ALBERT

Description: Wochenbericht vom 14.07.-20.07.2014 (Port Louis/Mauritius)

Description: Knowledge of the parameter K (turbulent diffusivity/"mixing intensity") is a key to understand transport processes of matter and energy in the ocean. Especially the almost vertical component of K across the ocean stratification (diapycnal diffusivity) is vital for research on biogeochemical cycles or greenhouse gas budgets. Recent boost in precision of water velocity data that can be obtained from vessel-mounted acoustic instruments (vmADCP) allows identifying ocean regions of elevated diapycnal diffusivity during research cruises - in high horizontal resolution and without extra ship time needed. This contribution relates acoustic data from two cruises in the Tropical North East Atlantic Oxygen Minimum Zone to simultaneous field observations of diapycnal diffusivity: pointwise measurements by a microstructure profiler as well as one integrative value from a large scale Tracer Release Experiment.

Description: In this study, the stratospheric winter circulation in the coupled middle atmosphere ocean model MAECHAM5/MPI-OM, is analysed. Due to the dynamical and thermodynamical interaction with the ocean, the simulated atmospheric circulation is affected by the internal variability of the ocean. Differences of the stratospheric winter circulation between MAECHAM5/MPI-OM and former MAECHAM5 simulations may be attributed to the interactive ocean. This work is divided into three parts: first the climatology of the model is examined, then major Sudden Stratospheric Warmings (SSWs), and at last the relationship between these warmings and tropospheric blockings. To examine how the model reproduces the stratospheric winter circulation, the climatology of the zonal mean zonal wind and of planetary waves of zonal wavenumber 1 to 3, are carefully analysed and compared with those obtained from ERA-40 observations. While the zonal mean zonal wind is in good agreement with observations, amplitudes and phases of zonal wavenumber 2 are not well represented. Major SSWs are analysed because of the strong impact that such phenomena can have throughout the atmosphere, influencing the weather at the surface for several weeks after the onset of the warming. To identify major SSWs, a new algorithm based on the 10 hPa zonal mean zonal wind at 60°N, is developed. This is done because a comparison between a recent study by Charlton and Polvani (2007) and the Freie Universität Berlin climatology of mid-winter major SSWs, reveals a significant disagreement. The new algorithm is applied to two databases: one obtained from the model simulation and one from the ERA-40 assimilation. ERA-40 data are used for validation of MAECHAM5/MPI-OM. Comparison of the obtained frequencies of major SSWs shows that in the model a slightly higher number of events occurs. While in ERA-40 the average frequency is of 0.60 events per year, in the model it is of 0.70 events per year. The seasonal distributions show also that the highest number of major SSWs occurs in January and in February respectively for ERA-40 and model data, which is improved for MAECHAM5/MPI-OM compared to former MAECHAM5 simulations. In this work, unlike previous model studies, the state of the polar vortex is also examined during the pre-warming phase of major SSWs, by analysing the planetary wave activity, to determine the behaviour of waves with different zonal wavenumbers. Only planetary waves of zonal wavenumber 1 and 2 appear to have a key role in the development of major SSWs, with wavenumber-1 events being more frequent than wavenumber-2 events and a ratio of 57:13 similar as observed. Because of the influence of tropospheric blockings on major SSWs via alteration of planetary waves, a correlation analysis is performed to determine if the model represents this relationship well. It appears that Pacific blockings are correlated with wavenumber-2 major SSWs although a larger number of wavenumber-2 events would be necessary to make such assertion. No significant correlation is instead obtained for wavenumber-1 major warmings.

Description: This diploma thesis investigates variations in mixing ratios of very short lived substances (VSLS) during the DRIVE (Diurnal and Regional Variability of halogen Emissions) campaign in the tropical East Atlantic conducted during P399 2/3 from May to June 2010. The main focus lies on the diurnal and regional variability of three halocarbons influenced by meteorological factors at six 24 h stations. For this reason, regular ship measurements of temperature, wind, air pressure and humidity were complemented by radiosonde launches and air samples for the trace gas investigation. According to the radiosonde measurements a changeover between tropical and extra tropical air masses is observed at about 30° N. In contrast to the dominating trade wind regime with northeasterly winds, the ship cruise was mainly exposed to north-northwesterly winds with moderate weather conditions. In addition, the height of the atmospheric boundary layer is determined from the atmospheric profile, ranging from 500 m – 1700 m over open ocean. At coastal areas, especially at the Mauritanian upwelling, the boundary layer stays at the surface. For an evaluation of the wind measurements, wind speed and direction are compared to a high resolution ERA-Interim data set and, to NCEP/NCAR Reanalysis Project 1 Data (NNRP-1). In situ ship measurements show higher correlations for the wind speed (ERA-Interim: r = 0.91, NNRP-1: r = 0.79) than for the wind direction (ERA-Interim: r = 0.69, NNRP-1: r = 0.67). Recalculating the correlation coefficients for the same temporal resolution (6-hourly) results in an improvement of the correlations, indicating a good agreement between the observed and simulated wind. For the determination of potential source regions, the trajectory model HYSPLIT is used to investigate the origin of the observed air masses. The air mass history is analyzed 315 h backwards, indicating an air mass origin mainly above the North Atlantic during leg 2 but also above the Arctic Ocean during leg 3. During the 24 h stations close to the coast predominantly younger and local sources seem to influence the observed trace gas mixing ratios (mean CH2Br2/CHBr3 ratio: 0.4) with a partly strong dependency on the wind direction (r 〉 0.81). Especially the methyl iodide mixing ratios show a strong relation to air masses originating at the Banc d’Arguin National Park. In contrast to that, bromoform and dibromomethane show an increase of the mixing ratios connected to trajectories passing the coastal areas of Mauritania and Western Sahara. Increased mixing ratios of the observed trace gases concentrations with highest values of 8.9 ppt (bromoform), 3.31 ppt (dibromomethane) and 1.25 ppt (methyl iodide) are observed in combination with lowest boundary layer heights. With correlation coefficients of r = -0.90 (bromoform), r = -0.91 (dibromomethane) and r = -0.63 (methyl iodide) especially the mixing ratios of the longer lived bromocarbons seem to be strongly connected to the boundary layer height. However, the highest atmospheric bromoform mixing ratio of 9.8 ppt was not observed at the Mauritanian upwelling (leg 2), but close to Lisbon (leg 3) with the Rio Tejo as a potential source region. This implies the significance of regional sources as well as the consideration of the current lower atmospheric state for the variations of the VSLS mixing ratios

Description: Most of the short-lived biogenic and anthropogenic chemical species that are emitted into the atmosphere break down efficiently by reaction with OH and do not reach the stratosphere. Here we show the existence of a pronounced minimum in the tropospheric column of ozone over the West Pacific, the main source region for stratospheric air, and suggest a corresponding minimum of the tropospheric column of OH. This has the potential to amplify the impact of surface emissions on the stratospheric composition compared to the impact when assuming globally uniform OH conditions. Specifically, the role of emissions of biogenic halogenated species for the stratospheric halogen budget and the role of increasing emissions of SO2 in Southeast Asia or from minor volcanic eruptions for the increasing stratospheric aerosol loading need to be reassessed in light of these findings. This is also important since climate change will further modify OH abundances and emissions of halogenated species. Our study is based on ozone sonde measurements carried out during the TransBrom cruise with the RV Sonne roughly along 140-150 degrees E in October 2009 and corroborating ozone and OH measurements from satellites, aircraft campaigns and FTIR instruments. Model calculations with the GEOS-Chem Chemistry and Transport Model (CTM) and the ATLAS CTM are used to simulate the tropospheric OH distribution over the West Pacific and the transport pathways to the stratosphere. The potential effect of the OH minimum on species transported into the stratosphere is shown via modeling the transport and chemistry of CH2Br2 and SO2.

Description: Benthic nitrogen (N) cycling was investigated at six stations along a transect traversing the Peruvian oxygen minimum zone (OMZ) at 11 °S. An extensive dataset including porewater concentration profiles and in situ benthic fluxes of nitrate (NO3–), nitrite (NO2–) and ammonium (NH4+) was used to constrain a 1–D reaction–transport model designed to simulate and interpret the measured data at each station. Simulated rates of nitrification, denitrification, anammox and dissimilatory nitrate reduction to ammonium (DNRA) by filamentous large sulfur bacteria (e.g. Beggiatoa and Thioploca) were highly variable throughout the OMZ yet clear trends were discernible. On the shelf and upper slope (80 – 260 m water depth) where extensive areas of bacterial mats were present, DNRA dominated total N turnover (less-than-or-equals, slant 2.9 mmol N m–2 d–1) and accounted for greater-or-equal, slanted 65 % of NO3– + NO2– uptake by the sediments from the bottom water. Nonetheless, these sediments did not represent a major sink for dissolved inorganic nitrogen (DIN = NO3– + NO2– + NH4+) since DNRA reduces NO3– and, potentially NO2–, to NH4+. Consequently, the shelf and upper slope sediments were recycling sites for DIN due to relatively low rates of denitrification and high rates of ammonium release from DNRA and ammonification of organic matter. This finding contrasts with the current opinion that sediments underlying OMZs are a strong sink for DIN. Only at greater water depths (300 – 1000 m) did the sediments become a net sink for DIN. Here, denitrification was the major process (less-than-or-equals, slant 2 mmol N m–2 d–1) and removed 55 – 73 % of NO3– and NO2– taken up by the sediments, with DNRA and anammox accounting for the remaining fraction. Anammox was of minor importance on the shelf and upper slope yet contributed up to 62 % to total N2 production at the 1000 m station. The results indicate that the partitioning of oxidized N (NO3–, NO2–) into DNRA or denitrification is a key factor determining the role of marine sediments as DIN sinks or recycling sites. Consequently, high measured benthic uptake rates of oxidized N within OMZs do not necessarily indicate a loss of fixed N from the marine environment.

Description: Monthly zonal mean climatologies of atmospheric measurements from satellite instruments can have biases due to the non-uniform sampling of the atmosphere by the instruments. We characterize potential sampling biases in stratospheric trace gas climatologies of the Stratospheric Processes and their Role in Climate (SPARC) Data Initiative using chemical fields from a chemistry climate model simulation and sampling patterns from 16 satellite-borne instruments. The exercise is performed for the long-lived stratospheric trace gases O3 and H2O. Monthly sample biases for O3 exceed 10% for many instruments in the high latitude stratosphere and in the upper troposphere/lower stratosphere, while annual mean sampling biases reach values of up to 20% in the same regions for some instruments. Sampling biases for H2O are generally smaller than for O3, although still notable in the upper troposphere/lower stratosphere and Southern Hemisphere high latitudes. The most important mechanism leading to monthly sampling bias is the non-uniform temporal sampling of many instruments, i.e., the fact that for many instruments, monthly means are produced from measurements which span less than the full month in question. Similarly, annual mean sampling biases are well explained by non-uniformity in the month-to-month sampling by different instruments. Non-uniform sampling in latitude and longitude are shown to also lead to non-negligible sampling biases, which are most relevant for climatologies which are otherwise free of sampling biases due to non-uniform temporal sampling.

Description: The main purpose of R/V METEOR cruise M81/2AB was to obtain new insights into the controversially discussed origin and geodynamic evolution of the Caribbean Large Igneous Province (CLIP) and the Caribbean Plate using an interdisciplinary approach combining structural geology, geodynamics, magnetics, volcanology, sedimentology, petrology, magmatic geochemistry and geochronology. The rock sampling on M81/2AB achieved its major objectives through successful 1) stratigrafically-controlled sampling of a complete basement section of the northern Beata Rise with Kiel 6000 ROV (remote operated vehicle), 2) extensive dredge sampling of the southern Beata Rise, and 3) the first representative hard rock sampling of the Hess-Escarpment region. The wide range of intrusive, volcanic and sedimentary rocks recovered on M81/2AB represents the most detailed marine sampling of the CLIP and associated features to date. SIMRAD EM120 and PARASOUND were used to select sampling stations and to assess the structural geology of the region. Multi-beam seafloor mapping and preliminary analyses of the recovered samples suggest large-scale tectonic movements of the Beata Rise and the area north of the Hess-Escarpment and a volcanic rather than continental origin for the Nicaragua Rise north of the Hess-Escarpment. The magnetic studies were also highly successful with more than 7,300 km of magnetic profiles being acquired. Magnetic anomalies measured on four parallel profiles in the Colombia Basin suggest that the crust is oceanic, but seafloor spreading anomalies could not be correlated. Along the Hess Escarpment high amplitude magnetic anomalies associated with morphological features indicate a volcanic origin and basaltic composition of the crust, consistent with the seafloor morphology and recovered samples.

Description: Coccolithophores are a key functional group in terms of the pelagic production of calcium carbonate (calcite), although their contribution to shelf sea biogeochemistry, and how this relates to environmental conditions, is poorly constrained. Measurements of calcite production (CP) and coccolithophore abundance were made on the north-west European shelf to examine trends in coccolithophore calcification along natural gradients of carbonate chemistry, macronutrient availability and plankton composition. Similar measurements were also made in three bioassay experiments where nutrient (nitrate, phosphate) and pCO2 levels were manipulated. Nanoflagellates (〈 10 μm) dominated chlorophyll biomass and primary production (PP) at all but one sampling site, with CP ranging from 0.6 to 9.6 mmol C m−2 d−1. High CP and coccolithophore abundance occurred in a diatom bloom in fully mixed waters off Heligoland, but not in two distinct coccolithophore blooms in the central North Sea and Western English Channel. Coccolithophore abundance and CP showed no correlation with nutrient concentrations or ratios, while significant (p 〈 0.01) correlations between CP, cell-specific calcification (cell-CF) and irradiance in the water column highlighted how light availability exerts a strong control on pelagic CP. In the experimental bioassays, Emiliania-huxleyi-dominated coccolithophore communities in shelf waters (northern North Sea, Norwegian Trench) showed a strong response in terms of CP to combined nitrate and phosphate addition, mediated by changes in cell-CF and growth rates. In contrast, an offshore diverse coccolithophore community (Bay of Biscay) showed no response to nutrient addition, while light availability or mortality may have been more important in controlling this community. Sharp decreases in pH and a rough halving of calcite saturation states in the bioassay experiments led to decreased CP in the Bay of Biscay and northern North Sea, but not the Norwegian Trench. These decreases in CP were related to slowed growth rates in the bioassays at elevated pCO2 (750 μatm) relative to those in the ambient treatments. The combined results from our study highlight the variable coccolithophore responses to irradiance, nutrients and carbonate chemistry in north-west European shelf waters, which are mediated by changes in growth rates, cell-CF and species composition.

Description: Beschreibung:Discovery of novel natural products from soft corals were reported with many achievement so far. Soft coral associated bacteria have gained interest for several reasons such as for marine environmental protection and bio-mining of natural products from microorganism as compared to the animals. This work focused on communities of soft coral associated bacteria and on the search for new antimicrobial substances and new natural products as potential candidates for new drugs. Thus, soft coral associated bacteria were quite abundant and good sources of antimicrobial producers. The results from cultivation-based studies and sequence analysis of 16S rRNA genes of bacterial communities associated with the soft coral A. digitatum are reported in this study. A total of 251 isolates were identified as belonging to 4 phyla Firmicutes, Actinobacteria, Gammaproteobacteria, and Alphaproteobacteria. Four of these isolates may be new species, 2 isolates of Firmicutes, 1 Gammaproteobacterium and 1 Alphaproteobacterium. The high diversity of the bacterial communities and their antimicrobial activities suggest the contribution of the associated bacteria to the coral health. The results from antimicrobial tests demonstrated that A. digitatum was the source of various bacteria producing antimicrobial substances. Antimicrobial activity of the isolates were found only in BM medium (3%), only in GYM medium (2%) or in both of these media (44%). Quite significant, all isolates belonging to the two species B. amyloliquefaciens and B. methylotrophicus showed antimicrobial activities. Some strains of the two species inhibited all four test microorganisms. Chemical analyis revealed that the two Bacillus sp. strains produced various known cyclic peptides as well as presumably new metabolites. They represented highly potent producers of antimicrobials. All isolates of Actinobacteria produced antimicrobial substances, that inhibited particulary Gram-positive bacteria. In addition to a marine Micrococcus isolate, three isolates of Firmicutes were thoroughly studied in regard to analysis of production of new compounds. In addition a number of known compounds were identified, including several peptides. The metabolites of the four strains were examined and purified by using several HPLC systems. The biological activities of pure compounds were studied using antibacterial, antifungal, cytotoxic, and enzyme assays. Eleven compounds were purified and applied to bioassays. One of the proposed known cyclic peptides showed antimicrobial activity against both B. subtilis and E. coli, whereas the others showed inhibition of methicillin-resistant Staphylococcus aureus (MRSA) and phosphodiesterase 4β2. One of compounds, which were considered as new compounds, inhibited fungus Trichophyton rubrum and enzyme phosphodiesterase 4β2. The structure elucidations of all pure compounds are in progress.  

Description: We focus on the relation between seismic and total postseismic afterslip following the Maule Mw 8.8 earthquake on 2010 February 27 in central Chile. First, we calculate the cumulative slip released by aftershock seismicity. We do this by summing up the aftershock regions and slip estimated from scaling relations. Comparing the cumulative seismic slip with afterslip models we show that seismic slip of individual aftershocks exceeds locally the inverted afterslip model from geodetic constraints. As the afterslip model implicitly contains the displacements from the aftershocks, this reflects the tendency of afterslip models to smear out the actual slip pattern. However, it also suggests that locally slip for a number of the larger aftershocks exceeds the aseismic slip in spite of the fact that the total equivalent moment of the afterslip exceeds the cumulative moment of aftershocks by a large factor. This effect, seen weakly for the Maule 2010 and also for the Tohoku 2011 earthquake, can be explained by taking into account the uncertainties of the seismicity and afterslip models. In spite of uncertainties, the hypocentral region of the Nias 2005 earthquake is suggested to release a large fraction of moment almost purely seismically. Therefore, these aftershocks are not driven solely by the afterslip but instead their slip areas have probably been stressed by interseismic loading and the mainshock rupture. In a second step, we divide the megathrust of the Maule 2010 rupture into discrete cells and count the number of aftershocks that occur within 50 km of the centre of each cell as a function of time. We then compare this number to a time-dependent afterslip model by defining the ‘afterslip to aftershock ratio’ (ASAR) for each cell as the slope of the best fitting line when the afterslip at time t is plotted against aftershock count. Although we find a linear relation between afterslip and aftershocks for most cells, there is significant variability in ASAR in both the downdip and along-strike directions of the megathrust. We compare the spatial distribution of ASAR with the spatial distribution of seismic coupling, coseismic slip and Bouguer gravity anomaly, and in each case we find no significant correlation.

Description: Dates of the cruise: 04.06.2014 to 19.06.2014

Description: An vier Tidenzyklus-Stationen von 21 bis 36 Std. Dauer wurde auf einem Längsschnitt von Hamburg bis zur Außenelbe untersucht, welchen Anteil die Bakterien am Abbau der organischen Substanz haben. Der Gesamt-Abbau durch die planktische Organismengemeinschaft wurde aus dem Sauerstoffverbrauch mit einem angenommenen Respirationsquotienten von 0,85 bestimmt. Der bakterielle Abbau wurde über die Biomasse-Produktion und die Wachstums-Effizienz der Bakterien ermittelt. Die Tidenzyklus-Stationen mit einer hohen zeitlichen Auflösung zeigten eine große Variabilität der Abbauprozesse während der Gezeiten. Die Mittelwerte ergaben, dass der Gesamt-Abbau im oberen noch limnischen Bereich 10,2 μg C l-1 h-1 betrug mit einem bakteriellen Anteil von 82%. Flussabwärts ging der Gesamt-Abbau auf 2,7 μg C l-1 h-1 zurück und der bakterielle Anteil belief sich auf rd. 50 %. Der Längsschnitt von Hamburg bis Neuwerk mit einer hohen räumlichen Auflösung zeigte eine grundsätzlich ähnliche regionale Verteilung. Der hohe Anteil des bakteriellen Abbaus in dem oberen limnischen Ästuarbereich geht darauf zurück, dass das hier aus dem Mittellauf der Elbe eingeschwemmte Phytoplankton infolge Lichtmangels größtenteils abstirbt. Die Ursachen liegen in der großen Wassertiefe des Hamburger Hafengebietes und der starken Gezeitendurchmischung der Wassersäule. Dadurch vermindert sich die Respiration des Phytoplanktons und die Abbautätigkeit ist daher im Wesentlichen auf die Bakterien und das Zooplankton beschränkt. Von diesen beiden verbleibenden Hauptkomponenten des Flussplanktons spielen die Bakterien die wichtigere Rolle beim Abbau der organischen Substanz im Elbe-Ästuar.

Description: Sea surface and atmospheric measurements of dimethylsulphide (DMS) were performed during the TransBrom cruise in the western Pacific Ocean between Japan and Australia in October 2009. Air–sea DMS fluxes were computed between 0 and 30 μmol m−2 d−1, which are in agreement with those computed by the current climatology, and peak emissions of marine DMS into the atmosphere were found during the occurrence of tropical storm systems. Atmospheric variability in DMS, however, did not follow that of the computed fluxes and was more related to atmospheric transport processes. The computed emissions were used as input fields for the Lagrangian dispersion model FLEXPART, which was set up with actual meteorological fields from ERA-Interim data and different chemical lifetimes of DMS. A comparison with aircraft in situ data from the adjacent HIPPO2 campaign revealed an overall good agreement between modelled versus observed DMS profiles over the tropical western Pacific Ocean. Based on observed DMS emissions and meteorological fields along the cruise track, the model projected that up to 30 g S per month in the form of DMS, emitted from an area of 6 × 104 m2, can be transported above 17 km. This surprisingly large DMS entrainment into the stratosphere is disproportionate to the regional extent of the area of emissions and mainly due to the high convective activity in this region as simulated by the transport model. Thus, if DMS can cross the tropical tropopause layer (TTL), we suggest that the considerably larger area of the tropical western Pacific Ocean can be a source of sulphur to the stratosphere, which has not been considered as yet.

Description: At the Uruguayan continental margin, seismic evidence for the occurrence of gas hydrate has been identified based on the presence of BSRs in densely spaced 2D reflection seismic sections from different surveys. Mapping of BSRs based on 2D seismic data acquired in 2007 and 2008 suggested the presence of gas hydrates in areas that were not previously identified; hence hydrate occurrence offshore Uruguay is more widespread than previously thought. Recently ANCAP has digitized offshore seismic data acquired between 1970 and 1982. Being able to work on this data using interpretation software, and integrating results with the latest interpretations performed on the seismic collected in 2007 and 2008, the BSR extends over an area of approximately 25.000 km2. It is present in water depths greater than 500 m and has high continuity in Pelotas Basin but is more discontinuous at Punta del Este Basin and southern part of Oriental del Plata Basin. In offshore basins around the world the base of GHSZ can have different seismic expressions such as continuous, segmented, and high-relief BSRs depending on the stratigraphic, fluid and geothermal setting. Here, we present examples of the influence of the acquisition parameters on the acoustic expression of the BSR, comparing commercial seismic sections acquired for hydrocarbon exploration and high resolution seismic sections acquired during the R/V Meteor Cruise M49/2 in 2001 and R/V Meteor Cruise M78/3a (May - June 2009) using different sources and streamer system. For the different data sets the BSR presents differences regarding its continuity and amplitude strength. In high resolution seismic, enhanced amplitudes and phase reversals are observed for several reflectors while deep penetration seismic shows only one single continuous reflector. This comparison may help to visualize the complexity of the free gas, gas hydrate and stratigraphic system behind the BSR, which is usually masked on low-frequency deep penetration seismic data.

Description: Methyl iodide (CH3I}, bromoform (CHBr3) and dibromomethane (CH2Br2), which are produced naturally in the oceans, take part in ozone chemistry both in the troposphere and the stratosphere. The significance of oceanic upwelling regions for emissions of these trace gases in the global context is still uncertain although they have been identified as important source regions. To better quantify the role of upwelling areas in current and future climate, this paper analyzes major factors that influenced halocarbon emissions from the tropical North East Atlantic including the Mauritanian upwelling during the DRIVE expedition. Diel and regional variability of oceanic and atmospheric CH3I, CHBr3 and CH2Br2 was determined along with biological and meteorological parameters at six 24 h-stations. Low oceanic concentrations of CH3I from 0.1–5.4 pmol L-1 were equally distributed throughout the investigation area. CHBr3 of 1.0–42.4 pmol L-1 and CH2Br2 of 1.0–9.4 pmol L-1 were measured with maximum concentrations close to the Mauritanian coast. Atmospheric mixing rations of CH3I of up to 3.3, CHBr3 to 8.9 and CH2Br2 to 3.1 ppt above the upwelling and 1.8, 12.8, respectively 2.2 ppt at a Cape Verdean coast were detected during the campaign. While diel variability in CH3I emissions could be mainly ascribed to oceanic non-biological production, no main driver was identified for its emissions in the entire study region. In contrast, oceanic bromocarbons resulted from biogenic sources which were identified as regional drivers of their sea-to-air fluxes. The diel impact of wind speed on bromocarbon emissions increased with decreasing distance to the coast. The height of the marine atmospheric boundary layer (MABL) was determined as an additional factor influencing halocarbon emissions. Oceanic and atmospheric halocarbons correlated well in the study region and in combination with high oceanic CH3I, CHBr3 and CH2Br2 concentrations, local hot spots of atmospheric halocarbons could solely be explained by marine sources. This conclusion is in contrast with previous studies that hypothesized the occurrence of elevated atmospheric halocarbons over the eastern tropical Atlantic mainly originating from the West-African continent.

Description: Calcium carbonates (CaCO32-­‐) belong to the most common mineral groups within the marine realm. In this thesis interactions between marine microbes and carbonate stability are investigated in depth. Microbial biofilms are analyzed at high resolution regarding their functions in element and isotopic fractionation. In addition, calcite dissolution experiments were carried out to quantify the effect of aerobic methane oxidizing bacteria. Carbonate precipitation rates in marine sediments often serve as a fitting parameter for numerical modeling approaches to constrain. 45Ca and 14C-bicarbonate incubation experiments were carried out to quantify ongoing calcification in natural sediment slurries. During a research cruise rates of anaerobic methane oxidation and sulfate reduction were determined for the first time using radiotracers. The obtained rates were combined with carbonate isotopic signatures to elucidate local variations of fluid advection.

Description: Marine sediments all over the world bear methane, generated from organic matter and deposited at the seafloor. By diffusion or ascending fluids the methane is transported to the sediment surface and emitted into the oceans and further into the atmosphere, where it acts as greenhouse gas. However, most of the methane is anaerobically or aerobically oxidized by microbes in the upper sediments and in the water column. One of the most important methane oxidizing processes is the anaerobic oxidation of methane (AOM) in the microbial benthic methane filter. Consortia of anaerobic methanotroph (ANME) archeae and sulfate reducing bacteria (SRB) consume the methane with sulfate as final electron acceptor. While the methane is delivered from deeper reservoirs, sulfate originates from the seawater and has to diffuse into the sediment. AOM occurs mainly in the intersection of sulfate and methane, the sulfate methane transition zone (SMTZ). At continental margins gas hydrate bearing sediments form huge reservoirs of methane. Methane can be transported by upward migrating fluids from dewatered and dehydrated sediments. At the sediment surface, advecting fluids form so called “cold seeps”. The microbial benthic methane filter of cold seeps is well established and adapted to the flow conditions. However, increasing fluid flux can challenge the microbial benthic filter by higher methane flux and lower sulfate penetration depth, by resulted higher methane emissions. The aim of this thesis is to study efficiency and adaptability of the benthic methane filter under non-steady state conditions. For this purpose I developed a sediment flow-through (SLOT) system to mimic the fluid regime of the benthic methane filter and to monitor long-term incubations of undisturbed sediment cores from cold seeps under varying fluid fluxes. All experiments were performed under anoxic conditions and with two parallel sediments cores under varying fluid flow conditions. The presented thesis combines field data and experimental data from sediments of different cold seep sites and their microbial benthic methane filter. First experiments with coastal gassy sediments from Eckernförde Bay constrain the possibility of SLOT to simulate fluid flow regimes of microbial benthic filters under fluid flux differences of one magnitude. Additionally, other seep related processes such as sulfide oxidation and precipitation were observed and prove the usefulness of the SLOT system for biogeochemical studies. Two neighboring mounds with different steady state conditions were studied offshore Costa Rica. These mounds differ in fluid source, fluid flux as well as methane flux. Both mounds exhibit a well established microbial benthic filter which is adapted to their respective flow conditions. Fluid and methane source are reflected in the isotopic signature of authigenic carbonates, which are the archive of cold seep systems. Field and experimental data from the Quepos Slide offshore Costa Rica were combined to study the benthic methane filter. In the experiments the microbial benthic methane filter was highly efficient and shows a good adaption within 150-170 d response time with low methane efflux within the transition. A fluid pulse with higher methane emissions reveals how fast the methane efflux can change when fluid flux is increased. Furthermore, three different cold seep habitats from a recently discovered cold seep area at the continental margin of Chile were studied. Experiments with a bacterial mat habitat from a young seep site show a uniform fluid flow through the sediment and reveal a high adaptability of the benthic methane filter. In a clam field with high sulfide production an enormous methane efflux occured before the benthic filter was adapted to the new fluid regime. In sediments with an aerobic benthic methane filter from a tubeworm habitat, fluids were channeled by biogenic tubes. The benthic methane filter changed during the 150 d of anoxic incubation from an aerobic to an anaerobic methane sink. In the present thesis it is demonstrated for the first time how enthic methane filters adapt to increased fluid flux. The studies reveal that beside preconditions and the intensity of the variation the sediment matrix flow conditions through the sediment is prime important for the adaptability of the benthic methane filter.

Description: Oceanic emissions of halogenated very short-lived substances (VSLS) are expected to contribute significantly to the stratospheric halogen loading and therefore to ozone depletion. The amount of VSLS transported into the stratosphere is estimated based on in-situ observations around the tropical tropopause layer (TTL) and on modeling studies which mostly use prescribed global emission scenarios to reproduce observed atmospheric concentrations. In addition to upper-air VSLS measurements, direct observations of oceanic VSLS emissions are available along ship cruise tracks. Here we use such in-situ observations of VSLS emissions from the West Pacific and tropical Atlantic together with an atmospheric Lagrangian transport model to estimate the direct contribution of bromoform (CHBr3), and dibromomethane (CH2Br2) to the stratospheric bromine loading as well as their ozone depletion potential. Our emission-based estimates of VSLS profiles are compared to upper-air observations and thus link observed oceanic emissions and in situ TTL measurements. This comparison determines how VSLS emissions and transport in the cruise track regions contribute to global upper-air VSLS estimates. The West Pacific emission-based profiles and the global upper-air observations of CHBr3 show a relatively good agreement indicating that emissions from the West Pacific provide an average contribution to the global CHBr3 budget. The tropical Atlantic, although also being a CHBr3 source region, is of less importance for global upper-air CHBr3 estimates as revealed by the small emission-based abundances in the TTL. Western Pacific CH2Br2 emission-based estimates are considerably smaller than upper-air observations as a result of the relatively low sea-to-air flux found in the West Pacific. Together, CHBr3 and CH2Br2 emissions from the West Pacific are projected to contribute to the stratospheric bromine budget with 0.4 pptv Br on average and 2.3 pptv Br for cases of maximum emissions through product and source gas injection. These relatively low estimates reveal that the tropical West Pacific, although characterized by strong convective transport, might overall contribute less VSLS to the stratospheric bromine budget than other regions as a result of only low CH2Br2 and moderate CHBr3 oceanic emissions.

Description: This diploma thesis discusses the effect of clouds under arctic conditions on the energy balance at ground and the impact on sea ice and snow conditions. To calculate the energy balance is used an one-dimensional sea ice model from Andreas Lehmann. He is a scientist at the IFM-GEOMAR in the field of research „theory and modelling “. The model for this thesis is taken from the threedimensional and dynamic ice model BSIOM(Jacob et al. (2006)). The energy balance is made up of incoming solar radiation with the surface albedo, the outgoing and incoming longwave radiation and the latent and sensible heat flux. The radiation flux dominate the energy balance in the Arctic. Therefore at first several parameterizations for incoming shortwave radiation and longwave counter-radiation are analysed with data from the expedition ARK-XXIV/3 of the research vessel Polarstern. For the analysis are put parameterizations for the global radiation from Zillman (1972), Shine (1984), Bennett (1982) and Shine/Bennett. Parameterizations by Maykut und Church (1973), Zillman (1972), König-Langlo und Augstein (1994), Konzelmann et al. (1994) and Zapadka et al. (2007) are used for the study of the longwave counter-radiation. The parameterizations of shortwave radiation can reflect the rough diurnal variations in global radiation. Nevertheless, there are considerable differences between observation and parameterization, if direct sunlight arrives ground under a high degree of cloud cover and it comes to short-term increase in radiation. These increases can not be reproduced by any of the parameterizations. In principle, the parameterizations tend to overestimate low values of shortwave radiation and to underestimate high values. The parameterizations of longwave counter-radiation have significant problems to reflect the diurnal variation of the measured values on some days. Especially after sunrise and before sunset are often the coverages of clouds from the cloud detection algorithms be misinterpreted on the sky imager photos. In these cases the differences between the values of parameterization and observation can be more than 100 W/m2. The analyses of the calculated energy balances with the one-dimensional sea ice model for three locations in the Arctic in the years 2006 to 2009 shows that clouds have a major influence on the radiation balance. Therefore several sensitivity studies are carried out. The sea ice and snow change under different cloud conditions, thus the surface albedo varies. Clouds effect a weakening of shortwave radiation in the Arctic summer. However they provide an all-season increase in longwave counter-radiation. The longwave radiation dominates the energy balance at ground in the Arctic, which is reflected in the model results of the ice thickness. The sea ice is thicker at the end of the year in case of an all-season cloudless sky as a continuous covered sky.

Description: Emissions of halogenated very short-lived substances (VSLS) are poorly constrained. However, their inclusion in global models is required to simulate a realistic inorganic bromine (Bry) loading in both the troposphere, where bromine chemistry perturbs global oxidizing capacity, and in the stratosphere, where it is a major sink for ozone (O3). We have performed simulations using a 3-D chemical transport model (CTM) including three top-down and a single bottom-up derived emission inventory of the major brominated VSLS bromoform (CHBr3) and dibromomethane (CH2Br2). We perform the first concerted evaluation of these inventories, comparing both the magnitude and spatial distribution of emissions. For a quantitative evaluation of each inventory, model output is compared with independent long-term observations at National Oceanic and Atmospheric Administration (NOAA) ground-based stations and with aircraft observations made during the NSF HIAPER Pole-to-Pole Observations (HIPPO) project. For CHBr3, the mean absolute deviation between model and surface observation ranges from 0.22 (38%) to 0.78 (115%) parts per trillion (ppt) in the tropics, depending on emission inventory. For CH2Br2, the range is 0.17 (24%) to 1.25 (167%) ppt. We also use aircraft observations made during the 2011 "Stratospheric Ozone: Halogen Impacts in a Varying Atmosphere" (SHIVA) campaign, in the tropical West Pacific. Here, the performance of the various inventories also varies significantly, but overall the CTM is able to reproduce observed CHBr3 well in the free troposphere using an inventory based on observed sea-to-air fluxes. Finally, we identify the range of uncertainty associated with these VSLS emission inventories on stratospheric bromine loading due to VSLS (BryVSLS). Our simulations show BryVSLS ranges from ~ 4.0 to 8.0 ppt depending on the inventory. We report an optimised estimate at the lower end of this range (~ 4 ppt) based on combining the CHBr3 and CH2Br2 inventories which give best agreement with the compilation of observations in the tropics.

Description: The main goal of MSM21/4 was the study of gas hydrate system off Svalbard. We addressed this through a comprehensive scientific programme comprising dives with the manned submersible JAGO, seismic and heat flow measurements, sediment coring, water column biogeochemistry and bathymetric mapping. At the interception of the Knipovich Ridge and the continental margin of Svalbard we collected seismic data and four heat flow measurements. These measurements revealed that the extent of hydrates is significantly larger than previously thought and that the gas hydrate system is influenced by heat from the oceanic spreading centre, which may promote thermogenic methane production and thus explain the large extent of hydrates. At the landward termination of the hydrate stability zone we investigated the mechanisms that lead to degassing by taking sediment cores, sampling of carbonates during dives, and measuring the methane turn-over rates in the water column. It turned out that the observed gas seepage must have been ongoing for a long time and that decadal scale warming is an unlikely explanation for the observed seeps. Instead seasonal variations in water temperatures seem to control episodic hydrate formation and dissociation explaining the location of the observed seeps. The water column above the gas flares is rich in methane and methanotrophic microorganisms turning over most of the methane that escapes from the sea floor. We also surveyed large, until then uncharted parts of the margin in the northern part of the gas hydrate province. Here, we discovered an almost 40 km wide submarine landslide complex. This slide is unusual in the sense that it is not located at the mouth of a cross shelf trough such as other submarine landslides on the glaciated continental margins around the North Atlantic. Thus, the most widely accepted explanation for the origin of such slides, i.e. overpressure development due to deposition of glacial sediments on top of water rich contourites, is not applicable. Instead we find gas-hydrate-related bottom simulating reflectors underneath the headwalls of this slide complex, possibly indicating that subsurface fluid migration plays a major role in its genesis.

Description: Within the Jeddah Transect Project, a multidisciplinary marine sampling program has been performed on RV Poseidon (P408 cruise) offshore Saudi-Arabia (Red Sea). The sampling program involved three projects (http://www.ifm-geomar.de/index.php?id=jeddahtransectdisc&L=1), covering aspects of marine petrology, biogeochemistry, oceanography and biology.

Description: The DRIVE (Diurnal and RegIonal Variability of Halogen Emissions) campaign to the eastern tropical North Atlantic Ocean and the upwelling off Mauritania (NW Africa) was funded by the BMBF as part of the German SOLAS project SOPRAN II (Surface Ocean Processes in the Anthropocene; www.sopran.pangaea.de): The second leg of the 399th cruise of R/V Poseidon (P399/2) took place from 31 May to 17 June 2010 (Las Palmas-Mindelo (Cape Verde Islands) – Mauritanian upwelling – Las Palmas). It was followed by the transit leg 3 (P399/3) which took place from 18 June to 24 June 2010 (Las Palmas – Vigo (Spain)) with only one stop at ESTOC. Ten scientists from IFM-GEOMAR (Kiel), IfAM (U Kiel), IfBM (U Hamburg) and IUP (U Heidelberg) representing various SOPRAN II subprojects took part in the cruise which was the sixth of a series of German SOLAS cruises to the tropical North Atlantic Ocean. The major objective of P399/2 was to investigate the regional and diurnal atmospheric and oceanic variations of halogenated compounds in the eastern tropical North Atlantic Ocean with a special focus on the Mauritanian upwelling. The main working packages of P399/2 and P399/3 included measurements of - Atmospheric BrO and IO - Atmospheric halocarbons - Other atmospheric trace gases such as ozone, methane etc. - Aerosol composition - Vertical structure of the atmosphere - Dissolved halocarbons, nitrous oxide and carbon dioxide - CTD, dissolved nutrients, O2, and chlorophyll - Microstructure of the upper water column Besides an extensive underway measurement program of dissolved (halocarbons, N2O, CO2) and atmospheric (BrO, halocarbons, other trace gases, aerosol) compounds, six 24h stations were performed and 23 regular CTD stations with depth profiles covering the entire water column were occupied.

Description: The evolution from the Western Mediterranean Sea is inherently governed by (i) plate convergence between Nubia (Africa) / Eurasia and (ii) subduction related slab-roll back. Both processes are responsible for the surface features / topography of the Gulf of Cadiz / Gibraltar Arc / Alboran Sea / Rif / Betic domain and deep-seated features related to the consumption of African lithosphere. The project is part of the ESF-EUROCORES programme TOPO-EUROPE and is aiming to study the interrelation between convergence and major tectonic fault zones in the Gulf of Cadiz and the Alboran Sea (Trans-Alboran- Shear-Zone – Alboran Ridge) and Miocene subduction / deep-seated seismicity at 40-150 km depth. Monitoring networks with ocean bottom seismometers (OBS) and hydrophones (OBH) were installed first in the Alboran Sea (August 2009 to January 2010) and later in the Gulf of Cadiz (January 2010 to July 2010), providing for the first time local earthquake data collected on ocean bottom stations. First results suggest that the collected data are of every good quality to assess seismotectonics in both domains and yielding travel time data for unique tomographic images of the Gibraltar arc area and Alboran domain, providing seismic constraints on the structure of crust and mantle.

Description: RV Sonne cruise 206 started on the 31st of May in Caldera (Costa Rica) and ended there on the 18th of June 2010. An international group of 23 scientists and 2 guests from Costa Rica set out to perform geophysical, biogeochemical, and sedimentological investigations at and around a number of submarine cold seeps that are ubiquitous along this convergent continental margin. The cruise was predominantly conducted as a pre-site survey for IODP (proposal 633Full-2; Costa Rica Mounds) in order to fill existing gaps in the seismic record at two of the proposed drill locations. A 2D seismic survey was conducted running over the large-scale seamount subduction slide “Jaco Scarp” yielding a highly improved image of the structural pattern within the upper 1000 m of the sedimentary sequence. In addition, high-resolution 3D seismic data, roughly covering the uppermost 300 m, could be obtained in the Mound 11/12 area, which will allow for a detailed analysis of the internal structure of these mud volcano-like features and help to understand the complex relation to the upward directed material flow. Moreover, a total number of 36 sediment cores (TV-guided multicorer, gravity corer) were successfully retrieved from active cold seeps and submarine slides and a large number of sub-samples were taken for subsequent geochemical and microbiological analyses. Overall, all major tasks of this cruise could successfully be fulfilled and the results will help to further our understanding of mechanisms controlling fluid flow in the deep subsurface of active continental margins.

Description: The research project SO208 PLUMEFLUX (Propagation of Galápagos Plume Material in the Equatorial East Pacific) is funded by the German Ministry of Education and Research (BMBF) and focusses on seamounts on the Cocos Plate, formed at the East Pacific Rise but presently located off the coast of NW Costa Rica and Nicaragua (Leg 1), and on the Cocos-Nazca-Spreading Center(CNS; Leg 2). The studies conducted on cruise SO208 included multi-beam mapping, sediment echo sounding, hard rock sampling, as well as sedimentological and biological sampling. The major geological targets of Leg 1 were (1) to evaluate if the seamounts off northern Costa Rica and Nicaragua were formed by the Galápagos hotspot and thus to constrain the extent of influence by the Galápagos plume on the upper asthenosphere and lithosphere and (2) to constrain better the material input into the Central American subduction zone. Leg 2 aimed to sample profiles of the seafloor perpendicular to the CNS using the mobile drill Rockdrill 2 of the British Geological Survey, in order to reconstruct plume-ridge interaction in the past to complement morphological, petrological and geochemical studies carried out on previous cruises along the ridge axis (e.g. SO158). The integration of the results with existing data should contribute towards a better understanding of transport processes of plume material in the upper mantle and of the geodynamic evolution of the central East Pacific. The sedimentological studies carried out on both Legs of SO208 focussed on radiolarian assemblages. SO208 startet in Caldera/Costa Rica on July 15th, 2010, and ended in Guayaquil/Ecuador on August 29th, 2010. During Leg 1 nineteen seamounts on the Cocos Plate have been mapped and sampled. Within only 12 days at sea, a total of 41 stations(28 dredges, 2 TV grabs, and 11 multicorers) were carried out. Of these deployments, 23 recovered magmatic rocks, 15 volcaniclastics, and 13 Mn-Fe oxides. The samples comprise mainly pillow and sheet lavas, often with fresh glassy margins, and a wide spectrum of volcaniclastic rocks. Notably, we found several indications for explosive volcanic activity at water depths 〉 3,000 m. Due to a series of unfortunate circumstances beyond our control, the planned Rockdrill 2 deployment on Leg 2 had to be cancelled. Instead we mapped and collected samples via dredging from 60 localities along five profiles perpendicular to CNS. A total of 83 stations (76 dredges, 3 TVgrabs, and 4 multicorers) were carried out. Of these deployments, 59 recovered magmatic rocks, 3 volcaniclastics, 51 volcanic glass, and 6 Mn-Fe oxides, making this a successful cruise despite the Rockdrill problem. The first and most detailed profile (with 23 sampled localities) extended from the ridge axis to the north at ~92°W. The morphology shows alternating regions of abyssal ridges and valleys (possibly reflecting less plume input into the ridge) and thicker elevated bands commonly containing seamounts, some of which are tectonically deformed (possibly reflecting axial ridge type morphology and thus greater plume input into the ridge). The second profile was carried out at the shallowest part of the ridge axis, closest to the hotspot, just to the east of the 91° Transform Fault. The third profile extended 30 km north of the ridge (at ~89°30´W), where a formerly on-axis seamount has been split in half. We want to evaluate how far in the past the unique enriched geochemical anomaly associated with the seamount persisted in the past. Thirteen sites were successfully sampled along a fourth profile at 89°10’W, extending 35 km north and 35 km south of the CNS into crust up to 500,000 yrs old. This site was selected, because a major depleted geochemical anomaly exists at that location. A final short profile was carried out to the north and south and east (on the ridge axis) of a lava plateau at 88°20’W that represents an enriched anomaly along the ridge axis. The morphology of the area studied on Leg 2 strongly suggests that the intensity of interaction of the plume with the ridge has varied considerably over the last several hundred thousand years along the entire part of the ridge that we studied. Geochemical data should allow us to constrain better variations in plume-ridge interaction through time. Biological material was obtained successfully as macrofauna and as sediment samples containing meiofaunal organisms with the help of a geological chain bag dredge, sediment traps, a multicorer and a TV-grab. Macrofaunal organisms were recovered at 93 out of 124 stations, 37 stations revealed sediment samples. During the cruise, a total of 8,598 meiofaunal organisms were centrifuged out of about 45 kg of sediment and sorted to animal group. Foraminifera and Nematoda dominated the meiofauna, followed by Copepoda and at a lower abundance by Tardigrada, Kinorhyncha and Loricifera. We also discovered a highly diverse benthic macrofauna, mainly represented by Porifera, Bryozoa, Annelida, Brachiopoda and even a few monoplacophoran molluscs.

Description: Cruise SO210 with RV SONNE to the active continental margin off Chile was conducted by shiptime exchange with RV METEOR. Funds for mobilizing the research team were provided by the German Science Foundation (DFG) in conjunction with the Collaborative Research Centre (SFB) 574 of the University of Kiel. In the first years, the SFB 574 investigated the pathways and fluxes of volatiles through the erosive subduction zone off Central America. For comparison, the studies were extended to the accretionary margin off Central Chile. Cruise SO210 is the last cruise conducted in the framework of SFB 574 and based on investigations of previous SFB-cruises on the RVs VIDAL GORMAZ and JAMES COOK. The first leg of cruise SO210 was dedicated to long gravity coring for volcanic ash layers from the erruptive Southern Volcanic Zone (SVZ) of the Andes that were either deposited as fallouts onto the incoming Nazca Plate or transported down the slope and across the Chile Trench. Eight gravity cores of 12 m length were retrieved seaward of the Chile Channel on the outer rise of the Nazca Plate. The second goal for coring was the description and dating of previously mapped submarine landslides as well as retrieval of slide-related material for geo-technical experiments. As the deployment frame for long coring had to be removed on the second leg we continued coring for mass-wasting and geochemistry with short cores. Ten gravity cores of 3 or 6 m barrel length were retrieved upslope of slides, the glide plane and redeposited material downslope of the slide evacuation area. This sampling activity was supported by detailed acoustic surveys with Parasound and multibeam to remap critical areas for mass wasting in search for events, e.g. triggered by the recent Mw 8.8 Maule Earthquake, such as flanks of submarine canyons or previously detected submarine slides and to fill data gaps in the existing bathymetric data. The major activity of the entire cruise was dedicated to the search and detailed sampling of manifestations of fluid discharge activity on the Chilean forearc. A total of 11 deployments with the video sled OFOS and 12 dives by the ROV KIEL 6000 were conducted for ground-truthing of information which indicated possible seep activity and has been obtained during previous cruises to the Chilean forearc. In five working areas we found manifestations of fluid discharge. In these areas the survey was followed by an intense sampling of bottom water, sediments, carbonates, mega and meiofauna and the deployment of instrumentation on the seafloor. The goal of these deployments was to measure in situ seabed methane emission rates and associated fluxes of sulfide and major electron acceptors such as oxygen at seep sites along the Chilean margin and to understand its controls. This was accompanied by CTD casts to trace oxygen and the fate of methane discharge in the water column. Sediment cores obtained by multicorer or ROV were used for the geochemical characterization of the pore water and microbiological studies which include turnover rate measurements, molecular studies, flow through experiments and sampling of active sediments. Authigenic carbonates obtained by TV-Grab or ROV were sampled for fauna, biomarker studies and investigations to reconstruct the growth structures, calcification processes and fluid-pathway systematic. The sampling of sediments and carbonates recovered a unique fauna with 79 different taxa, several of them appear to be species new to science.

Description: Cruise SO-214 of R/V SONNE headed by IFM-GEOMAR served two legs of project NEMESYS, funded through the German Ministry of Education and Research (BMBF). Major partners of the project are Leibniz Institute of Marine Science (IFM-GEOMAR) and the Federal Institute of Geosciences and Natural Resources (BGR) Germany, as well as the Institute of Geological and Nuclear Sciences (GNS) and the Royal Netherlands Institute for Sea Research (NIOZ). NEMESYS aims to extend understanding and modelling of cold vents along the Hikurangi Margin (HM) off the east coast of the North Island of New Zealand. Since the first findings in the late 80´s several cruises have been dedicated to map and investigate the active seepage of Methane in this area. Results of these cruises headed by New Zealand and international scientists provided the database for the first joint German – New Zealand expedition SO-191 in 2007. During this cruise with R/V SONNE the HM was investigated within three legs comprising all marine geo-scientific disciplines. The major findings in geophysical, geological, geo-chemical, and biological research were published in a special issue by Marine Geology (Vol. 272, 2010). Nevertheless a lot of questions remained or were raised by the upcoming results. Still lateral continuation of feeder channels and a possible relation between internal structure, activity and tectonic regime of a seep site were not understood. The geological, geo-chemical and biological analysis has been related to the overall description and study of the seep sites along the margin. Detailed studies across a seep site and high-resolution sampling to study the internal variation of Methane production and the influences to chemistry and habitat have not been complete with the required intensity. These exemplary listed investigations together with an additional list of questions to seepage led to the follow-up project SO-214 NEMESYS, which was funded through the German Ministry of Education and Research (BMBF). Aim of the project NEMESYS is to confirm derived models of seep structures and to extend the existing database and knowledge by high-resolution sampling in all disciplines. Based on the findings of the SO-191 New Vents project Opouawe Bank and Omakere Ridge were identified as the areas with the highest interest for our additional studies. Opouawe Bank provides a high density of active seep sites with various expressions of feeder channels in seismic images. Omakere did provide the only seep sites that were found without feeder channels underneath. In between the Porangahau Ridge was selected as third target due to the indications of either gas or hydrate formation without active gas expulsion. Cruise SO-214 with R/V SONNE was split into two legs. The seismic part started on 09th March 2011 in the port of Wellington. Two 3D seismic cubes were acquired above active seep sites at Omakere and Opouawe Bank. A third cube at Porangahau Ridge could not be completed due to technical problems with the equipment and rough weather conditions. Intensive Parasound Profiling and extended 2D seismic with high resolution (up to 1.2 m migration grid) were undertaken. Many more feeder channels were identified than previously known from the SO-191 data, although not all of them terminate in a seafloor expression. The second leg left the port of Wellington on 6th April 2011 dedicated to intensive geological, geo-chemical and biological investigations. The major work was completed at Opouawe Bank. Based on images of the seismic data compilation North and South Tower seeps and seep site Takahe were chosen for the intensive sampling program. CTD and gravity cores were taken in dense spacing to investigate the local interaction of seepage and surrounding seafloor and water column. The water column showed limited stratification but seemed to be influenced from stormy weather. Biologic investigations showed limited variations compared with the SO-191 expedition, mainly in the distribution of fauna. The variety of amphipods seems to be a unique feature of the NZ seeps. The second leg suffered from bad weather conditions, which anticipated work during 100 hrs. out of scheduled 330 hrs. All meta data of the cruise are available through the IFM-GEOMAR Data Management Portal (https://portal.ifm-geomar.de/web/guest/home)

Description: This study performed the first assessment of the volcanic gas output from the Central Volcanic Zone (CVZ) of northern Chile. We present the fluxes and compositions of volcanic gases (H2O, CO2, H2, HCl, HF, and HBr) from five of the most actively degassing volcanoes in this region—Láscar, Lastarria, Putana, Ollagüe, and San Pedro—obtained during field campaigns in 2012 and 2013. The inferred gas plume compositions for Láscar and Lastarria (CO2/Stot = 0.9–2.2; Stot/HCl = 1.4–3.4) are similar to those obtained in the Southern Volcanic Zone of Chile, suggesting uniform magmatic gas fingerprint throughout the Chilean arc. Combining these compositions with our own UV spectroscopy measurements of the SO2 output (summing to ~1800 t d−1 for the CVZ), we calculate a cumulative CO2 output of 1743–1988 t d−1 and a total volatiles output of 〉20,200 t d−1.

Description: Due to the unprecedented rate at which our climate is changing, the ultimate consequence for many species is likely to be either extinction or migration to an alternate habitat. Certain species might, however, evolve at a rate that could make them resilient to the effects of a rapidly changing environment. This scenario is most likely to apply to species that have large population sizes and rapid generation times, such that the genetic variation required for adaptive evolution can be readily supplied. Emiliania huxleyi (Lohm.) Hay and Mohler (Prymnesiophyceae) is likely to be such a species, as it is the most conspicuous extant calcareous phytoplankton species in our oceans with growth rates of 1 day−1. Here we report on a validated set of microsatellites, in conjunction with the coccolithophore morphology motif genetic marker, to genotype 93 clonal isolates collected from across the world. Of these, 52 came from a single bloom event in the North Sea collected on the D366 United Kingdom Ocean Acidification cruise in June–July 2011. There were 26 multilocus genotypes (MLGs) encountered only once in the North Sea bloom and 8 MLGs encountered twice or up to six times. Each of these repeated MLGs exhibited Psex values of less than 0.05, indicating each repeated MLG was the product of asexual reproduction and not separate meiotic events. In addition, we show that the two most polymorphic microsatellite loci, EHMS37 and P01E05, are reporting on regions likely undergoing rapid genetic drift during asexual reproduction. Despite the small sample size, there were many more repeated genotypes than previously reported for other bloom-forming phytoplankton species, including a previously genotyped E. huxleyi bloom event. This study challenges the current assumption that sexual reproduction predominates during bloom events. Whilst genetic diversity is high amongst extant populations of E. huxleyi, the root cause for this diversity and ultimate fate of these populations still requires further examination. Nonetheless, we show that certain CMM genotypes are found everywhere, while others appear to have a regional bias.

Description: Als Teil des nationalen Themenfindungsprozesses setzte sich das erste German Future Earth Summit zum Ziel, die deutsche akademische Community zu stärken und in einem interdisziplinären Umfeld innovative Themenschwerpunkte zu diskutieren. Mit 75 Themenvorschlägen zu den "Future Earth" Schwerpunkten "Dynamic Planet", "Global Development" und "Transformation Towards Sustainability" und mehr als 260 Teilnehmern übertraf die Konferenz alle Erwartungen Meinungen und Ideen zu möglichen "Future Earth"-Themenschwerpunkten, der inter- und transdisziplinären Forschung wurden austauscht und gesammelt, und dienen als Grundlage für weitere Aktivitäten des DKN Future Earth. Der Bericht fasst die Ergebnisse der Konferenz zusammen, die als Basis für die weiteren Diskussionen dienen.

Description: Volatile halogenated organic compounds containing bromine and iodine, which are naturally produced in the ocean, are involved in ozone depletion in both the troposphere and stratosphere. Three prominent compounds transporting large amounts of marine halogens into the atmosphere are bromoform (CHBr3), dibromomethane (CH2Br2) and methyl iodide (CH3I). The input of marine halogens to the stratosphere is based on observations and modeling studies using low resolution oceanic emission scenarios derived from top down approaches. In order to improve emission inventory estimates, we calculate data-based high resolution global sea-to-air flux estimates of these compounds from surface observations within the HalOcAt database (https://halocat.geomar.de/). Global maps of marine and atmospheric surface concentrations are derived from the data which are divided into coastal, shelf and open ocean regions. Considering physical and biogeochemical characteristics of ocean and atmosphere, the open ocean water and atmosphere data are classified into 21 regions. The available data are interpolated onto a 1° × 1° grid while missing grid values are interpolated with latitudinal and longitudinal dependent regression techniques reflecting the compounds' distributions. With the generated surface concentration climatologies for the ocean and atmosphere, global concentration gradients and sea-to-air fluxes are calculated. Based on these calculations we estimate a total global flux of 1.5/2.5 Gmol Br yr−1 for CHBr3, 0.78/0.98 Gmol Br yr−1 for CH2Br2 and 1.24/1.45 Gmol I yr−1 for CH3I (Robust Fit/Ordinary Least Square regression technique). Contrary to recent studies, negative fluxes occur in each sea-to-air flux climatology, mainly in the Arctic and Antarctic region. "Hot spots" for global polybromomethane emissions are located in the equatorial region, whereas methyl iodide emissions are enhanced in the subtropical gyre regions. Inter-annual and seasonal variation is contained within our calculations for all three compounds. Compared to earlier studies, our global fluxes are at the lower end of estimates, especially for bromoform. An underrepresentation of coastal emissions and of extreme events in our estimate might explain the mismatch between our bottom up emission estimate and top down approaches

Description: The Maule earthquake (2010 February 27, Mw 8.8, Chile) broke the subduction megathrust along a previously locked segment. Based on an international aftershock deployment, catalogues of precisely located aftershocks have become available. Using 23 well-located aftershocks, we calibrate the classic teleseismic backprojection procedure to map the high-frequency seismic radiation emitted during the earthquake. The calibration corrects traveltimes in a standard earth model both with a static term specific to each station, and a ‘dynamic’ term specific to each combination of grid point and station. The second term has been interpolated over the whole slipping area by kriging, and is about an order of magnitude smaller than the static term. This procedure ensures that the teleseismic images of rupture development are properly located with respect to aftershocks recorded with local networks and does not depend on accurate hypocentre location of the main shock. We track a bilateral rupture propagation lasting ∼160 s, with its dominant branch rupturing northeastwards at about 3 km s−1. The area of maximum energy emission is offset from the maximum coseismic slip but matches the zone where most plate interface aftershocks occur. Along dip, energy is preferentially released from two disconnected interface belts, and a distinct jump from the shallower belt to the deeper one is visible after about 20 s from the onset. However, both belts keep on being active until the end of the rupture. These belts approximately match the position of the interface aftershocks, which are split into two clusters of events at different depths, thus suggesting the existence of a repeated transition from stick-slip to creeping frictional regime.

Description: An array of broadband seismometers transecting the Talamanca Range in southern Costa Rica was operated from 2005 until 2007. In combination with data from a short‐period network near Quepos in central Costa Rica, this data is analyzed by the receiver function method to image the crustal structure in south‐central Costa Rica. Two strong positive signals are seen in the migrated images, interpreted as the Moho (at around 35 km depth) and an intra‐crustal discontinuity (15 km depth). A relatively flat crustal and Moho interface underneath the north‐east flank of the Talamanca Range can be followed for a lateral distance of about 50 km parallel to the trench, with only slight changes in the overall geometry. Closer to the coast, the topography of the discontinuities shows several features, most notably a deeper Moho underneath the Talamanca Mountain Range and volcanic arc. Under the highest part of the mountain ranges, the Moho reaches a depth of about 50 km, which indicates that the mountain ranges are approximately isostatically compensated. Local deviations from the crustal thickness expected for isostatic equilibrium occur under the active volcanic arc and in south Costa Rica. In the transition region between the active volcanic arc and the Talamanca Range, both the Moho and intracrustal discontinuity appear distorted, possibly related to the southern edge of the active volcanic zone and deformation within the southern part of the Central Costa Rica Deformed Belt. Near the volcanoes Irazu and Turrialba, a shallow converter occurs, correlating with a low‐velocity, low‐density body seen in tomography and gravimetry. Applying a grid search for the crustal interface depth and vp/vs ratio cannot constrain vp/vs values well, but points to generally low values (〈1.7) in the upper crust. This is consistent with quartz‐rich rocks forming the mountain range.

Description: A one‐dimensional reaction‐transport model is used to investigate the dynamics of methane gas in coastal sediments in response to intra‐annual variations in temperature and pressure. The model is applied to data from two shallow water sites in Eckernförde Bay (Germany) characterized by low and high rates of upward fluid advection. At both sites, organic matter is buried below the sulfate‐reducing zone to the methanogenic zone at sufficiently high rates to allow supersaturation of the pore water with dissolved methane and to form a free methane gas phase. The methane solubility concentration varies by similar magnitudes at both study sites in response to bottom water temperature changes and leads to pronounced peaks in the gas volume fraction in autumn when the methanic zone temperature is at a maximum. Yearly hydrostatic pressure variations have comparatively negligible effects on methane solubility. Field data suggest that no free gas escapes to the water column at any time of the year. Although the existence of gas migration cannot be substantiated by direct observation, a speculative mechanism for slow moving gas is proposed here. The model results reveal that free gas migrating upward into the undersaturated pore water will completely dissolve and subsequently be consumed above the free gas depth (FGD) by anaerobic oxidation of methane (AOM). This microbially mediated process maintains methane undersaturation above the FGD. Although the complexities introduced by seasonal changes in temperature lead to different seasonal trends for the depth‐integrated AOM rates and the FGD, both sites adhere to previously developed prognostic indicators for methane fluxes based on the FGD.

Description: During the DRIVE (Diurnal and Regional Variability of Halogen Emissions) ship campaign we investigated the variability of the halogenated very short-lived substances (VSLS) bromoform (CHBr3), dibromomethane (CH2Br2) and methyl iodide (CH3I) in the marine atmospheric boundary layer in the eastern tropical and subtropical North Atlantic Ocean during May/June 2010. The highest VSLS mixing ratios were found near the Mauritanian coast and close to Lisbon (Portugal). With backward trajectories we identified predominantly air masses from the open North Atlantic with some coastal influence in the Mauritanian upwelling area, due to the prevailing NW winds. The maximum VSLS mixing ratios above the Mauritanian upwelling were 8.92 ppt for bromoform, 3.14 ppt for dibromomethane and 3.29 ppt for methyl iodide, with an observed maximum range of the daily mean up to 50% for bromoform, 26% for dibromomethane and 56% for methyl iodide. The influence of various meteorological parameters - such as wind, surface air pressure, surface air and surface water temperature, humidity and marine atmospheric boundary layer (MABL) height - on VSLS concentrations and fluxes was investigated. The strongest relationship was found between the MABL height and bromoform, dibromomethane and methyl iodide abundances. Lowest MABL heights above the Mauritanian upwelling area coincide with highest VSLS mixing ratios and vice versa above the open ocean. Significant high anti-correlations confirm this relationship for the whole cruise. We conclude that especially above oceanic upwelling systems, in addition to sea-air fluxes, MABL height variations can influence atmospheric VSLS mixing ratios, occasionally leading to elevated atmospheric abundances. This may add to the postulated missing VSLS sources in the Mauritanian upwelling region (Quack et al., 2007).

Description: This special section of Atmospheric Chemistry and Physics gives an overview of scientific results, collected during a West Pacific ship expedition in October 2009 with the Research Vessel (R/V) Sonne. The cruise focussed on chemical interactions between the ocean surface and the atmosphere above the tropical West Pacific and was planned within the national research project TransBrom (www.geomar.de/~transbrom). TransBrom aimed to particularly investigate very short lived bromine compounds in the ocean and their transport to and relevance for the stratosphere. For this purpose, chemical and biological parameters were analysed in the ocean and in the atmosphere, accompanied by a high frequency of meteorological measurements, to derive new insights into the multidisciplinary research field. This introduction paper presents the scientific goals and the meteorological and oceanographic background. The main research findings of the TransBrom Sonne expedition are highlighted.

Description: Originating from East Asia, the perennial red macroalga Gracilaria vermiculophylla (Ohmi) Papenfuss has successfully invaded several temperate areas of the Northern hemisphere and continues to spread. In its new range, the seaweed tends to form local mass appearances and to dominate the native community. A high tolerance towards both abiotic and biotic environmental stressors could explain the invasion success of this species. I therefore compared the stress resistance of G. vermiculophylla from six native populations from South Korea and China and eight invasive populations from Europe and NW-Mexico. In short-term experiments G. vermiculophylla individuals were exposed to 1) heat shock, 2) UV-C-radiation and 3) elevated copper concentrations in the water. In a long-term experiment the seaweed had to cope with depletion stress (darkness in combination with low temperature and dryness) for several months. All experiments were carried out twice - one time in the native range in Qingdao, China and one time in the invaded range in Kiel, Germany - to rule out local acclimation effects. In order to compare the resistance against herbivory individuals of native and invasive G. vermiculophylla populations were fed to snails from the native (Littorina brevicula) and the invasive (Littorina littorea) range. In the Baltic Sea, G. vermiculophylla might threaten the habitat-forming native brown alga Fucus vesiculosus through direct competition for resources and by providing a shelter for mesograzers, which prefer to feed on F. vesiculosus. Mesocosm-experiments were conducted over one year in the Kiel Fjord in order to test the direct and indirect effects of G. vermiculophylla on F. vesiculosus.

Description: Processes of the exchange of energy and momentum at the sea-ice/ocean/atmosphere interface are key processes for the polar climate system. The experiment IKAPOS (Investigation of Katabatic winds and Polynyas during Summer) was performed in June 2010. The investigations comprised studies of the summertime katabatic wind system in the coastal area of north and northwest Greenland, and of atmosphere/sea-ice/ocean exchange processes over the North Water Polynya (NOW). The main tool of the experimental study was the polar aircraft POLAR 5 of the Alfred Wegener Institute (AWI), which was based at Qaanaaq (Northwest Greenland). The aircraft was instrumented with turbulence sensors, basic meteorological equipment, radiation and surface temperature sensors, laser altimeters, and video and digital cameras. A total of six research flights have been performed, two of them were katabatic wind flights (over the Humboldt and Steenstrup glacier, respectively). Katabatic wind flights capture conditions of weak and strong synoptically forced katabatic wind. During the NOW flights a fully turbulent stable boundary layer with strong winds of 15 to 20 m s-1 was measured, and channeling effects caused by Smith Sound and Nares Strait were documented. The data of IKAPOS are valuable for the validation of numerical models (including climate models) and will contribute to the understanding of the exchange processes over summertime Arctic polynyas and the Greenland ice sheet.

Description: A latitudinal cross-section and vertical profiles of iodine monoxide (IO) are reported from the marine boundary layer of the Western Pacific. The measurements were taken using Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) during the TransBrom cruise of the German research vessel Sonne, which led from Tomakomai, Japan (42° N, 141° E) through the Western Pacific to Townsville, Australia (19° S, 146° E) in October 2009. In the marine boundary layer within the tropics (between 20° N and 5° S), IO mixing ratios ranged between 1 and 2.2 ppt, whereas in the subtropics and at mid-latitudes typical IO mixing ratios were around 1 ppt in the daytime. The profile retrieval reveals that the bulk of the IO was located in the lower part of the marine boundary layer. Photochemical simulations indicate that the organic iodine precursors observed during the cruise (CH3I, CH2I2, CH2ClI, CH2BrI) are not sufficient to explain the measured IO mixing ratios. Reasonable agreement between measured and modelled IO can only be achieved, if an additional sea-air flux of inorganic iodine (e.g. I2) is assumed in the model. Our observations add further evidence to previous studies that reactive iodine is an important oxidant in the marine boundary layer.

Description: ENDBERICHT (28.06.2013) Gefördert durch das Landesamt für Landwirtschaft, Umwelt und ländliche Räume (LLUR) Schleswig-Holstein, Flintbek, aus der Fischereiabgabe Schleswig-Holstein Förderzeitraum 01.10.2012 – 15.03.2013

Description: At continental margins, the water content and its distribution play an important role in the subduction process. Water is released from the subducting slab in a series of metamorphic reactions and may trigger the onset of melting, cause crustal weakening and changes in the dynamics and thermal structure of subduction zones. However, the amount of water carried into the subduction zone and its distribution are not well constrained by existing data. They are subject of vigorous current research in the special research initiative (SFB 574) at University of Kiel and IFM-GEOMAR “Volatiles and Fluids in Subduction Zones: Climate Feedback and Trigger Mechanisms for Natural Disasters”. Electromagnetic methods like magnetotellurics have been widely used to recognize fluid release and melt production through enhanced electrical conductivities. In the framework of SFB 574, an offshore magnetotelluric experiment was performed in 2007-2008 along a profile crossing the trench, where the Cocos plate is thrust beneath the Caribbean plate. The marine profile was extended onshore by the Free University of Berlin, yielding a large-scale amphibious data set across the subduction zone with a profile length of 370 km. The main goal of the experiment is to image the fluid content and its distribution along the subducting plate and deeper Earth structure. The recorded electromagnetic time series have been processed to electromagnetic sounding curves (apparent resistivity & phase, and Tipper) at each station. As most of the stations lay on a cliffy continental shelf, they were highly susceptible to water enforced movement (tidal currents hitting the shelf). The data quality of the recorded electromagnetic time series therefore ranges from very good to noisy, depending on the instrument’s position and stability. Only quiet sections are used for the processing. In the subsequently derived marine transfer functions a distortion due to the so-called “coast effect” is visible at specific period and distance to the coast (apexes in apparent resistivity curves occur in the transvers-electric (TE) mode, accompanied by phases wandering through all four quadrants and abnormally high Tipper values). A detailed modeling study is performed in order to explain and quantify the coastal distortion. The modeling study reveals that the presence of a coast affects the marine transfer functions with a specific signature, which depends on several physical parameters, such as distance from the coast, period, ocean depth and bulk resistivity. Approximations are derived that define a “characteristic period” and “characteristic distance” from the coast at which the distortion is expected to be most pronounced in the transfer functions. The distortion due to the coast is shown to be helpful as it allows the estimation of the bulk resistivity of the subsurface and furthermore increases the sensitivity of the electromagnetic response to conductivity anomalies at depth. The recorded marine transfer functions were inverted together with the land transfer functions to an electrical resistivity model of the subduction zone down to a depth of approximately 120 km. Based on the model the hydration and dehydration cycle of a subduction zone may be derived. An electrically conductive zone in the incoming plate outer rise is associated with sea water penetrating down extensional faults and cracks into the upper mantle. Along the downward subducting plate, distinct conductive anomalies identify fluids from dehydration processes in the sediments, crust and mantle. A conductivity anomaly at a depth of approximately 12 km and at a distance of 65 km from the trench is associated with a first major dehydration reaction of minerally-bound water. This is of importance in the context of mid-slope fluid seeps which are thought to significantly contribute to the recycling of minerally-bound water. Another fluid accumulation is revealed by a conductivity anomaly at 20-30 km depth and a distance of approximately 30 km seaward from the volcanic arc. This lower crustal fluid accumulation could likely be caused by trapping of fluids released due to de-serpentinization processes or due to other mineral dehydration processes. A comparison with other electromagnetic studies from subduction zones around the world reveal that such a conductivity anomaly is a global feature suggesting the presence of a global fluid sink. This sink may help to explain the general observed deficit between water input and output in a subduction cycle. By relating seismic evidence as well as petrological results collected in the multi-disciplinary study of Costa Rica, budget estimations for the water cycle in the subduction zone are introduced.

Description: The Atlantic meridional overturning circulation (AMOC) carries large amounts of heat into the North Atlantic influencing climate regionally as well as globally. Palaeo-records and simulations with comprehensive climate models suggest that the positive salt-advection feedback may yield a threshold behaviour of the system. That is to say that beyond a certain amount of freshwater flux into the North Atlantic, no meridional overturning circulation can be sustained. Concepts of monitoring the AMOC and identifying its vicinity to the threshold rely on the fact that the volume flux defining the AMOC will be reduced when approaching the threshold. Here we advance conceptual models that have been used in a paradigmatic way to understand the AMOC, by introducing a density-dependent parameterization for the Southern Ocean eddies. This additional degree of freedom uncovers a mechanism by which the AMOC can increase with additional freshwater flux into the North Atlantic, before it reaches the threshold and collapses: an AMOC that is mainly wind-driven will have a constant upwelling as long as the Southern Ocean winds do not change significantly. The downward transport of tracers occurs either in the northern sinking regions or through Southern Ocean eddies. If freshwater is transported, either atmospherically or via horizontal gyres, from the low to high latitudes, this would reduce the eddy transport and by continuity increase the northern sinking which defines the AMOC until a threshold is reached at which the AMOC cannot be sustained. If dominant in the real ocean this mechanism would have significant consequences for monitoring the AMOC.

Description: Production pathways of the prominent volatile organic halogen compound methyl iodide (CH3I) are not fully understood. Based on observations, production of CH3I via photochemical degradation of organic material or via phytoplankton production has been proposed. Additional insights could not be gained from correlations between observed biological and environmental variables or from biogeochemical modeling to identify unambiguously the source of methyl iodide. In this study, we aim to address this question of source mechanisms with a three-dimensional global ocean general circulation model including biogeochemistry (MPIOM-HAMOCC (MPIOM - Max Planck Institute Ocean Model HAMOCC - HAMburg Ocean Carbon Cycle model)) by carrying out a series of sensitivity experiments. The simulated fields are compared with a newly available global data set. Simulated distribution patterns and emissions of CH3I differ largely for the two different production pathways. The evaluation of our model results with observations shows that, on the global scale, observed surface concentrations of CH3I can be best explained by the photochemical production pathway. Our results further emphasize that correlations between CH3I and abiotic or biotic factors do not necessarily provide meaningful insights concerning the source of origin. Overall, we find a net global annual CH3I air-sea flux that ranges between 70 and 260 Gg yr(-1). On the global scale, the ocean acts as a net source of methyl iodide for the atmosphere, though in some regions in boreal winter, fluxes are of the opposite direction (from the atmosphere to the ocean).

Description: Subduction of the oceanic Cocos plate offshore Costa Rica causes strong advection of methane-charged fluids. Presented here are the first direct measurements of microbial anaerobic oxidation of methane (AOM) and sulfate reduction (SR) rates in sediments from the two mounds, applying radiotracer techniques in combination with numerical modeling. In addition, analysis of carbonate δ18O, δ13C, and 87Sr / 86Sr signatures constrain the origin of the carbonate-precipitating fluid. Average rates of microbial activities showed differences with a factor of 4.8 to 6.3 between Mound 11 [AOM 140.71 (±40.84 SD); SR 117.25 (±82.06 SD) mmol m−2 d−1, respectively] and Mound 12 [AOM 22.37 (±0.85 SD); SR 23.99 (±5.79 SD) mmol m−2 d−1, respectively]. Modeling results yielded flow velocities of 50 cm a−1 at Mound 11 and 8–15 cm a−1 at Mound 12. Analysis of oxygen and carbon isotope variations of authigenic carbonates from the two locations revealed higher values for Mound 11 (δ18O: 4.7 to 5.9‰, δ13C: −21.0 to −29.6‰), compared to Mound 12 (δ18O: 4.1 to 4.5‰, δ13C: −45.7 to −48.9‰). Analysis of carbonates 87Sr / 86Sr indicated temporal changes of deep-source fluid admixture at Mound 12. The present study is in accordance with previous work supporting considerable differences of methane flux between the two Mounds. It also strengthens the hypothesis of a predominantly deep fluid source for Mound 11 versus a rather shallow source of biogenic methane for Mound 12. The results demonstrate that methane-driven microbial activity is a valid ground truthing tool for geophysical measurements of fluid advection and constraining of recent methane fluxes in the study area. The study further shows that the combination of microbial rate measurements, numerical modeling, and authigenic carbonate analysis provide a suitable approach to constrain temporal and spatial variations of methane charged fluid flow at the Pacific Costa Rican margin.

Description: A direct monitoring of European silver eel (Anguilla anguilla, L) escapement from rivers and estuaries has been proven to be challenging, and a Europe-wide documentation of escaping silver eel numbers therefore hardly seems realistic. To reinforce management decisions, policy-makers are thus widely reliant on the accuracy of escapement models. A 3-year programme of silver eel escapement monitoring was undertaken to compile model input data and revise an eel population model (German Eel Model II; GEM II) already used in the decision-making process of management authorities. By compiling necessary input data and analysing vital system-specific population characteristics, it was possible to compare the documented silver eel escapement with the modelled potential silver eel escapement. Resulting model predictions were close to actually monitored escapement numbers, which were distinctly lower than reference escapement values for the same freshwater system given in the implementation report of the German Eel Management Plans. Applying different commercial and recreational catch scenarios revealed the sensitivity of the model. The results show the potential of the GEM II and highlight the importance of high-quality input data to use model predictions as the basis for management measures.

Description: We carry out a case study of the transport and chemistry of bromoform and its product gases (PGs) in a sea breeze driven convective episode on 19 November 2011 along the North West coast of Borneo during the "Stratospheric ozone: Halogen Impacts in a Varying Atmosphere" (SHIVA) campaign. We use ground based, ship, aircraft and balloon sonde observations made during the campaign, and a 3-D regional online transport and chemistry model capable of resolving clouds and convection explicitly that includes detailed bromine chemistry. The model simulates the temperature, wind speed, wind direction fairly well for the most part, and adequately captures the convection location, timing, and intensity. The simulated transport of bromoform from the boundary layer up to 12 km compares well to aircraft observations to support our conclusions. The model makes several predictions regarding bromine transport from the boundary layer to the level of convective detrainment (11 to 12 km). First, the majority of bromine undergoes this transport as bromoform. Second, insoluble organic bromine carbonyl species are transported to between 11 and 12 km, but only form a small proportion of the transported bromine. Third, soluble bromine species, which include bromine organic peroxides, hydrobromic acid (HBr), and hypobromous acid (HOBr), are washed out efficiently within the core of the convective column. Fourth, insoluble inorganic bromine species (principally Br2) are not washed out of the convective column, but are also not transported to the altitude of detrainment in large quantities. We expect that Br2 will make a larger relative contribution to the total vertical transport of bromine atoms in scenarios with higher CHBr3 mixing ratios in the boundary layer, which have been observed in other regions. Finally, given the highly detailed description of the chemistry, transport and washout of bromine compounds within our simulations, we make a series of recommendations about the physical and chemical processes that should be represented in 3-D chemical transport models (CTMs) and chemistry climate models (CCMs), which are the primary theoretical means of estimating the contribution made by CHBr3 and other very short-lived substances (VSLS) to the stratospheric bromine budget.

Description: Grazing by the isopod Idotea baltica induces chemical defenses in the brown seaweed Fucus vesiculosus. A combination of a 33 day induction experiment, feeding choice assays and functional genomic analyses was used to investigate temporal defense patterns and to correlate changes in palatability to changes in gene expression. Despite permanent grazing, seaweed palatability varied over time. Controls were significantly more consumed than grazed pieces only after 18 and 27 days of grazing. Relative to controls, 562/402 genes were up-/down-regulated in seaweed pieces that were grazed for 18 days, i.e. when defense induction was detected. Reprogramming of the regulative expression orchestra (translation, transcription), up-regulation of genes involved in lipid and carbohydrate metabolism, intracellular trafficking, defense and stress response, as well as downregulation of photosynthesis was found in grazed seaweed. These findings indicate short-term temporal variation in defenses and that modified gene expression patterns arise at the same time when grazed seaweed pieces show reduced palatability. Several genes with putative defensive functions and cellular processes potentially involved in defence, such as reallocation of resources from primary to secondary metabolism, were revealed

Description: The stratospheric climate and variability from simulations of sixteen chemistryclimate models is evaluated. On average the polar night jet is well reproduced though its variability is less well reproduced with a large spread between models. Polar temperature biases are less than 5 K except in the Southern Hemisphere (SH) lower stratosphere in spring. The accumulated area of low temperatures responsible for polar stratospheric cloud formation is accurately reproduced for the Antarctic but underestimated for the Arctic. The shape and position of the polar vortex is well simulated, as is the tropical upwelling in the lower stratosphere. There is a wide model spread in the frequency of major sudden stratospheric warnings (SSWs), late biases in the breakup of the SH vortex, and a weak annual cycle in the zonal wind in the tropical upper stratosphere. Quantitatively, “metrics” indicate a wide spread in model performance for most diagnostics with systematic biases in many, and poorer performance in the SH than in the Northern Hemisphere (NH). Correlations were found in the SH between errors in the final warming, polar temperatures, the leading mode of variability, and jet strength, and in the NH between errors in polar temperatures, frequency of major SSWs, and jet strength. Models with a stronger QBO have stronger tropical upwelling and a colder NH vortex. Both the qualitative and quantitative analysis indicate a number of common and long‐standing model problems, particularly related to the simulation of the SH and stratospheric variability.

Description: Continuous high-resolution underway measurements of dimethyl sulfide (DMS) and isoprene in the ocean surface were conducted from Germany to South Africa in November 2008. DMS, total dimethylsulfoniopropionate (DMSPt), isoprene and 19'-hexanoyloxyfucoxanthin (19'-hex) correlated in nitrogen-depleted regions when they were clustered by nitrogen to phosphorous ratio (N:P). The 19'-hex-containing algae groups might be a common source of DMS, DMSPt, and isoprene in the low N: P regions. Additionally, DMS and isoprene correlated in nitrate-depleted regions when they were clustered against nitrate concentrations. Correlations between DMS and isoprene were also found within nitrate-depleted eddies encountered along the cruise track. Eddies with N: P of similar to 2.8 showed the highest positive correlations between DMS and isoprene. We conclude that the DMS/isoprene relationships in the eastern Atlantic Ocean were influenced by nutrient availability, with implications for using nutrients to predict the DMS and isoprene concentrations over a range of oceanographic areas depleted in nitrogen

Description: Stratospheric sudden warmings (SSWs) are extreme events in the polar stratosphere that are both caused by and have effects on the tropospheric flow. This means that SSWs are associated with changes in the angular momentum of the atmosphere, both before and after their onset. Because these angular momentum changes are transferred to the solid Earth, they can be observed in the rate of the Earth's rotation and the wobble of its rotational pole. By comparing observed Earth rotation variations to reanalysis data, we find that an anomaly in the orientation of the Earth's rotational pole, up to 4 times as large as the annual polar wobble, typically precedes SSWs by 20-40 days. The polar motion signal is due to pressure anomalies that are typically seen before SSW events and represents a new type of observable that may aid in the prediction of SSWs. A decline in the length of day is also seen, on average, near the time of the SSW wind reversal and is found to be due to anomalous easterly winds generated in the tropical troposphere around this time, though the structure and timing of this signal seems to vary widely from event to event.

Description: We describe the main differences in simulations of stratospheric climate and variability by models within the fifth Coupled Model Intercomparison Project (CMIP5) that have a model top above the stratopause and relatively fine stratospheric vertical resolution (high-top), and those that have a model top below the stratopause (low-top). Although the simulation of mean stratospheric climate by the two model ensembles is similar, the low-top model ensemble has very weak stratospheric variability on daily and interannual time scales. The frequency of major sudden stratospheric warming events is strongly underestimated by the low-top models with less than half the frequency of events observed in the reanalysis data and high-top models. The lack of stratospheric variability in the low-top models affects their stratosphere-troposphere coupling, resulting in short-lived anomalies in the Northern Annular Mode, which do not produce long-lasting tropospheric impacts, as seen in observations. The lack of stratospheric variability, however, does not appear to have any impact on the ability of the low-top models to reproduce past stratospheric temperature trends. We find little improvement in the simulation of decadal variability for the high-top models compared to the low-top, which is likely related to the fact that neither ensemble produces a realistic dynamical response to volcanic eruptions

Description: This cumulative work summarizes seven manuscripts published between 2007 and 2012. These studies use marine and on-shore tephrostratigraphy as a tool to quantify and identify the timing, extent, and causes of geological processes taken place at subductions zones. In many subduction-related regions on Earth, highly explosive plinian volcanic eruptions generate buoyant, tephra bearing eruption columns capable of penetrating up to 40 km into the stratosphere, where they reach a neutral level of buoyancy and spread laterally. Such eruption clouds drift with the prevailing wind over nearby oceans, gradually dropping their ash load over areas that sometimes can be larger than 106 km2. The resulting ash layers are best preserved in non-erosive marine environments and thus provide the most complete record of volcanic activity. Wide aerial distribution across sedimentary facies boundaries, near-instantaneous emplacement, correlative chemical signatures, and the presence of minerals suitable for radiometric dating make ash layers an excellent stratigraphic marker in marine sediments and provide constraints on the temporal evolution of both, the volcanic source region and the ash-containing sediment facies. On-shore stratigraphic successions of tephra layers are generally based on the distinct composition of tephras. In west-central Nicaragua for example (section 2.1), late Pleistocene to Holocene tephras were emplaced by highly explosive eruptions, with a combined erupted mass of 184 Gt (DRE), that are distributed into 9 dacitic to rhyolitic eruptions (84%) and 4 basaltic to basaltic-andesitic eruptions (16%). Widespread eruptive masses from explosive volcanism are usually underestimated, even when the most distal parts of the on-shore distribution fans, normally not preserved in terrestrial environments, are included. If on-shore tephras can be correlated to offshore deposits like those in Central America (sections 2.2 and 2.3), the revised erupted magma mass show that the tephras account for 65% of the total arc magma output. This enables the minimum estimation of long-term average magma production rate at each volcano and over whole arcs. Using their unique compositional signatures, tephras facilitate the determination of provenance as well as the reconstruction of emplacement processes of volcanoclastic marine sediments, in accordance with regional geotectonic settings (section 2.4). Ash layers in marine sediments offshore Central America can provide time constraints for submarine landslides at the continental slope, as they probably act as weak layers where sliding initiates (section 2.5). Variations in the sedimentation rates on the slope, constrained by bracketing tephras of known age, can be attributed to periods of intense erosion on land likely triggered by tectonic processes. In the case of the incoming plate these changes can be due to changes in bend-faulting activity across the outer rise, which elicit erosion and re-sedimentation. Additionally, ash layers in Central America can help determine the duration of active and inactive periods in the multi-stage growth history of fluid venting sites (section 2.6). Cyclicity in the marine tephra record along the Pacific Ring of Fire yields a statistically significant detection of a spectral peak at the obliquity period, which is related to crustal stress changes associated with ice age mass redistribution and therefore supports the presence of a causal link between variations in ice age climate, continental stress field, and volcanism (section 2.7). To summarize, the seven manuscripts presented here highlight the benefit of tephrostratigraphy as a major tool in geology, and show that the tephra record on-shore and, especially in the marine environment, have a spectrum of possible applications to decipher the causes and temporal variability of geological processes.

Description: Recent studies indicate that the tropical ocean is losing oxygen. This becomes crucial in regions adjacent to eastern boundary currents, as the productivity of these systems is already accompanied by oxygen minimum zones (OMZ) at depth below the photic zone. The extent of low oxygen water masses influences dissolved nutrient inventories, as oxygen-sensitive nitrogen (N) loss processes such as denitrification and anammox are enhanced and inorganic phosphorus is remobilized from sediments, resulting in low N:P of upwelled waters, especially in the East Pacific. The present study aimed to investigate the impact of changing N and P supply on the pelagic primary producers and consumers in the photic zone. To achieve this, nutrient manipulation experiments were conducted in the eastern tropical Pacific and Atlantic Ocean using a newly designed shipboard mesocosm setup. Results demonstrated that in these regions, where N:P is generally below the canonical Redfield ratio of 16, inorganic N is the key control of bulk productivity regardless of the amount of P added, especially of bloom-forming diatom species and ciliate consumers (chapter I and II). However, the response of individual species and pools of organic matter was found to be more complex. For example, Phaeocystis globosa and Heterosigma sp. clearly benefitted from high P-levels (chapter I). Both algal groups are considered of inferior quality to mesozooplankton consumers compared to diatom-dominated assemblages. The observation that the relative content of unsaturated fatty acids in the particulate matter was positively related to diatom biomass (chapter I) is a second clue that decreasing N flux to the surface ocean impacts food web productivity. However, the RNA/DNA ratio, as a proxy for nutritional condition, did not change in the copepod Undinula vulgaris when fed on the manipulated mesocosm community over a period of three days (chapter II). The results of the nutrient manipulation experiments off Peru and West Africa were surprisingly similar, despite the fact that the North Atlantic features excess N at depth due to N2-fixation and the lack of suboxic conditions that would promote N-loss processes. Furthermore, pigments characteristic for cyanobacteria indicated that diazotrophs were increasing in those mesocosms that had received a higher initial N load (chapter I and II), which contradicts the common understanding that diazotrophs would benefit from excess P. In addition, we observed that the N:P excretion ratio of copepods (U. vulgaris) feeding on the manipulated mesocosm assemblage was influenced by the N:P of bulk particulate organic matter (PON:POP), which in turn responded directly to the manipulation ratios (chapter II). In order to survey the natural variability in N and P excretion rates in the Eastern Tropical North Atlantic, measurements were conducted in shipboard incubations at several stations on three epipelagic copepod species (chapter III). Within species, excretion N:P was positively related to PON:POP at the respective station; however, the low number of stations sampled and the variability of PON:POP within the upper 150 m hampered the establishment of a functional relationship. The N:P excretion ratio was consistently higher in the carnivorous Euchaeta marina compared to the omnivorous U. vulgaris and Scolecithrix danae. This can be attributed to the rather rigid N:P stoichiometry of zooplanktonic prey items of E. marina in contrast to the unicellular food items of the other two species (such as diatoms, dinoflagellates and heterotrophic protists) with more variable N:P. A further question addressed in this study was to what extent atmospheric N sources (N2-fixation and dust) are contributing to secondary production in the Eastern Tropical North Atlantic, and how this contribution is related to the vertical flux of dissolved inorganic nitrogen (chapter IV). We used zooplankton stable nitrogen isotopes (15N) to estimate the relative contribution of atmospheric N sources and found that it ranged from less than 20% off the West African coast to 60% in the open ocean (Guinea Dome region), and was positively related to the depth of the nitracline.

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: Temporal changes in the water mass distribution and biogeochemical signals in the tropical eastern South Pacific are investigated with the help of an extended optimum multi-parameter (OMP) analysis, a technique for inverse modeling of mixing and biogeochemical processes through a multidimensional least-square fit. Two ship occupations of a meridional section along 85°50' W from 14° S to 1° N are analysed during relatively warm (El Niño/El Viejo, March 1993) and cold (La Niña/La Vieja, February 2009) upper-ocean phases. The largest El Niño–Southern Oscillation (ENSO) impact was found in the water properties and water mass distribution in the upper 200 m north of 10° S. ENSO promotes the vertical motion of the oxygen minimum zone (OMZ) associated with the hypoxic equatorial subsurface water (ESSW). During a cold phase the core of the ESSW is found at shallower layers, replacing shallow (top 200 m) subtropical surface water (STW). The heave of isopycnals due to ENSO partially explains the intrusion of oxygen-rich and nutrient-poor antarctic intermediate water (AAIW) into the depth range of 150–500 m. The other cause of the AAIW increase at shallower depths is that this water mass flowed along shallower isopycnals in 2009. The shift in the vertical location of AAIW reaching the OMZ induces changes in the amount of oxygen advected and respired inside the OMZ: the larger the oxygen supply, the greater the respiration and the lower the nitrate loss through denitrification. Variations in the intensity of the zonal currents in the equatorial current system, which ventilates the OMZ from the west, are used to explain the patchy latitudinal changes of seawater properties observed along the repeated section. Significant changes reach down to 800 m, suggesting that decadal variability (Pacific decadal oscillation) is also a potential driver in the observed variability.

Description: Microbial degradation of substrates to terminal products is commonly understood as a unidirectional process. In individual enzymatic reactions, however, reversibility (reverse reaction and product back flux) is common. Hence, it is possible that entire pathways of microbial degradation are associated with back flux from the accumulating product pool through intracellular intermediates into the substrate pool. We investigated carbon and sulfur back flux during the anaerobic oxidation of methane (AOM) with sulfate, one of the least exergonic microbial catabolic processes known. The involved enzymes must operate not far from the thermodynamic equilibrium. Such an energetic situation is likely to favor product back flux. Indeed, cultures of highly enriched archaeal–bacterial consortia, performing net AOM with unlabeled methane and sulfate, converted label from 14C-bicarbonate and 35S-sulfide to 14C-methane and 35S-sulfate, respectively. Back fluxes reached 5% and 13%, respectively, of the net AOM rate. The existence of catabolic back fluxes in the reverse direction of net reactions has implications for biogeochemical isotope studies. In environments where biochemical processes are close to thermodynamic equilibrium, measured fluxes of labeled substrates to products are not equal to microbial net rates. Detection of a reaction in situ by labeling may not even indicate a net reaction occurring in the direction of label conversion but may reflect the reverse component of a so far unrecognized net reaction. Furthermore, the natural isotopic composition of the substrate and product pool will be determined by both the forward and back flux. This finding may have to be considered in the interpretation of stable isotope records.

Description: We discuss potential transitions of six climatic subsystems with large-scale impact on Europe, sometimes denoted as tipping elements. These are the ice sheets on Greenland and West Antarctica, the Atlantic thermohaline circulation, Arctic sea ice, Alpine glaciers and northern hemisphere stratospheric ozone. Each system is represented by co-authors actively publishing in the corresponding field. For each subsystem we summarize themechanism of a potential transition in a warmer climate along with its impact on Europe and assess the likelihood for such a transition based on published scientific literature. As a summary, the ‘tipping’ potential for each system is provided as a function of global mean temperature increase which required some subjective interpretation of scientific facts by the authors and should be considered as a snapshot of our current understanding.

Description: Species richness is the most commonly used but controversial biodiversity metric in studies on aspects of community stability such as structural composition or productivity. The apparent ambiguity of theoretical and experimental findings may in part be due to experimental shortcomings and/or heterogeneity of scales and methods in earlier studies. This has led to an urgent call for improved and more realistic experiments. In a series of experiments replicated at a global scale we translocated several hundred marine hard bottom communities to new environments simulating a rapid but moderate environmental change. Subsequently, we measured their rate of compositional change (re-structuring) which in the great majority of cases represented a compositional convergence towards local communities. Re-structuring is driven by mortality of community components (original species) and establishment of new species in the changed environmental context. The rate of this re-structuring was then related to various system properties. We show that availability of free substratum relates negatively while taxon richness relates positively to structural persistence (i.e., no or slow re-structuring). Thus, when faced with environmental change, taxon-rich communities retain their original composition longer than taxon-poor communities. The effect of taxon richness, however, interacts with another aspect of diversity, functional richness. Indeed, taxon richness relates positively to persistence in functionally depauperate communities, but not in functionally diverse communities. The interaction between taxonomic and functional diversity with regard to the behaviour of communities exposed to environmental stress may help understand some of the seemingly contrasting findings of past research.