Sector collapse kinematics and tsunami implications - SEKT, Cruise No. M154/1, April 3 - April 25, 2019, Mindelo (Cape Verde) - Point-á-Pitre (Guadeloupe)

Summary Deep-seated collapses of volcanic islands have generated the largest volume mass flows worldwide. These mass flows might trigger mega-tsunamis. The way in which these collapse events are emplaced is poorly understood, even though this emplacement process determines the scale of associated tsunamis. Key questions such as whether they are emplaced in single or multiple events, how they may incorporate seafloor sediment to increase their volume, and how they are related to volcanic eruption cycles and migration of volcanic centers, remain to be answered. This project forms a part of the comprehensive study of large volcanic island landslide deposits and is directly linked to IODP drilling campaign in the Lesser Antilles (IODP Leg 340). Unfortunately, Leg 340 only recovered material from a single site within the volcanic landslide deposits off Montserrat, and even at this site, recovery was not continuous. This single IODP site is insufficient to document lateral variation in landslide character, which is critical for understanding how it was emplaced. The main scientific goals of this project are to determine where the landslides are sourced from; to understand how these landslides are emplaced; and to understand the relationship between landslides, eruption cycles and initiation of new volcanic centres. Combining 3D seismology (Leg 1) and MeBo cores (Leg 2) provides a unique dataset of the internal structure, composition and source of material throughout a volcanic island landslide. The results will significantly contribute to understanding the emplacement of volcanic island landslides and they will allow us to assess the associated tsunami risk

Multiscale characterisation of chimneys/pipes: Fluid escape structures within sedimentary basins

Evaluation of seismic reflection data has identified the presence of fluid escape structures cross-cutting overburden stratigraphy within sedimentary basins globally. Seismically-imaged chimneys/pipes are considered to be possible pathways for fluid flow, which may hydraulically connect deeper strata to the seabed. The properties of fluid migration pathways through the overburden must be constrained to enable secure, long-term subsurface carbon dioxide (CO2) storage. We have investigated a site of natural active fluid escape in the North Sea, the Scanner pockmark complex, to determine the physical characteristics of focused fluid conduits, and how they control fluid flow. Here we show that a multi-scale, multi-disciplinary experimental approach is required for complete characterisation of fluid escape structures. Geophysical techniques are necessary to resolve fracture geometry and subsurface structure (e.g., multi-frequency seismics) and physical parameters of sediments (e.g., controlled source electromagnetics) across a wide range of length scales (m to km). At smaller (mm to cm) scales, sediment cores were sampled directly and their physical and chemical properties assessed using laboratory-based methods. Numerical modelling approaches bridge the resolution gap, though their validity is dependent on calibration and constraint from field and laboratory experimental data. Further, time-lapse seismic and acoustic methods capable of resolving temporal changes are key for determining fluid flux. Future optimisation of experiment resource use may be facilitated by the installation of permanent seabed infrastructure, and replacement of manual data processing with automated workflows. This study can be used to inform measurement, monitoring and verification workflows that will assist policymaking, regulation, and best practice for CO2 subsurface storage operations

Towards improved monitoring of offshore carbon storage: A real-world field experiment detecting a controlled sub-seafloor CO2 release

Carbon capture and storage (CCS) is a key technology to reduce carbon dioxide (CO2) emissions from industrial processes in a feasible, substantial, and timely manner. For geological CO2 storage to be safe, reliable, and accepted by society, robust strategies for CO2 leakage detection, quantification and management are crucial. The STEMM-CCS (Strategies for Environmental Monitoring of Marine Carbon Capture and Storage) project aimed to provide techniques and understanding to enable and inform cost-effective monitoring of CCS sites in the marine environment. A controlled CO2 release experiment was carried out in the central North Sea, designed to mimic an unintended emission of CO2 from a subsurface CO2 storage site to the seafloor. A total of 675 kg of CO2 were released into the shallow sediments (∼3 m below seafloor), at flow rates between 6 and 143 kg/d. A combination of novel techniques, adapted versions of existing techniques, and well-proven standard techniques were used to detect, characterise and quantify gaseous and dissolved CO2 in the sediments and the overlying seawater. This paper provides an overview of this ambitious field experiment. We describe the preparatory work prior to the release experiment, the experimental layout and procedures, the methods tested, and summarise the main results and the lessons learnt

Rolled-Up Vertical Microcavities Studied by Evanescent Wave Coupling and Photoluminescence Spectroscopy

Vertically rolled-up microcavities are fabricated using differentially strained nanomembranes by employing rate and temperature gradients during electron beam evaporation of SiO2. The geometry of the rolled-up tubes is defined by a photo-lithographically patterned polymer sacrificial layer beneath the SiO2 layers that is dissolved to start the rolling. Rolled-up tubes support resonances formed by constructive interference of light propagating along the circumference. Optical studies are performed in the visible spectral range using a micro-photoluminescence (µPL) setup to excite and detect optical modes. Record high quality factors (Q factors) of 5400 for rolled-up resonators probed in PL-emission mode are found and their limits are theoretically investigated. Axial modes can also be supported when an increased winding number in the center is realized by appropriate pattern designs. In addition, higher order radial modes can be confined when atomic layer deposition (ALD) coatings are applied. Both types of modes are identified using polarization and spatially resolved µPL maps. Evanescent-wave coupling by tapered fibers and tubes on substrates is the second method used to study light confinement and to demonstrate frequency filtering in ALD coated rolled-up microcavities. Scans are performed by monitoring light from a tunable laser in the range of 1520-1570 nm after transmission through the tapered fiber. Dips in the spectrum are found and attributed to fundamental and axial resonant modes. Moreover, by coupling two tapered fibers to a lifted rolled-up microcavity, a four-port add-drop filter is demonstrated as a future component for vertical resonant light transfer in on-chip optical networks. Simulations show that the subwavelength tube wall thickness limits the Q factor at infrared wavelengths and ALD coatings are necessary to enhance the light confinement. After coating, two linear polarization states are found in experiment and fundamental and axial modes can be selectively excited by coupling the fiber to different positions along the tube axis. Spatially and polarization resolved transmission maps reveal a polarization dependent axial mode distribution which is verified theoretically. The results of this thesis are important for lab-on-chip applications where rolled-up microcavities are employed as high resolution optofluidic sensors as well as for future uses as waveguide coupled components in three-dimensional multi-level optical data processing units to provide resonant interlayer signal transfer

Functional relevance of the protein-protein interaction between the tobacco ankyrin-repeat protein ANK1 and the bZIP transcription factor BZI-1 within herbal auxin and pathogen response

Für den Tabak (Nicotiana tabacum) bZIP-Transkriptionsfaktor BZI-1 konnte eine Beteiligung an der Auxinantwort und am Tabak Mosaik Virus (TMV) induzierten hypersensitiven Zelltod gezeigt werden (Kuhlmann et al., 2003; Heinekamp et al., 2004). Eine Heterodimerisierung mit dem bZIP-Transkriptionsfaktor BZI-2 konnte mit Hilfe des Hefe Two-Hybrid nachgewiesen werden (Strathmann et al., 2001). Mittels Protoplasten Two-Hybrid und Bimolecular Fluorescence Complementation Analysen ließ sich eine spezifische in planta Interaktion zwischen BZI-1 und dem Ankyrin-Repeat Protein ANK1 nachweisen. Diese Interaktion wird auf der Seite von BZI-1 durch die a-helikale Domäne DI und auf der Seite von ANK1 durch die Ankyrin-Repeats vermittelt. Ziel der Arbeit war die funktionellen Charakterisierung des Transkriptionsfaktors BZI-1 und des Ankyrin-Repeat Proteins ANK1.Mit Hilfe der Expression von YFP-Fusionsproteinen konnte ANK1 im Cytosol und BZI-1 im Zellkern lokalisiert werden. Die Inhibierung des Kernexportes und Auxingabe führen zur Akkumulation von ANK1 im Zellkern von Tabak Mesophyllprotoplasten. Durch Co-Expression von ANK1 zusätzlich zu BZI-1 und BZI-2, wird die BZI-1/BZI-2 vermittelte Auxin abhängige Transkription verstärkt. Damit fungiert ANK1 möglicherweise als ein Co-Aktivator von BZI-1. Transgene Pflanzen in denen die Expression von ANK1, BZI-1 oder BZI-2 mittels eines RNA-Interferenz Ansatzes (RNAi) reduziert ist, zeigen eine deutlich abgeschwächte Auxinantwort. Nach der Infektion mit dem Tabak Mosaik Virus ist der hypersensitive Zelltod in den ANK1- und BZI-1-RNAi Pflanzen verstärkt. Da die ANK1- und BZI-1-RNAi Pflanzen vergleichbare Phänotypen zeigen, wird eine biologische Bedeutung der ANK1/BZI-1 Interaktion in der Regulation der pflanzlichen Auxinantwort und des TMV-induzierten hypersensitiven Zelltods postuliert.The tobacco (Nicotiana tabacum) bZIP transcription factor BZI-1 participates in auxin response and the tobacco mosaic virus (TMV) induced hypersensitive response (Kuhlmann et al., 2003; Heinekamp et al., 2004). Strathmann et al. (2001) could show a heterodimerisation of BZI-1 with the bZIP transcription factor BZI-2. Using protoplast Two-Hybrid and Bimolecular Fluorescence Complementation approaches a specific in planta interaction between BZI-1 and the ankyrin-repeat protein ANK1 could be detected. This interaction is mediated by the a-helical domain DI of BZI-1 and the ankyrin-repeats of ANK1. Aim of this study was the functional characterisation of the transcription factor BZI-1 and the ankyrin-repeat protein ANK1.After expression of YFP fusion proteins, ANK1 was found to be localized in the cytosol and BZI-1 in the nucleus. Inhibition of the nuclear export and the induction with auxin both induce accumulation of ANK1 in the nucleus of tobacco mesophyll protoplasts. Co-expression of ANK1 additionally to BZI-1 and BZI-2 leads to an increase of the BZI-1/BZI-2 mediated auxin dependant transcription. Hence, it is assumed that ANK1 acts as a co-activator of BZI-1. In transgenic RNA-interference plants with reduced ANK1, BZI-1 or BZI-2 expression auxin responses are strongly reduced. After infection with the tobacco mosaic virus, the hypersensitive cell death is increased in ANK1- and BZI-1-RNAi plants. Because of the comparable phenotypes of the ANK1- and BZI-1-RNAi plants a biological relevance of the ANK1/BZI-1 interaction in regulation of auxin responses and TMV induced hypersensitive cell death is postulated

Dynamics and variability of POC burial in depocenters of the North Sea (Skagerrak), Cruise No. AL561, 2.08.2021 – 13.08.2021, Kiel – Kiel, APOC

The AL561 cruise was conducted in the framework of the project APOC (“Anthropogenic impacts on Particulate Organic Carbon cycling in the North Sea”). This collaborative project between GEOMAR, AWI, HEREON, UHH, and BUND is to understand how particulate organic carbon (POC) cycling contributes to carbon sequestration in the North Sea and how this ecosystem service is compromised and interlinked with global change and a range of human pressures include fisheries (pelagic fisheries, bottom trawling), resource extraction (sand mining), sediment management (dredging and disposal of dredged sediments) and eutrophication. The main aim of the sampling activity during AL561 cruise was to recover undisturbed sediment from high accumulation sites in the Skagerrak/Kattegat and to subsample sediment/porewater at high resolution in order to investigate sedimentation transport processes, origin of sediment/POC and mineralization processes over the last 100- 200 years. Moreover, the actual processes of sedimentation and POC degradation in the water column and benthic layer will be addressed by sampling with CTD and Lander devices. In total 9 hydroacoustic surveys (59 profiles), 4 Gravity Corer, 7 Multicorer, 3 Lander and 4 CTD stations were successfully conducted during the AL561 cruise

Modelling mass accumulation rates and 210Pb rain rates in the Skagerrak: lateral sediment transport dominates the sediment input

Sediment fluxes to the seafloor govern the fate of elements and compounds in the ocean and serve as a prerequisite for research on elemental cycling, benthic processes and sediment management strategies. To quantify these fluxes over seafloor areas, it is necessary to scale up sediment mass accumulation rates (MAR) obtained from multiple sample stations. Conventional methods for spatial upscaling involve averaging of data or spatial interpolation. However, these approaches may not be sufficiently precise to account for spatial variations of MAR, leading to poorly constrained regional sediment budgets. Here, we utilize a machine learning approach to scale up porosity and 210 Pb data from 145 and 65 stations, respectively, in the Skagerrak. The models predict the spatial distributions by considering several predictor variables that are assumed to control porosity and 210 Pb rain rates. The spatial distribution of MAR is based on the predicted porosity and existing sedimentation rate data. Our findings reveal highest MAR and 210 Pb rain rates to occur in two parallel belt structures that align with the general circulation pattern in the Skagerrak. While high 210 Pb rain rates occur in intermediate water depths, the belt of high MAR is situated closer to the coastlines due to lower porosities at shallow water depths. Based on the spatial distributions, we calculate a total MAR of 34.7 Mt yr -1 and a 210 Pb rain rate of 4.7 · 10 14 dpm yr -1 . By comparing atmospheric to total 210 Pb rain rates, we further estimate that 24% of the 210 Pb originates from the local atmospheric input, with the remaining 76% being transported laterally into the Skagerrak. The updated MAR in the Skagerrak is combined with literature data on other major sediment sources and sinks to present a tentative sediment budget for the North Sea, which reveals an imbalance with sediment outputs exceeding the inputs. Substantial uncertainties in the revised Skagerrak MAR and the literature data might close this imbalance. However, we further hypothesize that previous estimates of suspended sediment inputs into the North Sea might have been underestimated, considering recently revised and elevated estimates on coastal erosion rates in the surrounding region of the North Sea