improbable. This points to the occurrence of offshore freshened groundwater that was likely emplaced during the last sea-level lowstand.

Description: This deliverable reports about the successful completion of three group discussions on marine carbon dioxide removal (CDR) with laypersons in Norway. The 2-hour group discussions were held online. In three groups, and a pilot group, between 2 and 7 participants discussed these three topics: (1) the environmental state of the oceans, (2) four selected marine CDR approaches, and (3) responsible research and innovation. The four approaches were ocean fertilization, ocean alkalinization via ocean liming and electrochemical weathering in desalination plants, artificial upwelling, and blue carbon management via kelp forests, mangroves and seagrass meadows.

Description: FS METEOR Expedition M175 „Transformers II“, 7. - 13. Juni 2021

Description: Seafloor massive sulfides (SMS) are regarded as a potential future resource to satisfy the growing global demand of strategic metals. Aside from mining and retrieving profitable amounts of massive sulfides from the seafloor, the present challenge is to detect and delineate significant SMS accumulations, which are generally located near mid-ocean ridges and along submarine volcanic arc and backarc spreading centers.In the past years we have used the marine transient electromagnetic induction system MARTEMIS, a coincident-loop TEM system developed at GEOMAR (Kiel, Germany), in various marine geological settings for the detection and characterization of SMS in the shallow seafloor down to a depth of ~30m. The system was also used in combination with remote EM receivers (Coil2Dipole experiment) to allow for investigations of conductive structures,which are covered by up to ~100m of sediments.During two research cruises (2015: POS483, 2017: POS509), several types of EM experiments were carried out at the Palinuro Seamount located about 141km to the SSE of Naples (Italy) in the Tyrrhenian Sea. At this hydrothermally practically inactive site, previous investigations had confirmed the occurrence of SMS by drilling down a depth of 5m, the maximum depth reached by the drill (BGS Rockdrill I). For all EM experiments we used the marine transient induction system (MARTEMIS) -a mobile marine coil system -as source. For TEM experiments a coincident loop receiver integrated into the MARTEMIS system was used to investigate the shallow conductivity structure of the seafloor down to a depth of about 30m. In the TEM experiments we were able to show that the lateral extent of the SMS body is larger than previously known from drilling. In a second set of experiments, which we have named "Coil2Dipole", we used remote OBEM (ocean bottom EM) receivers to measure theelectrical fields excited by the MARTEMIS coil source. In this experiment, OBEM receivers were able to detect the transmitted signal up to distances of about 250m, which yields an increased penetration depth of about 120m as compared to the TEM experiment. A first evaluation of the OBEM data indicates a conductor to the SW of the known mineralization at greater depth, which we interpret as the mineralized feeder channels to the known SMS site.

Description: FS METEOR Expedition M175 „Transformers II“, 21. - 28. Juni 2021

Description: Alkor Fahrt AL557, Cuxhaven-Cuxhaven, 4.6.2021-23.6.2021: Zweiter Wochenbericht (13.6.2021-22.6.2021)

Description: Subsea carbon dioxide leakages from geological storage complexes and transmission lines may pose a threat to the marine ecosystem in their vicinity. For high leakage flow rates (100 kg/s), buoyant dynamic plumes will form and, in shallow water depths (100-300 m) such as in continental shelves, they may reach the water surface thereby releasing gases to the atmosphere. Here, we present simulations of subsea releases of CO2 at varying scales, such as seeps, point source plumes and line source plumes, and we discuss their behaviors. The simulated release conditions and water depths are representative of potential storage area on the Norwegian Continental Shelf. Simulations are performed with the TAMOC model, a multiphase-integral plume modeling suite developed and validated for subsea gas and oil releases.

Description: Article 4 of the Paris Agreement calls for a “balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century”. It is not made explicit if this balance should be achieved for each of the greenhouse gases (GHGs) individually or if some sum of all GHGs is supposed to become net-zero. This confusion translated into several declared climate targets, that range from carbon-neutral, over GHG-neutral to climate-neutral, and sometimes use these terms interchangingly. However, these targets imply different trajectories in terms of single GHG emissions and result in vastly different temperature trajectories. Here, we show the implications of this confusion concerning declared climate target metrics, using the most commonly used metric of CO2-equivalent emissions. The same trajectory of net-zero-2050 CO2-equivalent emissions, shows vast differences in short term and long-term temperature and carbon cycle responses, depending on the distribution of CO2-equivalent emissions across the different GHGs. We emphasize that achieving net zero CO2 emissions remains a necessary precondition for long-term temperature stabilization. We also show that methane emissions reduction can have large short term benefits, as it would strongly reduce the short term temperature and thereby increase the natural carbon uptake. Going forward we recommend to aim for more transparency in declared climate goals and suggest aiming to achieve net zero anthropogenic emissions for all GHGs individually.

Description: Submarine landslides are widespread phenomena on continental slopes and act as prime sediment transport processes between shallow and deep marine regions. In addition, they pose significant risk to coastal communities worldwide. Within this study, we focus on the Ana Slide, a relatively small landslide with areal extent of 4.7 km2located at water depth between 635 –905 m on the eastern slopes of the Eivissa Channel, western Mediterranean. Predominant sediment types are high-water content, carbonate-dominated hemipelagic deposits susceptible to high pore pressures and liquefaction. Available data include very-high resolution bathymetric and a 3D seismic dataset completely covering the landslide.The Ana Slide is characterised by three landslide domains: the 1) evacuational or headwall domain, 2) translational domain, and 3) accumulational or toe domain. While the headwall domain demonstrates classic features of material evacuation and poses as the exclusive source of material within the landslide process, the translational domain documents extensive in-situ remnant blocks which were unaffected during failure. Instead, landslide material from the evacuational domain moved up and over the translational domain. The toe domain exhibits extensive chaotic seismicfacies with compressional ridges throughout the deposit and imprinted onto the seafloor. Even though extensive chaotic seismic facies characterise the toe domain, its volume differs significantly from the volume of the evacuated material from the headwall domain. Thus, we conclude that the chaotic seismic facies does not represent landslide material. Instead, the in-situ sediment underwent a range of soft-sediment deformation processes. We propose two mechanisms responsible for this deformation: loading-and shearing-induced soft-sediment deformation resulting from rapid deposition of overburden material. Under consideration of the likely elevated pore pressure and liquefaction potential of deposits, these mechanisms lead to the destruction and disturbanceof internal reflections.Our analysis demonstrates the difficulties in distinguishing between actually failed landslide material and deformed but not translated sediment, which may well lead to erroneous landslide volume estimations. Our new model of the evolutionary development of the Ana Slide may well hold for many other submarine landslides globally, the volumes of which could be significantly overestimated.

Description: Since the last glaciation the Canadian Arctic Beaufort Shelf is subjected to marine transgression. From subaerial mean annual temperatures during terrestrial exposure of ≤ -20°C, thermal conditions changed up to present submarine bottom water temperatures near -1°C. While conditions during the Pliocene favoured extensive formation of permafrost and gas hydrates, present occurrences are exposed to degradation due to the warmer climate. Today, submerged offshore permafrost is still responding to this thermal change. Ongoing degradation creates the potential of methane release of previously trapped biogenic gas within the relic permafrost and from gas hydrate dissociation. The mobilisation of methane and its possible release to the atmosphere plays a significant role in climate change. Yet, both the extent of permafrost and underlying gas hydrates is still poorly known. Here, we present seismic indicators for offshore permafrost and gas hydrates in 2D multichannel reflection seismic data acquired in the Canadian Beaufort Sea. Seismic lines that run from the shallow shelf towards deeper water show layer-crossing reflections that become gradually shallower towards the north-west into deeper water. These reflections show an amplitude-varying characteristic and are phase-reversed. We first use shot gathers from a synthetic model based on the field seismic acquisition characteristics and borehole geophysical data to verify our general ability to detect permafrost-and gas hydrate-related reflections. The synthetic data were processed using the same data processing applied to the field data and reveal clear top and base of permafrost and gas hydrate reflections. With this encouraging result, we can exclude any potentially misleading processing artefacts in the field seismic data. We interpret the amplitude-varying, phase-reversed and layer-crossing reflections seen in the field data as seismic indicators for the base of permafrost and base of gas hydrates. In contrast to the synthetic data, top of permafrost and top of gas hydrates are not clearly identified in the field data. However, additional seismic indicators support the interpretation of the presence of permafrost including attenuation of acoustic penetration and velocity pull-up effects at presumably horizontal strata. Furthermore, strong amplitude variations beneath the current base of gas hydrates and bright spots indicate trapped free gas accumulations from possible previously dissociated gas hydrates.

Description: The Ligurian Basin is located north-west of Corsica at the transition from the western Alpine orogen to the Apennine system. The Back-arc basin was generated by the southeast retreat of the Apennines-Calabrian subduction zone. The opening took place from late Oligocene to Miocene. While the extension led to extreme continental thinning little is known about the style of back-arc rifting. Today, seismicity indicates the closure of this back-arc basin. In the basin, earthquake clusters occur in the lower crust and uppermost mantle and are related to re-activated, inverted, normal faults created during rifting.To shed light on the present day crustal and lithospheric architecture of the Ligurian Basin, active seismic data have been recorded on short period ocean bottom seismometers in the framework of SPP2017 4D-MB, the German component of AlpArray. An amphibious refraction seismic profile was shot across the Ligurian Basin in an E-W direction from the Gulf of Lion to Corsica. The profile comprises 35 OBS and three land stations at Corsica to give a complete image of the continental thinning including the necking zone.The majority of the refraction seismic data show mantle phases with offsets up to 70 km. The arrivals of seismic phases were picked and used to generate a 2-D P-wave velocity model. The results show a crust-mantle boundary in the central basin at ~12 km depth below sea surface. The P-wave velocities in the crust reach 6.6 km/s at the base. The uppermost mantle shows velocities 〉7.8 km/s. The crust-mantle boundary becomes shallower from ~18 km to ~12 km depth within 30 km from Corsica towards the basin centre. The velocity model does not reveal an axial valley as expected for oceanic spreading. Further, it is difficult to interpret the seismic data whether the continental lithosphere was thinned until the mantle was exposed to the seafloor. However, an extremely thinned continental crust indicates a long lasting rifting process that possibly did not initiate oceanic spreading before the opening of the Ligurian Basin stopped. The distribution of earthquakes and their fault plane solutions, projected along our seismic velocity model, is in-line with the counter-clockwise opening of the Ligurian Basin.

Description: Volcanic eruptionsand earthquakes in the Christiana-Santorini-Kolumbo rift have repeatedly triggered devastating tsunamis including the 1600 BC Late Bronze Age eruption of Santorini, the 1650 eruption of Kolumbo and the 1956 Amorgos earthquake. The Late Bronze Age eruptiontsunami affected large areas of the eastern Mediterranean and contributed to the demise of the Minoan culture on Crete, while the effects of the 1650 Kolumbo and the 1956 Amorgos tsunamis were limited to the islands around the Christiana-Santorini-Kolumborift. Although intensively studied in recent decades, the potential tsunami source parameters of these events remain poorly constrained. The THESEUS project aims to parameterize various potential source parameters associated with these tsunami events using marine high-resolution reflection seismics. For this purpose, we conducted high-resolution 2D and 3D reflection seismic surveys as well as ocean-bottom seismometer refraction seismic experiments covering the Christiana-Santorini-Kolumbo rift during expedition POS538 onboard RV Poseidon in October 2019. Here, we present the first results of the ongoing analysis of our P-Cable 3D seismic dataset, which covers most of the Kolumbo volcanic edifice and a prominent fault zone to the north. In addition, we present 2D seismic profiles covering the Santorini Caldera and pyroclastic flow deposits associated with the Late Bronze Age eruption

Description: On 1 April 2014, the Mw 8.1 Iquique earthquake broke the plate-boundary along the North Chilean margin in the region between 19.5°S and 21°S. During this event, seismic rupture concentrated under the marine forearc with an updip limit at a plate-boundary depth of 17 km under the middle continental slope. In late 2016, wide-aperture seismic reflection and refraction data were acquired aboard the R/V Marcus G. Langsethoffshore Northern Chile as part of the “Pisagua/Iquique Crustal Tomography to Understand the Region of the Earthquake Source” (PICTURES) project. Utilizing multiple suppression techniques and ray-based tomographic inversion, we have achieved enhanced pre-stack depth migrated images to a depth of 40 km. Seismic lines MC23 and MC25, located in the southern part of the 2014 rupture area, display a pronounced plate boundary reflection that can be tracked to a depth of ~16 km. In contrast, on line MC04, located north of the 2014 rupture area, a plate boundary reflection is clearly visible to ~40 km depth. We consider that changes in fluid pressure cause the observed spatial variations in the downdip extent of the reflective plate boundary and thus may exert an influence on seismic rupture. However, the processes that control the spatial variations in fluid pressure over short distances remain enigmatic. Temperature controlled dehydration processes within the shallow subduction zone are expected to change only gradually along the margin and may therefore not explain short wavelength changes in the downdip extent of high reflectivity between line MC04 in the north and the other lines farther south. We notice, however, that the vertical displacement induced by bending related normal faults in the oceanic plate is significantly smaller along line MC04 compared to lines MC23 and MC25. This may lead to a delayed vertical flow of pore-fluids from the oceanic basement towards the plate boundary along line MC04. In contrast to lines MC23 and MC25, where fluids are expelled from the oceanic basement at relatively shallow depth along the plate boundary (i.e. under the outermost wedge), they are subducted to greater depths at the location of line MC04.

Description: The Danube deep-sea fan complex in the north-western Black Sea, with its ancient channel-levee systems, hosts multiple bottom-simulating reflections (BSRs) that have been observedin high-resolution reflection seismic data. The multiple BSRs indicate the presence of gas hydrates and free gas. To image the distribution of free gas and gas hydrates on the western flank of the S2 canyon, simultaneously, ocean bottom seismometer (OBS) data and 2-D high-resolution multichannel reflection seismic (HRMRS) data were acquired during the R/V Maria S. Merian (MSM-34) expedition. Along two parallel HRMRS-OBS profiles we recorded the wave field for a wide range of incidence angles. The velocity-structure models for both, P-and S-wave traveltimes, cover a depth down to 1.2 km, providing seismic velocity information below the BSR. For identification of the P-wave phases from OBS to OBS, we aligned the OBS data at zero offset to the 2-D HRMS data at each OBS location. The P-wave velocities show a gradual increase with depth from 1510 m/s directly beneath the seafloor up to 1900 m/s at 1.2 km depth. As the S-waves travel at slower speed than P-waves, S-waves reflection could be traced only in a smallsource-receiver offset with a maximum of ~0.9 km. We assume the reflection horizon to be the point of P-to-S conversion. Seismic S-wave velocities increase from 140 m/s beneath the seafloor up to 860 m/s at 1.2 km depth. These observations allow the determination of the P-to-S-ratio that decreases from 10.6 beneath the seafloor down to 2.2 at 1.2 km depth. The seismic velocities and P-to-S-ratio exclude the presence of gas hydrates above the BSR, but endorse the accumulation of a low concentration of free gas below. The distribution of the gas is predominately controlled by lithology.

Description: Bottom contact trawling from commercial fishing activity can have profound impacts on the sea floor, as trawling gear can both resuspend the surface sediments and shift sediment to the sides of the gear, forming furrows and mounds. This disturbance can thus have profound impacts on the benthic biogeochemistry, as these surface sediments generally contain the most labile organic matter, and the porewaters can be elevated in dissolved redox-sensitive metals (Fe and Mn). Disturbance can thus mix these Fe- and Mn- rich porewaters with oxygenated bottom waters, which can reoxidize and form particles, potentially making their distribution more heterogeneous and acting as a substrate for sorption processes. As these particulate iron oxy(hydr)oxides and manganese oxides can be reduced by the sulfide produced by microbial sulfate reduction, the distribution of these phases has profound implications for the habitability of surface sediments by modifying sulfide concentrations and related toxicity for higher life. Here, we report on a research endeavor in Fehmarn Belt, an extensively fished region in the Southern Baltic Sea, Germany. Inside of this area, we collected sediment cores from a variety of sites ranging from undisturbed (due to a nearby shipwreck and boulders) to heavily trawled. From these cores we analyzed a suite of porewater parameters (including: dissolved sulfide, Fe, Mn, SO4, nutrients, and 13C-DIC), solid phase parameters (including: Hg, TIC, CNS, reactive Fe, and reactive Mn), as well as rates of sulfate reduction (SRR). Due to the addition of an ultra-short baseline acoustic positioning system (USBL) on our multicorer (MUC), we are able to relate these parameters not just to coarse estimates of areal trawling density, but also obtain a fine (about 1 m) estimate of the MUC location in relation to specific trawl marks. Thus, we are well equipped to broaden our understanding of the impact of bottom contact trawling on benthic biogeochemical element cycling.

Description: 31.08.-05.09.2021

Description: The vast majority of active volcanism that is located at plate boundaries can be easily explained by plate tectonic processes. Intraplate volcanism, which incorporates some of the smallest and largest volcanic events on Earth, cannot be successfully explained by a single process or model. The most volumetrically significant intraplate volcanic events are associated with the arrival of the head of a thermo-chemical anomaly rising from the deep mantle and impacting the base of the lithosphere. This event generates massive and short-lived magmatic activity over a wide area (up to 2000 km across), forming a large igneous province. A long-lived hotspot track can form over the mantle plume tail and is best illustrated by the formation of age progressive volcanic chains, such as the famous Hawaiian-Emperor chain. Millions of smaller solitary volcanic edifices, non-age progressive volcanic chains and provinces, on the other hand, have other potential mechanisms of origin. Potential models comprise decompression melting due to lithospheric extension, destabilization of fusible lithologies in the lithospheric mantle, small scale sub-lithospheric convection, or lithospheric delamination.

Description: TRANSFORMERS ; Emden, Deutschland (11.01.2021) – Emden, Deutschland (14.02.2021)