ALBERT

Description: The Black Sea has undergone several limnic and marine stages due to fluctuations in the global sea level. The exchange of saline water from the Mediterranean Sea to the Black Sea through the Bosporus Strait was interrupted when the sea level dropped below the Bosporus sill. This induced limnic conditions, while marine conditions were established after the reconnection to saline Mediterranean seawater. Extended river fan systems developed during sea level low-stands, providing large amounts of organic material being buried by rapid sedimentation on the slopes of the Black Sea margins. The biogenic degradation of this material produces most of the methane gas expelled into the anoxic water column today. This largely happens by ubiquitous cold vents at ~700 m water depth (i.e. at the stability boundary of methane hydrates) and by mud volcanoes in ~2000 m water depth. A significant amount of gas is expected to accumulate in the sediment within the methane hydrate stability zone. However, bottom-simulating reflectors, the seismic indicator for gas hydrates, are not found everywhere along the margin. Recent analyses of the Danube and Dniepr fans have revealed a discontinuous gas hydrate formation in an area with no active seeps, while areas of active seepage located in the vicinity of BSR reflections held no gas hydrates. In addition, the ongoing diffusion of salt into the uppermost Black Sea sediment pore space since the last glacial maximum further reduces the volume of the gas hydrate stability zone. Estimates of the total amount of gas stored in gas hydrates therefore require a detailed structural analysis prior to regional- or basin-scale modelling attempts.

Description: Marine electromagnetic methods provide useful and independent measures for the identification and quantification of submarine gas hydrates. The resistivity of seafloor sediments, drawn from area-wide electromagnetic data, mainly depends on the sediment porosity and the nature of the pore fluid. Gas hydrates and free gas are both electrically resistive. The replacement of saline water, thus conductive pore water with resistive gas hydrate or free gas, increases the sediment resistivity and can be used to provide accurate saturation estimates if the background lithology is known. While seismic methods are predominantly used to study the distribution of submarine gas hydrates, a growing number of global field studies have demonstrated that the joint interpretation of marine seismic and electromagnetic methods improves the evaluation of submarine gas hydrate targets. This article discusses the relationship between resistivity and free gas/gas hydrate saturation levels, how the resistivity of the sediment may be measured and summarizes the status and results of current and past field studies.

Description: Every year, vast quantities of plastic debris arrive at the ocean surface. Nevertheless, our understanding of plastic movements is largely incomplete and many of the processes involved with the horizontal and vertical displacement of plastics in the ocean are still basically unknown. In this chapter we review the dynamics associated with the transport of plastics and other pollutants at oceanic fronts. Fronts had been historically defined as simple barriers to exchange, but here we show that the role of these structures in influencing the transport of plastics is more complex. The tools used to investigate the occurrence of frontal structures at various spatial scales are reviewed in detail, with a particular focus on their potential applications to the study of plastic pollution. Three selected case studies are presented to better describe the role of fronts in favoring or preventing plastic exchanges: the large-scale Antarctic Circumpolar Current, a Mediterranean mesoscale front, and the submesoscale fronts in the Gulf of Mexico. Lastly, some aspects related to the vertical subduction of plastic particles at oceanic fronts are discussed as one of the most promising frontiers for future research. The accumulation of floating debris at the sea surface is mainly affected by the horizontal components of frontal dynamics. At the same time, vertical components can be relevant for the export of neutrally buoyant particles from the surface into the deep sea. Based on these evidences, we propose that submesoscale processes can provide a fast and efficient route of plastic transport within the mixed layer, while mesoscale instabilities and associated vertical velocities might be the dominant mechanism to penetrate the deeper ocean on slower but broader scales. We conclude that given the ubiquitous presence of fronts in the world’s ocean, their contribution to the global plastic cycle is probably not negligible and the role of these processes in vertically displacing neutrally buoyant microplastics should be investigated in more detail.

Description: The Barents Sea, located close to the Arctic Ocean, is a petroleum province featuring an extensive occurrence of gas hydrates and shallow gas in compacted sediments. Glacial erosion and uplift have contributed to the migration of gas originating from deeper rocks to the shallow sediments of this region, resulting in hydrates with higher-order hydrocarbons in addition to methane. This article documents reported gas hydrate indications and major controls on hydrate stability in the Barents Sea.

Description: Since global navigation satellite systems (GNSS) for determining the absolute geolocation do not reach into the ocean, underwater robots typically obtain a GNSS position at the water surface and then use a combination of different sensors for estimating their pose while diving, including inertial navigation, acoustic doppler velocity logs, ultra short baseline localization systems and pressure sensors. When re-navigating to the same seafloor location after several days, months or years, e.g. for coastal monitoring, the absolute uncertainty of such systems can be in the range of meters for shallow water, and tens of meters for deeper waters in practice. To enable absolute relocalization in marine data science applications that require absolute seafloor positions in the range of centimeter precision, in this contribution we suggest to equip the monitoring area with visual markers that can be detected reliably even in case they are partially overgrown or partially buried by sediment, which can happen quickly in coastal waters. Inspired by patterns successful in camera calibration, we create robust markers that exhibit features at different scales, in order to allow detection, identification and pose estimation from different cameras and various altitudes as visibility (and therefore the maximum possible survey altitude) in coastal waters can vary significantly across seasons, tides and weather. The low frequency content of the marker resembles a human-readable digit, in order to allow easy identification by scientists. We present early results including promising initial tests in coastal waters.

Description: While offshore groundwater has been utilized by coastal communities as far back as 1000 BC, only in the past 10 years has the global volume of fresh-to-brackish water hosted in offshore aquifers been truly appreciated. There are vast quantities (~300–500 × 103 km3) of offshore freshened groundwater sequestered in continental shelf sediments under water depths of less than 60 m within 110 km of the coastline. New marine geophysical methods now make it possible to map and quantify low salinity offshore groundwater bodies. To date, these offshore resources have not been developed. Offshore freshened groundwater could be produced if wells are located close to the shoreline and coastal desalination plants.

Description: Underwater images are challenging for correspondence search algorithms, which are traditionally designed based on images captured in air and under uniform illumination. In water however, medium interactions have a much higher impact on the light propagation. Absorption and scattering cause wavelength- and distance-dependent color distortion, blurring and contrast reductions. For deeper or turbid waters, artificial illumination is required that usually moves rigidly with the camera and thus increases the appearance differences of the same seafloor spot in different images. Correspondence search, e.g. using image features, is however a core task in underwater visual navigation employed in seafloor surveys and is also required for 3D reconstruction, image retrieval and object detection. For underwater images, it has to be robust against the challenging imaging conditions to avoid decreased accuracy or even failure of computer vision algorithms. However, explicitly taking underwater nuisances into account during the feature extraction and matching process is challenging. On the other hand, learned feature extraction models achieved high performance in many in-air problems in recent years. Hence we investigate, how such a learned robust feature model, D2Net, can be applied to the underwater environment and particularly look into the issue of cross domain transfer learning as a strategy to deal with the lack of annotated underwater training data.

Description: Fish food is an inevitable item in human consumption with healthy sourceof good quality proteins and fat. Aqua industry can help to improve food security,livelihoods for the poorest and to meet the world’s food demands. But producingmore seafood that is at affordable cost with rich nutrition is challenging for aquaindustry. Many factors affect the productivity of aqua industry; one such an impor-tant constraint is bacterial diseases. Hence, Aqua industry, a booming businesssector, immensely requires continued research with scientific and technical devel-opments, and innovations. Study of bacterialfish disease is one such thrust areawhich requires intense research to understand the causes and control bacterialdiseases infish. The appearance and development of afish disease is the result ofthe interaction among pathogen, host and environment. An insight into bacterialfishdiseases, clinical symptoms and treatment may help to manage the bacterial diseasesand so can make aqua industry a more profitablefield. This chapter deals withdifferent aspects of the most threatening bacterial diseases, occurring in farmedfishes and also in wildfishes, which are results infish loss and economic lossworldwide. A wide range of gram positive and gram-negative bacteria causingbacterial diseases, clinical symptoms, diagnosis, treatment, vaccines and the natureof water habitat are also discussed in this chapter.

Description: The Digital Earth project aimed for the integration of data science and Earth science. Here, we reflect on the main lessons learned that include the need for interdisciplinary collaboration, thinking out of the box, the concept of ‘thinking in workflows’ and models for the sustainable implementation of scientific software, data infrastructure and policies.

Description: Digital Earth is a project funded by the German Helmholtz Association with all centers of the research field Earth and Environment involved. The main goal of the Digital Earth project is to develop and bundle data science methods in extendable and maintainable scientific workflows that enable natural scientists in collaboration with data scientists to achieve a deeper understanding of the Earth system. This has been achieved by developing solutions for data analysis and exploration with visual and computational approaches with data obtained in a SMART monitoring approach and modeling studies, accompanied by a continuous evaluation of the collaboration processes. In this chapter, the history, setup, and focus of the Digital Earth project are described.

Description: The Digital Earth project aims at a strong interrelation between Data and Earth Science and a step-change in implementing data science methods within Earth science research. During the project, the progress of interdisciplinary collaboration and adoption of data science methods has been measured and assessed with the goal to trace the success of the project. This chapter provides the set-up of this evaluation and the results from two online questionnaires that were held after the start and before the end of the project.

Description: Diversity within marine microbiomes spans the three domains of life: microbial eukaryotes (i.e., protists), bacteria, and archaea. Although protists were the first microbes observed by microscopy, it took the advent of molecular techniques to begin to resolve their complex and reticulate evolutionary history. Symbioses between microbial entities have been key in this journey, and such interactions continue to shape the ecology of marine microbiomes. Nowadays, photosynthetic marine protists are appreciated for their activities as primary producers, rivalling land plant contributions in the global carbon cycle. Predatory protists are known for consuming prokaryotes and other protists, with some combining metabolisms into a mixotrophic lifestyle. Still, much must be learned about specific interactions and lifestyles, especially for uncultured groups recognized just by environmental sequences. With respect to the fate of protists in food webs, there are many paths to consider. Despite being in early stages of identifying interactions, whether mutualistic or death-inducing infections by parasites and viruses, knowledge is advancing rapidly via methods for interrogation in nature without culturing. Here, we review marine protists, their evolutionary histories, diversity, ecological roles, and lifestyles in all layers of the ocean, with reference to how views have shifted over time through extensive investigation.

Description: This dataset contains PISM simulation results of the Antarctic Ice Sheet based on code release v1.0-paleo-ensemble (https://doi.org/10.5281/zenodo.3574033). PISM is the open-source Parallel Ice Sheet Model developed mainly at UAF, USA and PIK, Germany. See documentation in https://www.pism.io. These are additional netCDF data from the same ensemble simulations already stored in doi:10.1594/PANGAEA.909728. 1) 1000-year snapshots since 125000 years before present, of ice thickness, bed topography, change in bed topography, floating/grounded mask, surface elevation, basal melt rate and vertically averaged velocity magnitude (SIA+SSA) (16GB) 2) 5000-year snapshots since 125000 years before present, SSA velocity components in x and y direction (8GB)

Description: Data-driven science has turned into a fourth fundamental paradigm of performing research. Earth System Science, following a holistic approach in unraveling the complex network of processes and interactions shaping system Earth, particularly profits from embracing data-driven approaches next to observation and modeling. At the end, increasing digitalization of Earth sciences will lead to cultural transformation towards a Digital Earth Culture.

Description: A comprehensive study of the Earth system and its related processes requires a holistic examination and understanding of multidimensional data acquired with a large number of different sensors or produced by various models. To this end, the Digital Earth project developed a set of software solutions to study environmental data sets using visual approaches. In the following chapter, we present three data visualization products developed to deal with the challenges of the analysis and exploration of environmental data.

Description: Reliable data are the base of all scientific analyses, interpretations and conclusions. Evaluating data in a smart way speeds up the process of interpretation and conclusion and highlights where, when and how additionally acquired data in the field will support knowledge gain. An extended SMART monitoring concept is introduced which includes SMART sensors, DataFlows, MetaData and Sampling approaches and tools. In the course of the Digital Earth project, the meaning of SMART monitoring has significantly evolved. It stands for a combination of hard- and software tools enhancing the traditional monitoring approach where a SMART monitoring DataFlow is processed and analyzed sequentially on the way from the sensor to a repository into an integrated analysis approach. The measured values itself, its metadata, and the status of the sensor, and additional auxiliary data can be made available in real time and analyzed to enhance the sensor output concerning accuracy and precision. Although several parts of the four tools are known, technically feasible and sometimes applied in Earth science studies, there is a large discrepancy between knowledge and our derived ambitions and what is feasible and commonly done in the reality and in the field.

Description: Global population projections foresee the biggest increase to occur in Africa with most of the available uncultivated land to ensure food security remaining on the continent. Simultaneously, greenhouse gas emissions are expected to rise due to ongoing land use change, industrialisation, and transport amongst other reasons with Africa becoming a major emitter of greenhouse gases globally. However, distinct knowledge on greenhouse gas emissions sources and sinks as well as their variability remains largely unknown caused by its vast size and diversity and an according lack of observations across the continent. Thus, an environmental research infrastructure—as being setup in other regions—is more needed than ever. Here, we present the results of a design study that developed a blueprint for establishing such an environmental research infrastructure in Africa. The blueprint comprises an inventory of already existing observations, the spatial disaggregation of locations that will enable to reduce the uncertainty in climate forcing’s in Africa and globally as well as an overall estimated cost for such an endeavour of about 550 M€ over the next 30 years. We further highlight the importance of the development of an e-infrastructure, the necessity for capacity development and the inclusion of all stakeholders to ensure African ownership.

Description: It is a good method to utilize the grain size distribution curves and cumulative frequency curves of marine or river sediments to estimate the hydrodynamic conditions, transportation processes and sedimentary environment. However, researchers can only rely on Excel or Grapher to plot the curves one by one at the present day. The manual plotting procedures are complicated, and calculating the truncation points is time-consuming. To solve the aforementioned problems, we have developed a software tool to plot cumulative frequency curves and calculate the values of truncation points automatically. The software has the ability to plot curves of hundreds of samples accurately and rapidly, promoting researchers to analyze transport mechanisms and hydrodynamic environments. And it is convenient to apply the software to compare the processes of transportation and deposition between different samples.

Description: In times of accelerating climate change, species are challenged to respond to rapidly shifting environmental settings. Yet, faunal distribution and composition are still scarcely known for remote and little explored seas, where observations are limited in number and mostly refer to local scales. Here, we present the first comprehensive study on Eurasian-Arctic macrobenthos that aims to unravel the relative influence of distinct spatial scales and environmental factors in determining their large-scale distribution and composition patterns. To consider the spatial structure of benthic distribution patterns in response to environmental forcing, we applied Moran’s eigenvector mapping (MEM) on a large dataset of 341 samples from the Barents, Kara and Laptev Seas taken between 1991 and 2014, with a total of 403 macrobenthic taxa (species or genera) that were present in ≥ 10 samples. MEM analysis revealed three spatial scales describing patterns within or beyond single seas (broad: ≥ 400 km, meso: 100–400 km, and small: ≤ 100 km). Each scale is associated with a characteristic benthic fauna and environmental drivers (broad: apparent oxygen utilization and phosphate, meso: distance-to-shoreline and temperature, small: organic carbon flux and distance-to-shoreline). Our results suggest that different environmental factors determine the variation of Eurasian-Arctic benthic community composition within the spatial scales considered and highlight the importance of considering the diverse spatial structure of species communities in marine ecosystems. This multiple-scale approach facilitates an enhanced understanding of the impact of climate-driven environmental changes that is necessary for developing appropriate management strategies for the conservation and sustainable utilization of Arctic marine systems.

Description: Cold-water coral (CWC) reefs constitute one of the most complex deep-sea habitats harboring a vast diversity of associated species. Like other tropical or temperate framework builders, these systems are facing an uncertain future due to several threats, such as global warming and ocean acidification. In the case of Mediterranean CWC communities, the effect may be exacerbated due to the greater capacity of these waters to absorb atmospheric CO2 compared to the global ocean. Calcification in these organisms is an energy-demanding process, and it is expected that energy requirements will be greater as seawater pH and the availability of carbonate ions decrease. Therefore, studies assessing the effect of a pH decrease in skeletal growth, and metabolic balance are critical to fully understand the potential responses of these organisms under a changing scenario. In this context, the present work aims to investigate the medium- to long-term effect of a low pH scenario on calcification and the biochemical composition of two CWCs from the Mediterranean, Dendrophyllia cornigera and Desmophyllum dianthus. After 314 d of exposure to acidified conditions, a significant decrease of 70 % was observed in Desmophyllum dianthus skeletal growth rate, while Dendrophyllia cornigera showed no differences between treatments. Instead, only subtle differences between treatments were observed in the organic matter amount, lipid content, skeletal microdensity, or porosity in both species, although due to the high variability of the results, these differences were not statistically significant. Our results also confirmed a heterogeneous effect of low pH on the skeletal growth rate of the organisms depending on their initial weight, suggesting that those specimens with high calcification rates may be the most susceptible to the negative effects of acidification.

Description: Structure I methane hydrates are formed in situ from water-in-mineral oil emulsions in a high pressure rheometer cell. Viscosity is measured as hydrates form, grow, change under flow, and dissociate. Experiments are performed at varying water volume fraction in the original emulsion (0–0.40), temperature (0–6 °C), and initial pressure of methane (750–1500 psig). Hydrate slurries exhibit a sharp increase in viscosity upon hydrate formation, followed by complex behavior dictated by factors including continued hydrate formation, shear alignment, methane depletion/dissolution, aggregate formation, and capillary bridging. Hydrate slurries possess a yield stress and are shear-thinning fluids, which are described by the Cross model. Hydrate slurry viscosity and yield stress increased with increasing water volume fraction. As driving force for hydrate formation decreases (increasing temperature, decreasing pressure), hydrate slurry viscosity increases, suggesting that slower hydrate formation leads to larger and more porous aggregates. In total, addition of water to a methane saturated oil can cause more than a fifty-fold increase in viscosity if hydrates form.

Description: Marine habitats worldwide are increasingly pressurized by climate change, especially along the Antarctic Peninsula. Well-studied areas in front of rapidly retreating tidewater glaciers like Potter Cove are representative for similar coastal environments and, therefore, shed light on habitat formation and development on not only a local but also regional scale. The objective of this study was to provide insights into habitat distribution in Potter Cove, King George Island, Antarctica, and to evaluate the associated environmental processes. Furthermore, an assessment concerning the future development of the habitats is provided. To describe the seafloor habitats in Potter Cove, an acoustic seabed discrimination system (RoxAnn) was used in combination with underwater video images and sediment samples. Due to the absence of wave and current measurements in the study area, bed shear stress estimates served to delineate zones prone to sediment erosion. On the basis of the investigations, two habitat classes were identified in Potter Cove, namely soft-sediment and stone habitats that, besides influences from sediment supply and coastal morphology, are controlled by sediment erosion. A future expansion of the stone habitat is predicted if recent environmental change trends continue. Possible implications for the Potter Cove environment, and other coastal ecosystems under similar pressure, include changes in biomass and species composition.

Description: The family Rhodobacteraceae can be considered a paradigm of modern taxonomy of prokaryotes. Taking into account the number of species and genera that conforms the family, together with the knowledge about their abundance and vast global distribution, it surprises that most of them have been described relatively recent to our days. Two notable exceptions are Rhodonostoc capsulatum (Molisch, Die purpurbakterien nach neuen untersuchungen, vols i–vii. G. Fischer, Jena, pp 1–95, 1907) and Micrococcus denitrificans Beijerinck and Minkman (Zentbl Bakteriol, Parasitenkd, Infektionskr Hyg. Abt II 25:30–63, 1910), early basonyms of Rhodobacter capsulatus and Paracoccus denitrificans, respectively. The fact that so many descriptions within this family are recent means that some studies have been concomitant and pose a challenge not only for pure taxonomic studies but also for interpreting other studies in which a rapidly evolving nomenclature had to be used anyway. The metabolic and ecological diversity of the group adds further complexity. In spite of all these difficulties, the picture is far from being a chaos and it can be considered an exciting and important bacterial group to study. Rhodobacteraceae are, fundamentally, aquatic bacteria that frequently thrive in marine environments. They comprise mainly aerobic photo- and chemoheterotrophs but also purple non-sulfur bacteria which perform photosynthesis in anaerobic environments. They are deeply involved in sulfur and carbon biogeochemical cycling and symbiosis with aquatic micro- and macroorganisms. One hundred genera are currently recognized as members of the family although the Stappia group, Ahrensia, Agaricicola, and Rhodothalassium do not belong, phylogenetically, to the family. The 90 other genera are distributed in 5 phylogenetic groups (the Rhodobacter, the Paracoccus, the Rhodovulum, the Amaricoccus, and the Roseobacter clades) that might be considered a family on its own.

Description: Bacterial light production involves enzymes-luciferase, fatty acid reductase, and flavin reductase-and substrates-reduced flavin mononucleotide and long-chain fatty aldehyde-that are specific to bioluminescence in bacteria. The bacterial genes coding for these enzymes, luxA and luxB for the subunits of luciferase; luxC, luxD, and luxE for the components of the fatty acid reductase; and luxG for flavin reductase, are found as an operon in light-emitting bacteria, with the gene order, luxCDABEG. Over 30 species of marine and terrestrial bacteria, which cluster phylogenetically in Aliivibrio, Photobacterium, and Vibrio (Vibrionaceae), Shewanella (Shewanellaceae), and Photorhabdus (Enterobacteriaceae), carry lux operon genes. The luminescence operons of some of these bacteria also contain genes involved in the synthesis of riboflavin, ribEBHA, and in some species, regulatory genes luxI and luxR are associated with the lux operon. In well-studied cases, lux genes are coordinately expressed in a population density-responsive, self-inducing manner called quorum sensing. The evolutionary origins and physiological function of bioluminescence in bacteria are not well understood but are thought to relate to utilization of oxygen as a substrate in the luminescence reaction.

Description: Fertilization depends on distribution and aggregation patterns of sea urchins which influence gamete contact time and may potentially enhance their vulnerability to ocean acidification. In this study, we conducted fertilization experiments to assess the effects of selected pH scenarios on fertilization success of Strongylocentrotus droebachiensis, from Spitsbergen, Arctic. Acidification was achieved by aerating seawater with different CO2 partial pressures to represent pre-industrial and present conditions (measured ~180–425 µatm) and future acidification scenarios (~550–800, ~1,300, ~2,000 µatm). Fertilization success was defined as the proportion of successful/unsuccessful fertilizations per treatment; eggs were classified according to features of their fertilization envelope (FE), hyaline layer (HL) and achievement of cellular division. The diagnostic findings of specific pathological aberrations were described in detail. We additionally measured intracellular pH changes in unfertilized eggs exposed for 1 h to selected acidification treatments using BCECF/AM. We conclude that (a) acidified conditions increase the proportion of eggs that failed fertilization, (b) acidification may increase the risk of polyspermy due to failures in the FE formation supported by the occasional observation of multiple sperms in the perivitelline space and (c) irregular formation of the embryo may arise due to impaired formation of the HL. The decrease in fertilization success could be also related to the observed changes in intracellular pH at pCO2 ~ 1,000 μatm or higher.

Description: The 5th International Workshop on Modeling the Ocean (IWMO http://www.uib.no/en/IWMO2013/-58927/iwmo-2013-bergen-norway) was held in June 17–20, in Bergen, Norway. The historic city of Bergen is the gateway to the fjords and a center for oceanic research. The workshop was hosted by the University of Bergen and also sponsored by the Research Council of Norway. Approximately 80 researchers worldwide participated in the workshop. Professor Mellor, Princeton University, gave the keynote lecture. The 5th IWMO meeting in Bergen was the first IWMO held in Europe, followed on the footsteps of previous meetings, IWMO-2009 in Taipei, Taiwan (Oey et al. 2010a, b), IWMO-2010 in Norfolk, USA (Ezer et al. 2011), IWMO-2011 in Qingdao, China (Oey et al. 2013a), and IWMO-2012 in Yokohama, Japan (Oey et al. 2013b). The participants presented approximately 60 oral talks and 20 posters, covering a wide range of ocean modeling and data analysis topics, as described below. In the spirit of promoting young s ...

Description: The Adula Nappe in the Central Alps is a mixture of various pre-Mesozoic continental basement rocks, metabasics, ultrabasics, and Mesozoic cover rocks, which were pervasively deformed during Alpine orogeny. Metabasics, ultrabasics, and locally garnet–mica schists preserve eclogite-facies assemblages while the bulk of the nappe lacks such evidence. We provide garnet major-element data, Lu profiles, and Lu–Hf garnet geochronology from eclogites sampled along a north–south traverse. A southward increasing Alpine overprint over pre-Alpine garnets is observed throughout the nappe. Garnets in a sample from the northern Adula Nappe display a single growth cycle and yield a Variscan age of 323.8 ± 6.9 Ma. In contrast, a sample from Alpe Arami in the southernmost part contains unzoned garnets that fully equilibrated to Alpine high-pressure (HP) metamorphic conditions with temperatures exceeding 800 °C. We suggest that the respective Eocene Lu–Hf age of 34.1 ± 2.8 Ma is affected by partial re-equilibration after the Alpine pressure peak. A third sample from the central part of the nappe contains separable Alpine and Variscan garnet populations. The Alpine population yields a maximum age of 38.8 ± 4.3 Ma in line with a previously published garnet maximum age from the central nappe of 37.1 ± 0.9 Ma. The Adula Nappe represents a coherent basement unit, which preserves a continuous Alpine high-pressure metamorphic gradient. It was subducted as a whole in a single, short-lived event in the upper Eocene. Controversial HP ages and conditions in the Adula Nappe may result from partly preserved Variscan assemblages in Alpine metamorphic rocks.

Description: Ecosystems and their biodiversity have to be protected and preserved as sources of services and goods. The human population controls and modifies ecosystems to improve its health conditions and welfare. The consequences of human activities should be carefully monitored and ecosystems should be managed to protect all of the species and preserve their functioning. The development of strategies for ecosystem management benefits from the use of computational techniques to model the dynamics of species that interact with their abiotic and biotic environment. Life scientists and computer scientists need to work together to define and analyse ecosystem models. However, there is a multifaceted gap between the approaches used in life science and those used in computer science. Such gap is both cultural and technical, and results in a number of challenges. In this paper we identify these challenges and provide technical and cultural proposals for solving them.

Description: Subfossil Cladocera were sampled and examined from the surface sediments of 35 thermokarst lakes along a temperature gradient crossing the tree line in the Anabar-river basin in northwestern Yakutia, northeastern Siberia. The lakes were distributed through three environmental zones: typical tundra, southern tundra and forest tundra. All lakes were situated within the continuous permafrost zone. Our investigation showed that the cladoceran communities in the lakes of the Anabar region are diverse and abundant, as reflected by taxonomic richness, and high diversity and evenness indices (H = 1.89 ± 0.51; I = 0.8 ± 0.18). CONISS cluster analysis indicated that the cladoceran communities in the three ecological zones (typical tundra, southern tundra and forest-tundra) differed in their taxonomic composition and structure. Differences in the cladoceran assemblages were related to limnological features and geographical position, vegetation type, climate and water chemistry. The constrained redundancy analysis indicated that TJuly, water depth and both sulphate (SO4 2−) and silica (Si4+) concentrations significantly (p ≤ 0.05) explained variance in the cladoceran assemblage. TJuly featured the highest percentage (17.4 %) of explained variance in the distribution of subfossil Cladocera. One of the most significant changes in the structure of the cladoceran communities in the investigated transect was the replacement of closely related species along the latitudinal and vegetation gradient. The results demonstrate the potential for a regional cladoceran-based temperature model for the Arctic regions of Russia, and for and Yakutia in particular.

Description: A large monothalamous foraminiferan, Toxisarcon taimyr sp. nov., has been isolated from the benthic samples from the Kara Sea inner shelf near the mouth of Yenisey river estuary, at a depth of 50–100 m. In its overall morphology, the new species closely resembles T. synsuicidica, one of the two species of Toxisarcon described to date. It possesses a large irregularly shaped cell body, covered by a thin layer of a fibrous organic coating. Numerous reticulopodia typically extend from all over the cell surface; the species is very motile and rapidly changes cell shape. Long and thick reticulopodial bundles form in the direction of movement. In the phylogenetic tree based on partial small-subunit ribosomal DNA (SSU rDNA) sequences, T. taimyr branches together with the two other known species of Toxisarcon within the clade C of monothalamous foraminifera.

Description: Submarine slope failures of various types and sizes are common along the tectonic and seismically active Ligurian margin, northwestern Mediterranean Sea, primarily because of seismicity up to ~M6, rapid sediment deposition in the Var fluvial system, and steepness of the continental slope (average 11°). We present geophysical, sedimentological and geotechnical results of two distinct slides in water depth 〉1,500 m: one located on the flank of the Upper Var Valley called Western Slide (WS), another located at the base of continental slope called Eastern Slide (ES). WS is a superficial slide characterized by a slope angle of ~4.6° and shallow scar (~30 m) whereas ES is a deep-seated slide with a lower slope angle (~3°) and deep scar (~100 m). Both areas mainly comprise clayey silt with intermediate plasticity, low water content (30–75 %) and underconsolidation to strong overconsolidation. Upslope undeformed sediments have low undrained shear strength (0–20 kPa) increasing gradually with depth, whereas an abrupt increase in strength up to 200 kPa occurs at a depth of ~3.6 m in the headwall of WS and ~1.0 m in the headwall of ES. These boundaries are interpreted as earlier failure planes that have been covered by hemipelagite or talus from upslope after landslide emplacement. Infinite slope stability analyses indicate both sites are stable under static conditions; however, slope failure may occur in undrained earthquake condition. Peak earthquake acceleration from 0.09 g on WS and 0.12 g on ES, i.e. M5–5.3 earthquakes on the spot, would be required to induce slope instability. Different failure styles include rapid sedimentation on steep canyon flanks with undercutting causing superficial slides in the west and an earthquake on the adjacent Marcel fault to trigger a deep-seated slide in the east.

Description: This Encyclopedia comprises the current knowledge in marine geosciences whereby not only basic but also applied and technical sciences are covered. Through this concept a broad scale of users in the field of marine sciences and techniques is addressed, from students and scholars in academia to engineers and decision makers in industry and politics. Globally growing demand of energy and mineral resources, reliable future projection of climate processes and the protection of coasts to mitigate the threats of disasters and hazards require a comprehensive understanding of the structure, ongoing processes and genesis of the marine geosphere. Beyond the “classical” research fields in marine geology in current time more general concepts have been evolved integrating marine geophysics, hydrography, marine biology, climatology and ecology. As an umbrella the term “marine geosciences” has been broadly accepted for this new complex field of research and the solutions of practical tasks in the marine realm.

Description: Oceanic eddies having scales from several hundred meters to several hundred kilometers are ubiquitous phenomena in the World’s ocean. This became evident only after they could be observed from satellites and space shuttles. Here we present several images taken in different spectral bands which show signatures of eddies of different spatial scales in sea areas around Africa. In particular, we present a series of satellite images showing the propagation of a small-scale cyclonic (cold) eddy generated at Cap-Vert at the coast of Senegal into the open ocean. We show that this small-scale eddy transported nutrients from the Senegal upwelling region westward into the oligotrophic North Atlantic thus giving rise to enhanced chlorophyll-a concentration there. Since eddies are also areas of high fish population, knowledge of their position and properties is of great importance for fishery.

Description: The main migrations of the Polar front (PF) during the last 300 ka were identified using planktic foraminiferal census data and derived from them sea surface paleotemperature (SST) estimates in two synchronized AMK-4438 and M23414 cores recovered directly beneath the main stream of the North Atlantic Current (NAC) south of Iceland. During the summer seasons, the cold waters adjacent to the PF did not reach the studied sites. These waters occurred here only during the winter seasons of MIS 2, 6, and 8. The northern part of the study area was influenced by the arctic waters more often than its southern part. During MIS 8 and 6 isotherms in the North Atlantic had mainly the subzonal orientation, while during MIS 2-4 they had the submeridional orientation. During the interglacials, the PF was located northward and westward from the study area. During MIS 7, the front was presumably situated closer to the study area in comparison with its modern position, and the isotherms were oriented mainly subzonal. For the MIS 5e period, we observed the most distant retreat of PF from the investigated area in the western and northwestern direction in relation to the anomalous deflection of the NAC to the north-west (intensification of the Irminger current) and the predominance of the submeridional orientation of the isotherms in the study area. During MIS 1, as well as MIS 7, the isotherms in the study area had mainly the subzonal orientation.

Description: Three bottom sediment cores (140–190 cm long) taken from Isfjorden, West Spitsbergen, were analysed for pollen and spores with the main aim of elucidating the local pattern of pollen and spore succession in order to establish age control and define the stratigraphy of marine sediments. Isfjorden bottom sediments consist of greyish-green silty pelite with gruss, detritus, and pebble inclusions. The upper 25 cm are water-saturated and nonplastic. In spite of extremely low concentrations, and the predominance of reworked pre-Quaternary microfossils, the marine pollen spectra appear quite similar to those known from radiocarbon-dated lake sediments and peat exposures on the coasts of neighbouring Billefjorden, Van Mijenfjorden, and Hornsundfjorden, provided that long-distance transported pollen of conifers, tree birches, and spores of ferns are eliminated from marine pollen spectra compositions. The correlation of pollen zones (PZ) established in fjord sediments with those known from peat and lake sections enables the pollen-based stratigraphy of Isfjorden bottom sediments to be established and further reconstruction to be made of the major stages of the late Holocene terrestrial vegetation history of West Spitsbergen. The oldest pollen records date back to about 2.8–3 ka. They characterize the lowermost silty pelite layer (intervals 180–150 cm in core 11 and 190–60 cm in core 14 from the southwestern part of the fjord). At this time, moss–cereal–sedge fens and heather bogs in the coastal areas coexisted with rocky tundra vegetation at higher elevations. A marked increase in the content of Salix sp., Betula sect. Nanae-type, and Ericales pollen is recorded in the upper part of the pelite layer in cores 11 and 14. Similar spectra dominate core 9 from the northeastern inner part of the fjord. The percentage of green moss spores is extremely low. This type of spectra is suggestive of a warmer-than-present climate in West Spitsbergen. The upper water-saturated layer of all three cores contains pollen assemblages that are very similar to those identified in the Isfjorden surface sediment samples. Therefore, they have been likely accumulated during the last 2000 years. These uppermost pollen assemblages show a sharp increase in sedge pollen. This suggests the expansion of coastal fens, which can be attributed to an increase in the amount of precipitation. Extremely low pollen concentrations in Isfjorden bottom sediments possibly reflect very high accumulation rates during the time of silty pelite layer sedimentation.

Description: Lake Mogilnoe (Kildin Island, the Barents Sea) is a marine stratified lake, a refuge for landlocked populations of marine organisms. Unlike other known marine lakes from polar areas, which communicate with the sea by water percolation at the surface, Mogilnoe has a subterranean connection with the sea like tropical and subtropical anchialine lakes. Similarly to some other marine lakes, Mogilnoe has traditionally been considered to be biologically isolated from the sea and subject to little change. We review the current status of the physical features, zooplankton and benthos of Mogilnoe and trace changes that have occurred in the lake since the start of observations in 1894. The anaerobic bottom water layer has expanded by 100 %, while the upper freshwater layer has diminished by 40 %. The species diversity of zooplankton and macrobenthos has halved. The occurrence of Atlantic cod likens Mogilnoe to some other Arctic marine lakes while the presence of large flocks of sea anemones, scyphomedusae and suberitid sponges makes it similar to tropical anchialine lakes. Lake Mogilnoe is not entirely biologically isolated; accidental introduction of species from the sea does occur. We argue that the idealised model of an isolated steady-state ecosystem can be applied to a marine lake with caution. A model of fluctuating abiotic environment and partial biological isolation portrays the real situation better.

Description: Two sediment cores retrieved from the southern Lomonosov Ridge (LR) in 2007 (core ALR07-26C from the top of the ridge, water depth 1359 m, and core ALR07-15C from the base of Geophysicists’ Spur, water depth 2500 m) were investigated for lithology (wt % 〉 63 μm, terrigenous lithic grains 〉500 μm) and microfossils. Prominent peaks of coarse-grained material in ALR07-26C represented largely by quartz and clastic rocks are regarded as inputs of ice and, especially, iceberg-rafted debris (IRD) of Eurasian origin. In accordance with previously obtained evidence from age-constrained cores from the central LR, the highest peak 4 is correlated with the MIS 6–5 boundary and the disintegration of the Saalian ice sheet. The three younger IRD peaks are provisionally correlated with the MIS 5–4, MIS 4–3, and MIS 2–1 boundaries, respectively. Small peaks of coarse-grained material in ALR07-15C dominated by various rocks in contrast represent local material transported by downslope slides mixed with some IRD. No calcareous microfossils occur in the cores, but only agglutinated benthic foraminifers are found. In ALR07-26C, they correlate with IRD-rich layers, which correspond to glacial terminations with more open-sea ice conditions and, probably, higher productivity in the sea-ice marginal zone. The Cyclammina-dominated assemblage in ALR07-26C below IRD peak 4 supports the proposed age estimate for this peak (MIS 6–5), as similar foraminiferal assemblages in other LR cores are recorded in sediments of MIS 7–9 and older. Younger assemblages show a transition from a Recurvoides-dominated assemblage in the early Late Pleistocene to a more “oligotrophic” recent assemblage with a predominance of Reophax and Rhabdammina.

Description: Mediterranean Outflow Water (MOW) is thought to be a key contributor to the strength and stability of Atlantic Meridional Overturning Circulation (AMOC), but the future of Mediterranean-Atlantic water exchange is uncertain. It is chiefly dependent on the difference between Mediterranean and Atlantic temperature and salinity characteristics, and as a semi-enclosed basin, the Mediterranean is particularly vulnerable to future changes in climate and water usage. Certainly, there is strong geologic evidence that the Mediterranean underwent dramatic salinity and sea-level fluctuations in the past. Here, we use a fully coupled atmosphere–ocean General Circulation Model to examine the impact of changes in Mediterranean-Atlantic exchange on global ocean circulation and climate. Our results suggest that MOW strengthens and possibly stabilises the AMOC not through any contribution towards NADW formation, but by delivering relatively warm, saline water to southbound Atlantic currents below 800 m. However, we find almost no climate signal associated with changes in Mediterranean-Atlantic flow strength. Mediterranean salinity, on the other hand, controls MOW buoyancy in the Atlantic and therefore affects its interaction with the shallow-intermediate circulation patterns that govern surface climate. Changing Mediterranean salinity by a factor of two reorganises shallow North Atlantic circulation, resulting in regional climate anomalies in the North Atlantic, Labrador and Greenland-Iceland-Norwegian Seas of ±4 °C or more. Although such major variations in salinity are believed to have occurred in the past, they are unlikely to occur in the near future. However, our work does suggest that changes in the Mediterranean’s hydrological balance can impact global-scale climate.

Description: Seafloormethane emission from the Quepos Slide on the submarine segment of the Costa Rica fore-arc margin was estimated by extrapolating flux measurements from individual seeps to the total area covered by bacterial mats. This approach is based on the combination of detailed mapping to determine the abundance of seeps and the application of a numerical model to estimate the amount of benthic methane fluxes. Model results suggest that the majority of the studied seeps transport rather limited amount of methane (on average: *177 lmol cm-2 a-1) into the water column due to moderate upward advection, allowing for intense anaerobic oxidation of methane (AOM; on average: 53 % of the methane flux is consumed). Depth-integrated AOM rates (56–1,538 lmol CH4 cm-2 a-1) are comparable with values reported from other active seep sites. The overall amount of dissolved methane released into the water column from the entire area covered by bacterial mats on the Quepos Slide is estimated to be about 0.28 9 106 mol a-1. This conservative estimate which relies on rather accurate determinations of seafloor methane fluxes emphasizes the potential importance of submarine slides as sites of natural methane seepage; however, at present the global extent of methane seepage from submarine slides is largely unknown.

Description: The surface sediments of two mud mounds (‘‘Mound 11’’ and ‘‘Mound 12’’) offshore southwest Costa Rica contain abundant authigenic carbonate concretions dominated by high-Mg calcite (14–20 mol-% MgCO3). Pore fluid geochemical profiles (sulfate, sulfide, methane, alkalinity, Ca and Mg) indicate recent carbonate precipitation within the zone of anaerobic oxidation of methane (AOM) at variable depths. The current location of the authigenic carbonate concretions is, however, not related to the present location of the AOM zone, suggesting mineral precipitation under past geochemical conditions as well as changes in the flow rates of upward migrating fluids. Stable oxygen and carbon isotope analysis of authigenic carbonate concretions yielded d18Ocarbonate values ranging between 34.0 and 37.7 % Vienna standard mean ocean water (VSMOW) and d13Ccarbonate values from -52.2 to -14.2 % Vienna Pee Dee belemnite (VPDB). Assuming that no temperature changes occurred during mineral formation, the authigenic carbonate concretions have been formed at in situ temperature of 4–5 °C. The d18Ocarbonate values suggest mineral formation from seawater-derived pore fluid (d18Oporefluid = 0 % VSMOW) for Mound 12 carbonate concretions but also the presence of an emanating diagenetic fluid (d18Oporefluid &5 %) in Mound 11. A positive correlation between d13Ccarbonate and d18Ocarbonate is observed, indicating the admixing of two different sources of dissolved carbon and oxygen in the sediments of the two mounds. The carbon of these sources are (1) marine bicarbonate (d13Cporefluid &0 %) and (2) bicarbonate which formed during the AOM (d13Cporefluid &-70 %). Furthermore, the d18Oporefluid composition, with values up to ?4.7 % Vienna standard mean ocean water (VSMOW), is interpreted to be affected by the presence of emanating, freshened and boronenriched fluids. Earlier, it has been shown that the origin of 18O-enriched fluids are deep diagenetic processes as it was indicated by the presence of methane with thermogenic signature (d13CCH4 = -38 %). A combination of present geochemical data with geophysical observations indicates that Mounds 11 and 12 represent a single fluid system interconnected by deep-seated fault(s).

Description: Larval fish growth and survival depends not only on prey quantity, but also on prey quality. To investigate effects of prey fatty acid concentration on larval herring growth, we collected different prey organisms and larval herring (Clupea harengus L.) in the Kiel Canal during the spring season of 2009. Along with biotic background data, we analysed fatty acids both in prey organisms and in the larvae and used biochemically derived growth rates of the larvae as the response variable. Larval herring reached their highest RNA/DNA derived growth rates only at high docosahexaenoic acid (DHA) concentration. When the ratio of copepodids to lesser quality cirriped nauplii was low, larval growth and larval DHA concentration were both significantly negatively affected. This was true even as prey abundance was increasing. This finding indicates that even in mixed, natural feeding conditions, growth variations are associated with DHA availability in larval fish.

Description: Understanding and quantifying ocean–atmosphere exchanges of the long-lived greenhouse gases carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) are important for understanding the global biogeochemical cycles of carbon and nitrogen in the context of ongoing global climate change. In this chapter we summarise our current state of knowledge regarding the oceanic distributions, formation and consumption pathways, and oceanic uptake and emissions of CO2, N2O and CH4, with a particular emphasis on the upper ocean. We specifically consider the role of the ocean in regulating the tropospheric content of these important radiative gases in a world in which their tropospheric content is rapidly increasing and estimate the impact of global change on their present and future oceanic uptake and/or emission. Finally, we evaluate the various uncertainties associated with the most commonly used methods for estimating uptake and emission and identify future research needs.

Description: In analysis of climate variability or change it is often of interest how the spatial structure in modes of variability in two datasets differ from each other, e.g. between past and future climate or between models and observations. Often such analysis is based on Empirical Orthogonal Function (EOF) analysis or other simple indices of large-scale spatial structures. The present analysis lays out a concept on how two datasets of multivariate climate variability can be compared against each other on basis of EOF analysis and how the differences in the multivariate spatial structure between the two datasets can be quantified in terms of explained variance in the leading spatial patterns. It is also illustrated how the patterns of largest differences between the two datasets can be defined and interpreted. We illustrate this method on the basis of several well-defined artificial examples and by comparing our approach with examples of climate change studies from the literature. These literature examples include analysis of changes in the modes of variability under climate change for the sea level pressure (SLP) of the North Atlantic and Europe, the SLP of the Southern Hemisphere, the surface temperature of the Northern Hemisphere, the sea surface temperature of the North Pacific and for precipitation in the tropical Indo-Pacific.

Description: Recent studies show that mid-latitude SST variations over the Kuroshio-Oyashio Extension influence the atmospheric circulation. However, the impact of variations in SST in the Gulf Stream region on the atmosphere has been less studied. Understanding the atmospheric response to such variability can improve the climate predictability in the North Atlantic Sector. Here we use a relatively high resolution (∼1°) Atmospheric General Circulation Model to investigate the mechanisms linking observed 5-year low-pass filtered SST variability in the Gulf Stream region and atmospheric variability, with focus on precipitation. Our results indicate that up to 70 % of local convective precipitation variability on these timescales can be explained by Gulf Stream SST variations. In this region, SST and convective precipitation are strongly correlated in both summer (r = 0.73) and winter (r = 0.55). A sensitivity experiment with a prescribed local warm SST anomaly in the Gulf Stream region confirms that local SST drives most of the precipitation variability over the Gulf Stream. Increased evaporation connected to the anomalous warm SST plays a crucial role in both seasons. In summer there is an enhanced local SLP minimum, a concentrated band of low level convergence, deep upward motion and enhanced precipitation. In winter we also get enhanced precipitation, but a direct connection to deep vertical upward motion is not found. Nearly all of the anomalous precipitation in winter is connected to passing atmospheric fronts. In summer the connection between precipitation and atmospheric fronts is weaker, but still important.

Description: Subduction zones of continental, transitional, and oceanic settings, relative to the nature of the overriding plate, are compared in terms of trace element compositions of mafic to intermediate arc rocks, in order to evaluate the relationship between subduction parameters and the presence of subduction fluids. The continental Chilean Southern Volcanic Zone (SVZ) and the transitional to oceanic Central American Volcanic Arc (CAVA) show increasing degrees of melting with increasing involvement of slab fluids, as is typical for hydrous flux melting beneath arc volcanoes. At the SVZ, the central segment with the thinnest continental crust/lithosphere erupted the highest-degree melts from the most depleted sources, similar to the oceanic-like Nicaraguan segment of the CAVA. The northern part of the SVZ, located on the thickest continental crust/lithosphere, exhibits features more similar to Costa Rica situated on the Caribbean Large Igneous Province, with lower degrees of melting from more enriched source materials. The composition of the slab fluids is characteristic for each arc system, with a particularly pronounced enrichment in Pb at the SVZ and in Ba at the CAVA. A direct compositional relationship between the arc rocks and the corresponding marine sediments that are subducted at the trenches clearly shows that the compositional signature of the lavas erupted in the different arcs carries an inherited signal from the subducted sediments.

Description: The variability of the East Asian summer monsoon (EASM) is studied using a partially coupled climate model (PCCM) in which the ocean component is driven by observed monthly mean wind stress anomalies added to the monthly mean wind stress climatology from a fully coupled control run. The thermodynamic coupling between the atmospheric and oceanic components is the same as in the fully coupled model and, in particular, sea surface temperature (SST) is a fully prognostic variable. The results show that the PCCM simulates the observed SST variability remarkably well in the tropical and North Pacific and Indian Oceans. Analysis of the rainfall-SST and rainfall-SST tendency correlation shows that the PCCM exhibits local air-sea coupling as in the fully coupled model and closer to what is seen in observations than is found in an atmospheric model driven by observed SST. An ensemble of experiments using the PCCM is analysed using a multivariate EOF analysis to identify the two major modes of variability of the EASM. The PCCM simulates the spatial pattern of the first two modes seen in the ERA40 reanalysis as well as part of the variability of the first principal component (correlation up to 0.5 for the model ensemble mean). Different from previous studies, the link between the first principal component and ENSO in the previous winter is found to be robust for the ensemble mean throughout the whole period of 1958–2001. Individual ensemble members nevertheless show the breakdown in the relationship before the 1980’s as seen in the observations.

Description: Melt inclusions in olivine Fo83–72 from tephras of 1867, 1971 and 1992 eruptions of Cerro Negro volcano represent a series of basaltic to andesitic melts of narrow range of MgO (5.6–8 wt %) formed by ~46 wt % fractional crystallization of olivine (~6 wt %), plagioclase (~27 wt %), pyroxene (~13 wt %) and magnetite (〈1 wt %) from primitive basaltic melt (average SiO2 = 49 wt %, MgO = 7.6 wt %, H2O = 6 wt %) as it ascended to the surface from the depth of about 14 km. The crystallization occurred at increasing liquidus temperature from 1,050 to 1,090 °C in the pressure range from 400 to 50 MPa and was induced by release of mixed H2O–CO2 fluid from the melt at decreasing pressure. Matrix glass compositions fall at the high-Si end of the melt inclusion trend and represent the final stage of melt crystallization during and after eruption. The bulk compositions of erupted Cerro Negro magmas (tephras and lavas) range from high- to low-MgO (3–10 wt %) basalts, which form a compositional array crossing the trend of melt inclusions so that virtually no rock from Cerro Negro has composition akin to true melt represented by the inclusions. The variations of the bulk magma (rocks) and melt (melt inclusions) compositions can be generated in a dyke connecting a deep primitive magma reservoir with the Cerro Negro edifice. While the melt inclusions represent the compositional trend of instantaneous melts along the magma pathway at decreasing pressure and H2O content, occurrence of low-Mg to high-Mg basalts reflects the process of phenocryst re-distribution in progressively evolving melt. The crystallization scenario is anticipated to operate everywhere in dykes feeding basaltic volcanoes and can explain the predominance of plagioclase-rich high-Al basalts in island arc as well as typical compositional variations of magmas during single eruptions.

Description: Transition from subduction of normal to thickened oceanic crust occurs in the central portion of the Costa Rican margin, where large interplate earthquakes (M * 7) and abundant interseismic seismicity have been associated with subduction of bathymetric highs. We relocated *1,300 earthquakes recorded for 6 months by a combined on- and offshore seismological network using probabilistic earthquake relocation in a 3D P-wave velocity model. Most of the seismicity originated at the seismogenic zone of the plate boundary, appearing as an 18° dipping, planar cluster from 15 to 25–30 km depth, beneath the continental shelf. Several reverse focal mechanisms were resolved within the cluster. The upper limit of this interseismic interplate seismicity seems to be controlled primarily by the overlying-plate thickness and coherency, which in turn is governed by the erosional processes and fluid release and escape at temperatures lower than *100 to 120° C along the plate boundary. The downdip limit of the stick–slip behaviour collocates with relative low temperatures of *150 to 200° C, suggesting that it is controlled by serpentinization of the mantle wedge. The distribution of the interseismic interplate seismicity is locally modified by the presence of subducted seamounts at different depths. Unlike in northern Costa Rica, rupture of large earthquakes in the last two decades seems to coincide with the area defined by the interseismic interplate seismicity.

Description: Llaima and Villarrica are two of the most active volcanoes in the Chilean Southern Volcanic Zone and presently show contrasting types of activity. Llaima is a closed vent edifice with fumarolic activity, while Villarrica has an open vent with a lava lake, continuous degassing and tremor activity. This study is focused on characterizing the relationships between volcanic and seismic activity in the months before and after the 2010 M8.8 Maule earthquake, which was located in NNW direction from the volcanoes. Time series for tremors, long-period and volcano-tectonic events were obtained from the catalogue of the Volcanic Observatory of the Southern Andes (OVDAS) and from the SFB 574 temporary volcanic network. An increase in the amount of tremor activity, long-period events and degassing rates was observed at Villarrica weeks before the mainshock and continued at a high level also after it. This increase in activity is interpreted to be caused by enhanced magma influx at depth and may be unrelated to the Maule event. In Llaima, an increase in the volcano-tectonic activity was observed directly after the earthquake. The simultaneous post-earthquake activity at both volcanoes is consistent with a structural adjustment response. Since this enhanced activity lasted for more than a year, we suggest that it is related to a medium-term change in the static stress. Thus, the Maule earthquake may have affected both volcanoes, but did not trigger eruptions, from which we assume that none of the volcanoes were in a critical state.

Description: Here we present the first systematic investigation of volatile geochemistry along the Southern Volcanic Zone (SVZ) of Chile. Holocene olivine-hosted melt inclusions in the most mafic tephras sampled from 16 volcanoes along the volcanic front of the SVZ between 33°S and 43°S were analysed for pre-eruptive sulphur, chlorine, and major element contents. These results are combined with trace element compositions of the host whole rocks. The highest fractionation-corrected gas contents occur in the least-degassed melt inclusions from small monogenetic cones of Los Hornitos, Cabeza de Vaca, and Apagado from both the transitional and the southern-central SVZ, reaching ~3,000 μg/g S and 1,400 μg/g Cl, while the lowest abundances of ~1,100 μg/g S and ~600 μg/g Cl were found in the central SVZ at Volcán Lonquimay, Volcán Llaima, and Volcán Villarrica. Chlorine co-varies with trace element indicators for the degree of melting and/or source enrichment, such that the lowest Cl contents are found in high-degree melts from the most depleted mantle sources. The size of the volcanic edifices correlates inversely with Cl abundances in the melt. This could reflect more extensive degassing during ascent through the complex magma plumbing systems beneath the stratovolcanoes or greater dilution during larger degrees of melting of more depleted sources, or a combination of these factors. Compared to other subduction zones, the SVZ melt inclusions exhibit Cl and S abundances in the same range as most of those from the Central American and those from the Marianas arcs.

Description: There is evidence that the observed changes in winter North Atlantic Oscillation (NAO) drive a significant portion of Atlantic Multi Decadal Variability (AMV). However, whether the observed decadal NAO changes can be forced by the ocean is controversial. There is also evidence that artificially imposed multi-decadal stratospheric changes can impact the troposphere in winter. But the origins of such stratospheric changes are still unclear, especially in early to mid winter, where the radiative ozone-impact is negligible. Here we show, through observational analysis and atmospheric model experiments, that large-scale Atlantic warming associated with AMV drives high-latitude precursory stratospheric warming in early to mid winter that propagates downward resulting in a negative tropospheric NAO in late winter. The mechanism involves stratosphere/troposphere dynamical coupling, and can be simulated to a large extent, but only with a stratosphere resolving model (i.e., high-top). Further analysis shows that this precursory stratospheric response can be explained by the shift of the daily extremes toward more major stratospheric warming events. This shift cannot be simulated with the atmospheric (low-top) model configuration that poorly resolves the stratosphere and implements a sponge layer in upper model levels. While the potential role of the stratosphere in multi-decadal NAO and Atlantic meridional overturning circulation changes has been recognised, our results show that the stratosphere is an essential element of extra-tropical atmospheric response to ocean variability. Our findings suggest that the use of stratosphere resolving models should improve the simulation, prediction, and projection of extra-tropical climate, and lead to a better understanding of natural and anthropogenic climate change.

Description: The continental shelf and slope of southern Central Chile have been subject to a number of international as well as Chilean research campaigns over the last 30 years. This work summarizes the geologic setting of the southern Central Chilean Continental shelf (33°S–43°S) using recently published geophysical, seismological, sedimentological and bio-geochemical data. Additionally, unpublished data such as reflection seismic profiles, swath bathymetry and observations on biota that allow further insights into the evolution of this continental platform are integrated. The outcome is an overview of the current knowledge about the geology of the southern Central Chilean shelf and upper slope. We observe both patches of reduced as well as high recent sedimentation on the shelf and upper slope, due to local redistribution of fluvial input, mainly governed by bottom currents and submarine canyons and highly productive upwelling zones. Shelf basins show highly variable thickness of Oligocene-Quaternary sedimentary units that are dissected by the marine continuations of upper plate faults known from land. Seismic velocity studies indicate that a paleo-accretionary complex that is sandwiched between the present, relatively small active accretionary prism and the continental crust forms the bulk of the continental margin of southern Central Chile.

Description: Methane (CH4) concentrations and CH4 stable carbon isotopic composition (d13CCH4 ) were investigated in the water column within Jaco Scar. It is one of several scars formed by massive slides resulting from the subduction of seamounts offshore Costa Rica, a process that can open up structural and stratigraphical pathways for migrating CH4. The release of large amounts of CH4 into the adjacent water column was discovered at the outcropping lowermost sedimentary sequence of the hanging wall in the northwest corner of Jaco Scar, where concentrations reached up to 1,500 nmol L-1. There CH4-rich fluids seeping from the sedimentary sequence stimulate both growth and activity of a dense chemosynthetic community. Additional point sources supplying CH4 at lower concentrations were identified in density layers above and below the main plume from light carbon isotope ratios. The injected CH4 is most likely a mixture of microbial and thermogenic CH4 as suggested by d13CCH4 values between -50 and -62 % Vienna Pee Dee Belemnite. This CH4 spreads along isopycnal surfaces throughout the whole area of the scar, and the concentrations decrease due to mixing with ocean water and microbial oxidation. The supply of CH4 appears to be persistent as repeatedly high CH4 concentrations were found within the scar over 6 years. The maximum CH4 concentration and average excess CH4 concentration at Jaco Scar indicate that CH4 seepage from scars might be as significant as seepage from other tectonic structures in the marine realm. Hence, taking into account the global abundance of scars, such structures might constitute a substantial, hitherto unconsidered contribution to natural CH4 sources at the seafloor.

Description: In a recent study it was illustrated that the El Nino Southern Oscillation (ENSO) mode can exist in the absence of any ocean dynamics. This oscillating mode exists just due to the interaction between atmospheric heat fluxes and ocean heat capacity. The primary purpose of this study is to further explore these atmospheric Slab Ocean ENSO dynamics and therefore the role of positive atmospheric feedbacks in model simulations and observations. The positive solar radiation feedback to sea surface temperature (SST), due to reduced cloud cover for anomalous warm SSTs, is the main positive feedback in the Slab Ocean El Nino dynamics. The strength of this positive cloud feedback is strongly related to the strength of the equatorial cold tongue. The combination of positive latent and sensible heat fluxes to the west and negative ones to the east of positive anomalies leads to the westward propagation of the SST anomalies, which allows for oscillating behavior with a preferred period of 6-7 years. Several indications are found that parts of these dynamics are indeed observed and simulated in other atmospheric or coupled general circulation models (AGCMs or CGCMs). The CMIP3 AGCM-slab ensemble of 13 different AGCM simulations shows unstable ocean-atmosphere interactions along the equatorial Pacific related to stronger cold tongues. In observations and in the CMIP3 and CMIP5 CGCM model ensemble the strength and sign of the cloud feedback is a function of the strength of the cold tongue. In summary, this indicates that the Slab Ocean El Nino dynamics are indeed a characteristic of the equatorial Pacific climate that is only dominant or significantly contributing to the ENSO dynamics if the SST cold tongue is sufficiently strong. In the observations this is only the case during strong La Nina conditions. The presence of the Slab Ocean ENSO atmospheric feedbacks in observations and CGCM model simulations implies that the family of physical ENSO modes does have another member, which is entirely driven by atmospheric processes and does not need to have the same spatial pattern nor the same time scales as the main ENSO dynamics.

Description: Sediments of Lake Van, Turkey, preserve one of the most complete records of continental climate change in the Near East since the Middle Pleistocene. We used seismic reflection profiles to infer past changes in lake level and discuss potential causes related to changes in climate, volcanism, and regional tectonics since the formation of the lake ca. 600 ka ago. Lake Van's water level ranged by as much as 600 m during the past 600 ka. Five major lowstands occurred, at 600, 365-340, 290-230, 150-130 and 30-14 ka. During Stage A, between about 600 and 230 ka, lake level changed dramatically, by hundreds of meters, but phases of low and high stands were separated by long time intervals. Changes in the lake level were more frequent during the past 230 ka, but less dramatic, on the order of a few tens of meters. We identified period B1 as a time of stepwise transgressions between 230 and 150 ka, followed by a short regression between ca. 150 and 130 ka. Lake level rose stepwise during period B2, until 30 ka. During the past 30 ka, a regression and a final transgression occurred, each lasting about 15 ka. The major lowstand periods in Lake Van occurred during glacial periods, suggesting climatic control on water level changes (i.e. greatly reduced precipitation led to lower lake levels). Although climate forcing was the dominant cause for dramatic water level changes in Lake Van, volcanic and tectonic forcing factors may have contributed as well. For instance, the number of distinct tephra layers, some several meters thick, increases dramatically in the uppermost 100 m of the sediment record (i.e. the past 230 ka), an interval that coincides largely with low-magnitude lake level fluctuations. Tectonic activity, highlighted by extensional and/or compressional faults across the basin margins, probably also affected the lake level of Lake Van in the past.

Description: In this paper, we constrain the input and output fluxes of H2O, Cl and S into the southern-central Chilean subduction zone (31°S–46°S). We determine the input flux by calculating the amounts of water, chlorine and sulfur that are carried into the subduction zone in subducted sediments, igneous crust and hydrated lithospheric mantle. The applied models take into account that latitudinal variations in the subducting Nazca plate impact the crustal porosity and the degree of upper mantle serpentinization and thus water storage in the crust and mantle. In another step, we constrain the output fluxes of the subduction zone both to the subcontinental lithospheric mantle and to the atmosphere–geosphere–ocean by the combined use of gas flux determinations at the volcanic arc, volume calculations of volcanic rocks and the combination of mineralogical and geothermal models of the subduction zone. The calculations indicate that about 68 Tg/m/Ma of water enters the subduction zone, as averaged over its total length of 1,480 km. The volcanic output on the other hand accounts for 2 Tg/m/Ma or 3 % of that input. We presume that a large fraction of the volatiles that are captured within the subducting sediments (which accounts for roughly one-third of the input) are cycled back into the ocean through the forearc. This assumption is however questioned by the present lack of evidence for major venting systems of the submarine forearc. The largest part of the water that is carried into the subduction zone in the crust and hydrated mantle (accounting for two-thirds of the input) appears to be transported beyond the volcanic arc.

Description: After more than a decade of multidisciplinary studies of the Central American subduction zone mainly in the framework of two large research programmes, the US MARGINS program and the German Collaborative Research Center SFB 574, we here review and interpret the data pertinent to quantify the cycling of mineral-bound volatiles (H2O, CO2, Cl, S) through this subduction system. For input-flux calculations, we divide the Middle America Trench into four segments differing in convergence rate and slab lithological profiles, use the latest evidence for mantle serpentinization of the Cocos slab approaching the trench, and for the first time explicitly include subduction erosion of forearc basement. Resulting input fluxes are 40–62 (53) Tg/Ma/m H2O, 7.8–11.4 (9.3) Tg/Ma/m CO2, 1.3–1.9 (1.6) Tg/Ma/m Cl, and 1.3–2.1 (1.6) Tg/Ma/m S (bracketed are mean values for entire trench length). Output by cold seeps on the forearc amounts to 0.625–1.25 Tg/Ma/m H2O partly derived from the slab sediments as determined by geochemical analyses of fluids and carbonates. The major volatile output occurs at the Central American volcanic arc that is divided into ten arc segments by dextral strike-slip tectonics. Based on volcanic edifice and widespread tephra volumes as well as calculated parental magma masses needed to form observed evolved compositions, we determine long-term (105 years) average magma and K2O fluxes for each of the ten segments as 32–242 (106) Tg/Ma/m magma and 0.28–2.91 (1.38) Tg/Ma/m K2O (bracketed are mean values for entire Central American volcanic arc length). Volatile/K2O concentration ratios derived from melt inclusion analyses and petrologic modelling then allow to calculate volatile fluxes as 1.02–14.3 (6.2) Tg/Ma/m H2O, 0.02–0.45 (0.17) Tg/Ma/m CO2, and 0.07–0.34 (0.22) Tg/Ma/m Cl. The same approach yields long-term sulfur fluxes of 0.12–1.08 (0.54) Tg/Ma/m while present-day open-vent SO2-flux monitoring yields 0.06–2.37 (0.83) Tg/Ma/m S. Input–output comparisons show that the arc water fluxes only account for up to 40 % of the input even if we include an “invisible” plutonic component constrained by crustal growth. With 20–30 % of the H2O input transferred into the deeper mantle as suggested by petrologic modeling, there remains a deficiency of, say, 30–40 % in the water budget. At least some of this water is transferred into two upper-plate regions of low seismic velocity and electrical resistivity whose sizes vary along arc: one region widely envelopes the melt ascent paths from slab top to arc and the other extends obliquely from the slab below the forearc to below the arc. Whether these reservoirs are transient or steady remains unknown.

Description: Estuarine turbidity maxima (ETM) play an impor- tant role in zooplankton and larval fish productivity in many estuaries. Yet in many of these systems, little is known about the food web that supports this secondary production. To see if phytoplankton have the potential to be a component of the ETM food web in the Chesapeake Bay estuary a series of cruises were carried out to determine the biomass distribution and floral composition of phytoplankton in and around the ETM during the winter and spring using fluorometry, high- performance liquid chromatography (HPLC), and microscopy. Two distinct phytoplankton communities were observed along the salinity gradient. In lower salinity waters, biomass was low and the community was composed mostly of diatoms, while in more saline waters biomass was high and the community was composed mostly of mixotrophic dinoflagellates, which were often concentrated in a thin layer below the pycnocline. Phytoplankton biomass was always low in the ETM, but high concentrations of phytoplankton pigment degradation products and cellular remains were often observed suggesting that this was an area of high phytoplankton mortality and/or an area where phytoplankton derived particulate organic matter was being trapped. These results, along with a box model analysis, suggest that under certain hydrodynamic conditions phyto- plankton derived organic matter can be trapped in ETM and potentially play a role in fueling secondary production.

Description: Silvetia babingtonii is a potentially economic brown alga for sources of food and high-value added utilization. So far, sporeling nursery and field cultivation has not been successful. The lack of knowledge on development and life cycle of this alga hinder the development of techniques for the sporeings and cultivation. In this study, internal structure of oogonium and antherium of S. babingtonii was observed with hematoxylin and eosin staining and through microscope. Meanwhile, early development from zygotes to juvenile sporelings was studied at 20 degrees C under 60-100 mu mol photons m(-2) s(-1). Zygotes germinated and divided into thallus and rhizoid cells. The larger thallus cells further divided and developed into juvenile sporelings; while the smaller rhizoid cells divided and elongated into rhizoid hairs. These findings documented the life cycle of S. babingtonii and provided fundamental knowledge for sporeling nursery in the near future.

Description: Since the discovery of the green sulfur bacteria and the first description by Larsen (1952), this group of bacteria has gained much interest because of a number of highly interesting features. These include the unique structures of the photosynthetic apparatus and the presence of small organelles, the chlorosomes, which act as light-harvesting antenna. Chlorosomes are very powerful light receptors that can capture minute amounts of light and enable the green sulfur bacteria to perform photosynthesis and to grow at very low-light intensities. This has important ecological consequences, because the efficient light harvesting determines the ecological niche of these bacteria at the lowermost part of stratified environments, where the least of light is available. Furthermore, the strict dependency on photosynthesis to provide energy for growth and the obligate phototrophy of the green sulfur bacteria together with their characteristic sulfur metabolism has provoked much interest in their physiology, ecology, and genomics. The oxidation of sulfide as the outmost important photosynthetic electron donor of the green sulfur bacteria involves the deposition of elemental sulfur globules outside the cells and separates the process of sulfide oxidation to sulfate clearly into two steps. In the phylogenetic-based taxonomy, the green sulfur bacteria are treated as family Chlorobiaceae with the genera Chlorobium, Chlorobaculum, Prosthecochloris, and Chloroherpeton.

Description: The Kiloniellaceae family is represented currently by a single genus Kiloniella with the species Kiloniella laminariae as type species. Kiloniella laminariae was isolated from the marine macroalga Saccharina latissima (former Laminaria saccharina) obtained from the Baltic Sea. The bacterium is a mesophilic, typical marine bacterium. It is a chemoheterotrophic aerobic bacterium with the potential of denitrification. Growth optima are at 25 °C, pH 5.5, and 3 % NaCl. The distinguished phylogenetic position separates Kiloniella from other alphaproteobacterial orders. The 16S rRNA gene sequence revealed a distant relationship to species of several orders of the Alphaproteobacteria with less than 91 % sequence similarity. This gives rise to the recognition of Kiloniella as a representative of a new order of the Alphaproteobacteria, the Kiloniellales. Phylogenetic analyses revealed a distinct cluster of Kiloniella with an uncharacterized bacterium (isolate KOPRI 13522) from hydrothermal plumes. This cluster forms a larger group together with the distantly related Terasakiella pusilla (88.4 % sequence similarity of the 16S rRNA gene) and the Thalassospira species (88.9–90.2 % sequence similarity). These genera are supposed to form separate families within the Kiloniellales.

Description: A multi-model analysis of Atlantic multidecadal variability is performed with the following aims: to investigate the similarities to observations; to assess the strength and relative importance of the different elements of the mechanism proposed by Delworth et al. (J Clim 6:1993–2011, 1993) (hereafter D93) among coupled general circulation models (CGCMs); and to relate model differences to mean systematic error. The analysis is performed with long control simulations from ten CGCMs, with lengths ranging between 500 and 3600 years. In most models the variations of sea surface temperature (SST) averaged over North Atlantic show considerable power on multidecadal time scales, but with different periodicity. The SST variations are largest in the mid-latitude region, consistent with the short instrumental record. Despite large differences in model configurations, we find quite some consistency among the models in terms of processes. In eight of the ten models the mid-latitude SST variations are significantly correlated with fluctuations in the Atlantic meridional overturning circulation (AMOC), suggesting a link to northward heat transport changes. Consistent with this link, the three models with the weakest AMOC have the largest cold SST bias in the North Atlantic. There is no linear relationship on decadal timescales between AMOC and North Atlantic Oscillation in the models. Analysis of the key elements of the D93 mechanisms revealed the following: Most models present strong evidence that high-latitude winter mixing precede AMOC changes. However, the regions of wintertime convection differ among models. In most models salinity-induced density anomalies in the convective region tend to lead AMOC, while temperature-induced density anomalies lead AMOC only in one model. However, analysis shows that salinity may play an overly important role in most models, because of cold temperature biases in their relevant convective regions. In most models subpolar gyre variations tend to lead AMOC changes, and this relation is strong in more than half of the models.

Description: Cold seeps on the Hikurangi Margin off New Zealand exhibit various seabed morphologies producing different intensity patterns in backscatter images. Acoustic backscatter characteristics of 25 investigated seep sites do not show a continuous range of patterns between two end members, but fall into four distinct types characterised by variations in backscatter intensity, distribution and inferred structural heights. The types reflect different carbonate morphologies including up to 20 m high structures (type 1), low-relief crusts (type 2), scattered blocks (type 3) and carbonate free sites (type 4). Each seep corresponds to a single type; ntermediates were not observed. Although the observed morphologies and backscatter patterns may have been caused by variations in sediment burial of seep carbonates or differential exhumation by erosion, they probably epresent varying onsets of authigenic carbonate precipitation. Precipitation of carbonate is episodic, which is likely the result of internal forcing. Blocking and subsequent reorganisation of the seep plumbing system lead to abandonment of old seeps and formation of new sites.

Description: Why a chapter on Perspectives and Integration in SOLAS Science in this book? SOLAS science by its nature deals with interactions that occur: across a wide spectrum of time and space scales, involve gases and particles, between the ocean and the atmosphere, across many disciplines including chemistry, biology, optics, physics, mathematics, computing, socio-economics and consequently interactions between many different scientists and across scientific generations. This chapter provides a guide through the remarkable diversity of cross-cutting approaches and tools in the gigantic puzzle of the SOLAS realm. Here we overview the existing prime components of atmospheric and oceanic observing systems, with the acquisition of ocean–atmosphere observables either from in situ or from satellites, the rich hierarchy of models to test our knowledge of Earth System functioning, and the tremendous efforts accomplished over the last decade within the COST Action 735 and SOLAS Integration project frameworks to understand, as best we can, the current physical and biogeochemical state of the atmosphere and ocean commons. A few SOLAS integrative studies illustrate the full meaning of interactions, paving the way for even tighter connections between thematic fields. Ultimately, SOLAS research will also develop with an enhanced consideration of societal demand while preserving fundamental research coherency. The exchange of energy, gases and particles across the air-sea interface is controlled by a variety of biological, chemical and physical processes that operate across broad spatial and temporal scales. These processes influence the composition, biogeochemical and chemical properties of both the oceanic and atmospheric boundary layers and ultimately shape the Earth system response to climate and environmental change, as detailed in the previous four chapters. In this cross-cutting chapter we present some of the SOLAS achievements over the last decade in terms of integration, upscaling observational information from process-oriented studies and expeditionary research with key tools such as remote sensing and modelling. Here we do not pretend to encompass the entire legacy of SOLAS efforts but rather offer a selective view of some of the major integrative SOLAS studies that combined available pieces of the immense jigsaw puzzle. These include, for instance, COST efforts to build up global climatologies of SOLAS relevant parameters such as dimethyl sulphide, interconnection between volcanic ash and ecosystem response in the eastern subarctic North Pacific, optimal strategy to derive basin-scale CO2 uptake with good precision, or significant reduction of the uncertainties in sea-salt aerosol source functions. Predicting the future trajectory of Earth’s climate and habitability is the main task ahead. Some possible routes for the SOLAS scientific community to reach this overarching goal conclude the chapter.

Description: The features of 30-60-day convection oscillations over the subtropical western North Pacific (WNP) were investigated, along with the degree of tropical-subtropical linkage between the oscillations over the WNP during summer 1998. It was found that 30-60-day oscillations were extremely strong in that summer over both the subtropical and tropical WNP, providing a unique opportunity to study the behavior of subtropical oscillations and their relationship to tropical oscillations. Further analyses indicated that 30-60-day oscillations propagate westwards over the subtropical WNP and reach eastern China. In addition, 30-60-day oscillations in the subtropics are affected by those over the South China Sea (SCS) and tropical WNP through two mechanisms: (1) direct propagation from the tropics into the subtropics; and (2) a seesaw pattern between the tropics and subtropics, with the latter being predominant

Description: We report fossil coral records from the Seychelles comprising individual time slices of 14–20 sclerochronological years between 2 and 6.2 kyr BP to reconstruct changes in the seasonal cycle of western Indian Ocean sea surface temperature (SST) compared to the present (1990–2003). These reconstructions allowed us to link changes in the SST bimodality to orbital changes, which were causing a reorganization of the seasonal insolation pattern. Our results reveal the lowest seasonal SST range in the Mid-Holocene (6.2–5.2 kyr BP) and around 2 kyr BP, while the highest range is observed around 4.6 kyr BP and between 1990 and 2003. The season of maximum temperature shifts from austral spring (September to November) to austral autumn (March to May), following changes in seasonal insolation over the past 6 kyr. However, the changes in SST bimodality do not linearly follow the insolation seasonality. For example, the 5.2 and 6.2 kyr BP corals show only subtle SST differences in austral spring and autumn. We use paleoclimate simulations of a fully coupled atmosphere–ocean general circulation model to compare with proxy data for the Mid-Holocene around 6 kyr BP. The model results show that in the Mid-Holocene the austral winter and spring seasons in the western Indian Ocean were warmer while austral summer was cooler. This is qualitatively consistent with the coral data from 6.2 to 5.2 kyr BP, which shows a similar reduction in the seasonal amplitude compared to the present day. However, the pattern of the seasonal SST cycle in the model appears to follow the changes in insolation more directly than indicated by the corals. Our results highlight the importance of ocean–atmosphere interactions for Indian Ocean SST seasonality throughout the Holocene. In order to understand Holocene climate variability in the countries surrounding the Indian Ocean, we need a much more comprehensive analysis of seasonally resolved archives from the tropical Indian Ocean. Insolation data alone only provides an incomplete picture.

Description: Seasonal to interannual variations of the Equatorial Undercurrent (EUC) in the central Atlantic at 23°W are studied using shipboard observation taken during the period 1999-2011 as well as moored velocity time series covering the period May 2005-June 2011. The seasonal variations are dominated by an annual harmonic of the EUC transport and the EUC core depth (both at maximum during September), and a semiannual harmonic of the EUC core velocity (maximum during April and September). Substantial interannual variability during the period of moored observation included anomalous cold/warm equatorial Atlantic cold tongue events during 2005/2008. The easterly winds in the western equatorial Atlantic during boreal spring that represent the preconditioning of cold/warm events were strong/weak during 2005/2008 and associated with strong/weak boreal summer EUC transport. The anomalous year 2009 was instead associated with weak preconditioning and smallest EUC transport on record from January to July, but during August coldest SST anomalies in the eastern equatorial Atlantic were observed. The interannual variations of the EUC are discussed with respect to recently described variability of the tropical Atlantic Ocean.

Description: The volcano Cotopaxi in South America is 5,897 m high and is one of the highest active volcanoes of the world and the second highest volcano in the Andes after the Chimborazo (6,310 m). In Ecuador, there are more than 20 volcanoes contributing to the spectacular mountain range diving this country between the western and eastern lowlands. There have been more than 50 reports of volcanic activity at Cotopaxi since 1738, among which those from the years 1744, 1768, and 1877 are the largest. During the 1877 eruption, the whole summit glacier collapsed and a huge mudflow spread out for more than 100 km and flooded the city of Latacunga. Five years prior to this catastrophic event, the German geologist Wilhelm Reiss from the University of Heidelberg ascended Cotopaxi for the first time together with his supporter Angel M. Escobar from Columbia.

Description: The neighbouring volcanoes Villarrica and Llaima are two of the most active volcanoes in Chile and both currently degas continuously. We present a semi-continuous time series of SO2 fluxes for Villarrica and Llaima volcanoes. The time series was obtained using five scanning Mini-Differential Optical Absorption Spectrometers (Mini-DOAS, UV spectrometers) over 6 months (13 February to 31 July 2010) and is based on 6,829 scans for Villarrica and 7,165 scans for Llaima. Statistical analyses of the SO2 flux time series reveal a periodicity of degassing maxima about every 7 days, and further a conspicuous synchronicity of the degassing maxima and minima between the two volcanoes. Intra-day variations in SO2 fluxes also show a striking correlation between Villarrica and Llaima. All these patterns correlate well with the trend of the modelled solid Earth tide curves, where the 7-day degassing maxima correspond with both the fortnightly tidal maxima and minima. The intra-day degassing peaks mostly correlate well with the periods of maximum deformation rates during the diurnal tidal cycle, and further with semidiurnal minima in atmospheric pressure, a phenomenon we refer to as “the tidal pump”. As there is little time lag between the tidal action and the changes in degassing rates, we infer that degassing at both volcanoes is controlled by conduit convection, involving physical separation between gas and magma at comparatively shallow levels. Variations in daily degassing rates were up to a factor of ca. 12 and 10 for Villarrica and Llaima, respectively, without any noticeable changes in the periodicity. We thus suggest that the described cyclic variations must be taken into account for all comparable volcanoes when using gas monitoring as a tool for volcanic hazard mitigation.

Description: This study investigates the global warming response of the Walker Circulation and the other zonal circulation cells (represented by the zonal stream function), in CMIP3 and CMIP5 climate models. The changes in the mean state are presented as well as the changes in the modes of variability. The mean zonal circulation weakens in the multi model ensembles nearly everywhere along the equator under both the RCP4.5 and SRES A1B scenarios. Over the Pacific the Walker Circulation also shows a significant eastward shift. These changes in the mean circulation are very similar to the leading mode of interannual variability in the tropical zonal circulation cells, which is dominated by El Niño Southern Oscillation variability. During an El Niño event the circulation weakens and the rising branch over the Maritime Continent shifts to the east in comparison to neutral conditions (vice versa for a La Niña event). Two-thirds of the global warming forced trend of the Walker Circulation can be explained by a long-term trend in this interannual variability pattern, i.e. a shift towards more El Niño-like conditions in the multi-model mean under global warming. Further, interannual variability in the zonal circulation exhibits an asymmetry between El Niño and La Niña events. El Niño anomalies are located more to the east compared with La Niña anomalies. Consistent with this asymmetry we find a shift to the east of the dominant mode of variability of zonal stream function under global warming. All these results vary among the individual models, but the multi model ensembles of CMIP3 and CMIP5 show in nearly all aspects very similar results, which underline the robustness of these results. The observed data (ERA Interim reanalysis) from 1979 to 2012 shows a westward shift and strengthening of the Walker Circulation. This is opposite to what the results in the CMIP models reveal. However, 75 % of the trend of the Walker Circulation can again be explained by a shift of the dominant mode of variability, but here towards more La Niña-like conditions. Thus in both climate change projections and observations the long-term trends of the Walker Circulation seem to follow to a large part the pre-existing dominant mode of internal variability.

Description: Lycoteuthis lorigera is among the most abundant mesopelagic squid on the continental slope of the south Atlantic. It is the dominant prey in some commercially harvested groundfish. Despite its abundance and importance in the mesopelagic foodweb, its general biology is poorly known. In this study, the spawning pattern and fecundity of L. lorigera from southern African waters were investigated. Both histological examination and length frequency analysis of ovaries in various stages of development revealed that the ovulation pattern of L. lorigera is asynchronous, which indicates a spawning strategy where batches of eggs are spawned repeatedly over time. More specifically, ovulation is group synchronous, where distinct batches of 1,200–2,400 eggs ripen in the ovary and accumulate in the oviducts. The potential fecundity was estimated to be 20,000–50,000 in immature females (n = 6) and 8,000–25,000 in mature females (n = 21). The number of ripe eggs in the oviducts suggests that batches of spawned egg masses contain between 1,000 and 4,000 eggs. The reproductive strategy of L. lorigera is discussed and compared to the reproductive strategies of oceanic squid inhabiting the continental slope of southern Africa.

Description: Mt. Etna is the largest and one of the best-studied volcanoes in Europe. It represents a highly active basaltic volcano on top of the active Apennine thrust belt. The instability of its eastern flank has been described as an important preconditioning factor for the occurrence of submarine mass wasting events. In order to better understand the processes that may cause submarine slope failures, a new dataset including seismic, hydroacoustic and core data was collected during RV Meteor cruise M86/2 from December 2011 to January 2012. Seismic profiles and sediment cores reveal repeated mass transport deposits (MTD), indicating a long history of landslides in the working area. Some of the sampled MTDs and their surrounding strata contain volcaniclastic debris, indicating that slope failures may be controlled by volcanic and non-volcanic processes. Several tephra layers directly cover MTDs, which is regarded as an indicator for the possibility that several flank failures occur immediately before or very early during an eruption.

Description: In 1996, after 150 years of relative calm, Turrialba Volcano was reawakening. A visible plume and serious damage to surrounding vegetation due to acid rain are the most obvious signals. As part of the Network for Observation of Volcanic and Atmospheric Change project, four gas-monitoring stations were initially installed on the west flank of the volcano with the purpose of measuring sulphur dioxide emissions during this period of increased activity using the scanning-differential optical absorption spectroscopy technique. We present here the results of semicontinuous gas flux measurements over a period of 5 years (from 2008 to 2012), providing a novel data set that documents a relatively rapid increase in SO2 fluxes from around 350 t day−1 to around 4,000 t day−1 leading up to an eruptive period, followed by a gradual return to the former baseline values. Gas flux data were also compared with seismic data for selected periods of interest, providing insights into the link between degassing and seismicity. The most important result from this comparison is the identification of an inflexion point in the gas emissions followed by a clearly increasing trend in seismic activity, distinguishable 6 months prior to a phreatic eruptive event that occurred on 5 January 2010. This signal can be interpreted as a possible indicator of future eruptive events. Monitoring of SO2 thus complements seismic monitoring as a forecasting tool for eruptive events. Such monitoring is critical considering the proximity of Turrialba to the Central Valley, an area inhabited by more than 50 % of Costa Rica’s population.

Description: In many marine biogeographic realms, bioeroding sponges dominate the internal bioerosion of calcareous substrates such as mollusc beds and coral reef framework. They biochemically dissolve part of the carbonate and liberate so-called sponge chips, a process that is expected to be facilitated and accelerated in a more acidic environment inherent to the present global change. The bioerosion capacity of the demosponge Cliona celata Grant, 1826 in subfossil oyster shells was assessed via alkalinity anomaly technique based on 4 days of experimental exposure to three different levels of carbon dioxide partial pressure (pCO(2)) at ambient temperature in the cold-temperate waters of Helgoland Island, North Sea. The rate of chemical bioerosion at present-day pCO(2) was quantified with 0.08-0.1 kg m(-2) year(-1). Chemical bioerosion was positively correlated with increasing pCO(2), with rates more than doubling at carbon dioxide levels predicted for the end of the twenty-first century, clearly confirming that C. celata bioerosion can be expected to be enhanced with progressing ocean acidification (OA). Together with previously published experimental evidence, the present results suggest that OA accelerates sponge bioerosion (1) across latitudes and biogeographic areas, (2) independent of sponge growth form, and (3) for species with or without photosymbionts alike. A general increase in sponge bioerosion with advancing OA can be expected to have a significant impact on global carbonate (re)cycling and may result in widespread negative effects, e.g. on the stability of wild and farmed shellfish populations, as well as calcareous framework builders in tropical and cold-water coral reef ecosystems.

Description: Simultaneous mooring arrays were maintained along the path of the Equatorial Undercurrent (EUC) at three longitudes (23°W, 10°W, and 0°E), from October 2007 to June 2011, as part of the CLIVAR Tropical Atlantic Climate Experiment. The measurements allow for the first time a description of the seasonal cycle and interannual variability of the EUC across the Atlantic basin. The mean transport of the EUC at 23°W is 14.3 ± 0.6 Sv, decreasing to 12.1 ± 0.9 and 9.4 ± 0.6 Sv at 10°W and 0°E, respectively. The EUC shows a changing seasonal cycle across the basin: at 23°W, the strongest EUC transport occurs in boreal fall in association with maximum easterly wind stress, at 10°W the EUC transport shows a semiannual cycle with a maximum in boreal spring and fall, while at 0°E the EUC has a single spring maximum. At all locations the EUC core exhibits a similar seasonal vertical migration, with shallowest core depths occurring in boreal spring and deepest core depths in boreal fall. The maximum core intensity occurs in boreal spring all across the basin, when the EUC is shallow, during the annual wind relaxation. The weakest EUC core intensity occurs during the boreal summer cold tongue phase, especially in the eastern part of the basin. At both 23°W and 10°W, a deep extension of the EUC occurs in boreal summer, which increases the transport in the lower thermocline and partially offsets the weaker upper EUC transport during boreal summer. No clear linkage could be established between the interannual variability of the EUC in the eastern part of the basin and the intensity of the summer cold tongue, despite evidence for such a linkage in the western part of the basin.

Description: Some studies have demonstrated that elevated CO2 concentrations in ocean waters negatively impact metabolism and development of marine fish. Particularly, early developmental stages are probably more susceptible to ocean acidification due to insufficient regulations of their acid-base balance. Transgenerational acclimation can be an important mechanism to mediate impacts of increased CO2 on marine species, yet very little is known about the potential of parental effects in teleosts. Therefore, transgenerational effects were investigated on life history in juvenile three-spined sticklebacks Gasterosteus aculeatus by acclimating parents (collected in April 2012, 55A degrees 03'N, 8A degrees 44'E) and offspring to ambient (similar to 400 A mu atm) and elevated (similar to 1,000 A mu atm) CO2 levels and measured parental fecundity as well as offspring survival, growth and otolith characteristics. Exposure to elevated CO2 concentrations led to an increase in clutch size in adults as well as increased juvenile survival and growth rates between 60 and 90 days post-hatch and enlarged otolith areas compared with fish from ambient CO2 concentrations. Moreover, transgenerational effects were observed in reduced survival and body size 30 days post-hatch as well as in enlarged otoliths at the end of the experiment, when fathers or both parents were acclimated to the high-CO2 environment. These results may suggest that elevated CO2 concentrations had rather positive effects on life-history traits of three-spined sticklebacks, but that parental acclimation can modify these effects without improving offspring fitness. Although the mechanistic basis of such transgenerational acclimation remains unclear, selective gradients within generations seem to determine the direction of transgenerational effects.

Description: This study presents laser step-heating 40Ar/39Ar age determinations of basaltic lava samples from Tamu Massif, the oldest and largest edifice of the submarine Shatsky Rise in the northwest Pacific and Earth’s proposed largest volcano. The rocks were recovered during Integrated Ocean Drilling Program Expedition 324, which cored 160 m into the igneous basement near the summit of Tamu Massif. The analyzed lavas cover all three major stratigraphic groups penetrated at this site and confirm a Late Jurassic/Early Cretaceous age for the onset of Shatsky Rise volcanism. Lavas analyzed from the lower and middle section of the hole yield plateau ages between 144.4 ± 1.0 and 143.1 ± 3.3 Ma with overlapping analytical errors (2σ), whereas a sample from the uppermost lava group produced a significantly younger age of 133.9 ± 2.3 Ma suggesting a late or rejuvenated phase of volcanism. The new geochronological data infer minimum (average) melt production rates of 0.63–0.84 km3/a over a time interval of 3–4 million years consistent with the presence of a mantle plume.

Description: Sea surface temperatures (SSTs) in the eastern tropical Atlantic are crucial for climate variability within the tropical belt. Despite this importance, state-of-the-art climate models show a large SST warm bias in this region. Knowledge about the seasonal mixed layer (ML) heat budget is a prerequisite for understanding SST mean state and its variability. Within this study all contributions to the seasonal ML heat budget are estimated at four locations within the Atlantic cold tongue (ACT) that are representative for the western (0°N, 23°W), central (0°N, 10°W) and eastern (0°N, 0°E) equatorial as well as the southern (10°S, 10°W) ACT. To estimate the contribution of the diapycnal heat flux due to turbulence an extensive data set of microstructure observations collected during ten research cruises between 2005 and 2012 is analyzed. The results for the equatorial ACT indicate that with the inclusion of the diapycnal heat flux the seasonal ML heat budget is balanced. Within the equatorial region, the diapycnal heat flux is essential for the development of the ACT. It dominates over all other cooling terms in the central and eastern equatorial ACT, while it is of similar size as the zonal advection in the western equatorial ACT. In contrast, the SST evolution in the southern ACT region can be explained entirely by air-sea heat fluxes.

Description: Observations show a multidecadal signal in the North Atlantic ocean, but the underlying mechanism and cause of its timescale remain unknown. Previous studies have suggested that it may be driven by the North Atlantic Oscillation (NAO), which is the dominant pattern of winter atmospheric variability. To further address this issue, the global ocean general circulation model, Nucleus for European Modelling of the Ocean (NEMO), is driven using a 2,000 years long white noise forcing associated with the NAO. Focusing on key ocean circulation patterns, we show that the Atlantic Meridional Overturning Circulation (AMOC) and Sub-polar gyre (SPG) strength both have enhanced power at low frequencies but no dominant timescale, and thus provide no evidence for a oscillatory ocean-only mode of variability. Instead, both indices respond linearly to the NAO forcing, but with different response times. The variability of the AMOC at 30°N is strongly enhanced on timescales longer than 90 years, while that of the SPG strength starts increasing at 15 years. The different response characteristics are confirmed by constructing simple statistical models that show AMOC and SPG variability can be related to the NAO variability of the previous 53 and 10 winters, respectively. Alternatively, the AMOC and the SPG strength can be reconstructed with Auto-regressive (AR) models of order seven and five, respectively. Both statistical models reconstruct interannual and multidecadal AMOC variability well, while on the other hand, the AR(5) reconstruction of the SPG strength only captures multidecadal variability. Using these methods to reconstruct ocean variables can be useful for prediction and model intercomparision.

Description: Atmospheric carbon dioxide emissions cause a decrease in the pH and aragonite saturation state of surface ocean water. As a result, calcifying organisms are expected to suffer under future ocean conditions, but their physiological responses may depend on their nutrient status. Because many coral reefs experience high inorganic nutrient loads or seasonal changes in nutrient availability, reef organisms in localized areas will have to cope with elevated carbon dioxide and changes in inorganic nutrients. Halimeda opuntia is a dominant calcifying primary producer on coral reefs that contributes to coral reef accretion. Therefore, we investigated the carbon and nutrient balance of H. opuntia exposed to elevated carbon dioxide and inorganic nutrients. We measured tissue nitrogen, phosphorus and carbon content as well as the activity of enzymes involved in inorganic carbon uptake and nitrogen assimilation (external carbonic anhydrase and nitrate reductase, respectively). Inorganic carbon content was lower in algae exposed to high CO2, but calcification rates were not significantly affected by CO2 or inorganic nutrients. Organic carbon was positively correlated to external carbonic anhydrase activity, while inorganic carbon showed the opposite correlation. Carbon dioxide had a significant effect on tissue nitrogen and organic carbon content, while inorganic nutrients affected tissue phosphorus and N:P ratios. Nitrate reductase activity was highest in algae grown under elevated CO2 and inorganic nutrient conditions and lowest when phosphate was limiting. In general, we found that enzymatic responses were strongly influenced by nutrient availability, indicating its important role in dictating the local responses of the calcifying primary producer H. opuntia to ocean acidification.

Description: Coralline algae (Corallinales, Rhodophyta) that form rhodoliths are important ecosystem engineers and carbonate producers in many polar coastal habitats. This study deals with rhodolith communities from Floskjeret (78°18′N), Krossfjorden (79°08′N), and Mosselbukta (79°53′N), off Spitsbergen Island, Svalbard Archipelago, Norway. Strong seasonal variations in temperature, salinity, light regime, sea-ice coverage, and turbidity characterize these localities. The coralline algal flora consists of Lithothamnion glaciale and Phymatolithon tenue. Well-developed rhodoliths were recorded between 27 and 47 m water depth, while coralline algal encrustations on lithoclastic cobbles were detected down to 77 m water depth. At all sites, ambient waters were saturated with respect to both aragonite and calcite, and the rhodolith beds were located predominately at dysphotic water depths. The rhodolith-associated macrobenthic fauna included grazing organisms such as chitons and echinoids. With decreasing water depth, the rhodolith pavements were regularly overgrown by non-calcareous Polysiphonia-like red algae. The corallines are thriving and are highly specialized in their adaptations to the physical environment as well as in their interaction with the associated benthic fauna, which is similar to other polar rhodolith communities. The marine environment of Spitsbergen is already affected by a climate-driven ecological regime shift and will lead to an increased borealization in the near future, with presently unpredictable consequences for coralline red algal communities.

Description: The paper presents data on the petrology and geochemistry of plutonic rocks dredged from the Stalemate Fracture Zone, Northwest Pacific Ocean, during Cruise SO201-1 of the R/V “Sonne”. We proposed also the reconstruction of their formation conditions and interpretation of their tectonic evolution. The genesis of gabbroids found among plutonic rocks composing the Cretaceous–Paleogene basement of the northwestern part of the Pacific Ocean was related to magmatism at the ancient spreading center and provides record of the evolution of the parental magmatic melts of N-MORB. Along with related peridotites, basalts, and dolerites, these rocks can be attributed to the disintegrated the Cretaceous–Paleogene oceanic lithosphere of the Pacific Ocean. The shallow mantle beneath the ancient oceanic crust of this area is made up of depleted magmatic spinel lherzolite, harzburgite, and dunite. The fact that gabbro-diorite and diorite that are not genetically related to the rocks of the Cretaceous–Paleogene basement of the Northwest Pacific occur at the eastern termination of the Stalemate Fracture Zone possibly reflects the complicated structure of the tectonic collage of rocks of different age that were produced in different geodynamic environments and were later tectonically brought together near the frontal portion of the Aleutian island arc. Judging by the isotopic–geochemical characteristics of these rocks, they cannot be classed with the family of oceanic plagiogranites. Deformations of the oceanic basement can be discerned throughout the whole Stalemate Fracture Zone as brecciation and large-amplitude vertical displacements within the oceanic lithosphere.

Description: Ship-based acoustic Doppler current profiler (ADCP) velocity measurements collected by several major field programs in the tropical Atlantic are averaged and combined with estimates of the mean near-surface velocity derived from drifters and Argo float surface drifts (ADCP+D) to describe the mean cross-equatorial and vertical structure of the meridional currents along 23°W and 10°W. Data from moored ADCPs and fixed-depth current meters, a satellite-derived velocity product, and a global ocean reanalysis were additionally used to evaluate the mean ADCP+D meridional velocity. The dominant circulation features in the long-term mean ADCP+D meridional velocity in the upper 100 m are the tropical cells (TCs) located approximately between 5°S and 5°N, with near-surface poleward flow and subsurface equatorward flow that is stronger and shallower in the northern cell compared to the southern cell. The thickness of the surface limb of the TCs decreases and the northern cell is found to shift further south of the equator from the central to eastern tropical Atlantic. Analysis of two-season means estimated from the ship-based ADCP, near-surface drift, and moored velocity data, as well as the simulated fields, indicates that the maximum poleward velocity in the surface limb of the TCs intensifies during December–May along 23°W largely due to seasonal compensation between the geostrophic and ageostrophic (or wind-driven) components of the meridional velocity, whereas the maximum equatorward flow in the subsurface limb of the northern cell intensifies during June–November along both 23°W and 10°W due to the seasonality of the geostrophic meridional velocity.

Description: Llaima is one of the most active volcanoes of the Chilean volcanic front with recent explosive eruptions in 2008 and 2009. Understanding how the volcano evolved to its present state is essential for predictions of its future behavior. The post-glacial succession of explosive volcanic eruptions of Llaima stratovolcano started with two caldera-forming eruptions at ∼16 and ∼15 ka, that emplaced two large-volume basaltic-andesitic ignimbrites (unit I). These are overlain by a series of fall deposits (unit II) changing from basaltic-andesitic to dacitic compositions with time. The prominent compositionally zoned, dacitic to andesitic Llaima pumice (unit III) was formed by a large Plinian eruption at ∼10 ka that produced andesitic surge deposits (unit IV) in its terminal phase. The following unit V represents a time interval of ∼8,000 years during which at least 30 basaltic to andesitic ash and lapilli fall deposits with intercalated volcaniclastic sediments and paleosols were emplaced. Bulk rock, mineral, and glass chemical data constrain stratigraphic changes in magma compositions and pre-eruptive conditions that we interpret in terms of four distinct evolutionary phases. Phase 1 (=unit I) magmas have lower large ion lithophile (LIL)/high field strength (HFS) element ratios compared to younger magmas and thus originated from a mantle source less affected by slab-derived fluids. They differentiated in a reservoir at mid-crustal level. During the post-caldera phase 2 (=units II–IV), relatively long residence times between eruptions allowed for increasingly differentiated magmas to form in a reservoir in the middle crust. Fractional crystallization led to volatile enrichment and oversaturation and is the driving force for the large Plinian eruption of the most evolved (unit III) dacite at Llaima, although replenishment by hot andesite probably triggered the eruption. During the subsequent phase 3 (=unit V 〉3 ka), frequent mafic replenishments at mid-crustal storage levels favored shorter residence times limiting erupted magma compositions to water-undersaturated basaltic andesites and andesites. At around 3 ka, the magma storage level for phase 4 (=unit V 〈3 ka to present) shifted to the uppermost crust where the hot magmas partly assimilated the granitic country rock. Although water contents of these basaltic andesites were low, the low-pressure storage facilitated water saturation before eruption. The change in magma storage level at 3 ka was responsible for the dramatic increase in eruption frequency compared to the older Llaima history. We suggest that the change from middle to upper crust magma storage is caused by a change in the stress regime below Llaima from transpression to tension.

Description: Mafic basaltic-andesitic volcanic rocks from the Andean Southern Volcanic Zone (SVZ) exhibit a northward increase in crustal components in primitive arc magmas from the Central through the Transitional and Northern SVZ segments. New elemental and Sr-Nd-high-precision Pb isotope data from the Quaternary arc volcanic centres of Maipo (NSVZ) and Infernillo and Laguna del Maule (TSVZ) are argued to reflect mainly their mantle source and its melting. For the C-T-NSVZ, we identify two types of source enrichment: one, represented by Antuco in CSVZ, but also present northward along the arc, was dominated by fluids which enriched a pre-metasomatic South Atlantic depleted MORB mantle type asthenosphere. The second enrichment was by melts having the characteristics of upper continental crust (UCC), distinctly different from Chile trench sediments. We suggest that granitic rocks entered the source mantle by means of subduction erosion in response to the northward increasingly strong coupling of the converging plates. Both types of enrichment had the same Pb isotope composition in the TSVZ with no significant component derived from the subducting oceanic crust. Pb-Sr-Nd isotopes indicate a major crustal compositional change at the southern end of the NSVZ. Modelling suggests addition of around 2 % UCC for Infernillo and 5 % for Maipo

Description: Between 33A degrees S and 47A degrees S, the southern Chile forearc is affected by the subduction of the aseismic Juan Fernandez Ridge, several major oceanic fracture zones on the subducting Nazca Plate, the active Chile Ridge spreading centre, and the underthrusting Antarctic Plate. The heat flow through the forearc was estimated using the depth of the bottom simulating reflector obtained from a comprehensive database of reflection seismic profiles. On the upper and middle continental slope along the whole forearc, heat flow is about 30-60 mW m(-2), a range of values common for the continental basement and overlying slope sediments. The actively deforming accretionary wedge on the lower slope, however, in places shows heat flow reaching about 90 mW m(-2). This indicates that advecting pore fluids from deeper in the subduction zone may transport a substantial part of the heat there. The large size of the anomalies suggests that fluid advection and outflow at the seafloor is overall diffuse, rather than being restricted to individual fault structures or mud volcanoes and mud mounds. One large area with very high heat flow is associated with a major tectonic feature. Thus, above the subducting Chile Ridge at 46A degrees S, values of up to 280 mW m(-2) indicate that the overriding South American Plate is effectively heated by subjacent zero-age oceanic plate material.

Description: Continuous surface cores of cold-seep carbonates were recovered offshore Pacific Nicaragua and Costa Rica from 800 to 1,500-m water depths (Meteor 66/3) in order to decipher their evolution and methane enriched fluid emanation in contrasting geological settings. Cores from the mounds Iguana, Perezoso, Baula V and from the Jaco Scarp escarpment were used for a multi-method approach. For both settings aragonite was revealed as dominant authigenic carbonate phase in vein fillings and matrix cementation, followed by Mg-calcite as second most abundant. This common precipitation process of CaCO3 polymorphs could be ascribed as indirectly driven by chemical changes of the advecting pore water due to anaerobic oxidation of methane. A more direct influence of seep-related microbial activity on the authigenic mineral assemblage in both settings is probably reflected by the observed minor amounts of dolomite and a dolomite-like CaMg carbonate (MgCO3 ~ 42 %). δ13C data of Jaco Scarp samples are significantly lower (−43 to −56 ‰ PDB) than for mound samples (−22 to −36 ‰ PDB), indicating differences in fluid composition and origin. Noteworthy, δ18O values of Scarp samples correlate most closely with the ocean signature at their time of formation. Documenting the archive potential, a high resolution case study of a mound core implies at least 40 changes in fluid supply within a time interval of approximately 14 ky. As most striking difference, the age data indicate a late-stage downward-progressing cementation front for all three mound cap structures (approx. 2–5 cm/ky), but a significantly faster upward carbonate buildup in the bulging sediments on top of the scarp environment (approx. 120 cm/ky). The latter data set leads to the hypothesis of chemoherm carbonate emplacement in accord with reported sedimentation rates until decompression of the advective fluid system, probably caused by the Jaco Scarp landslide and dating this to approximately 13,000 years ago.