Active mud volcanoes on the upper slope of the western Nile deep-sea fan—first results from the P362/2 cruise of R/V Poseidon

In February 2008, cruise P362/2 was undertaken aboard R/V Poseidon to the Giza and North Alex mud volcanoes (MVs) on the upper slope of the western Nile deep-sea fan. Emitted fluids were strongly depleted in chloride and rich in hydrocarbons, predominantly of thermogenic origin. In-situ sediment temperature measurements indicate extremely high and moderate levels of activity for the North Alex MV and Giza MV, respectively, and suggest rapid changes from dormant to active stages. Both the physical properties of core sediments (e.g., color and magnetic susceptibility), and their assemblages of micro- and nannofossils point to different sources for the two mud volcanoes. Biostratigraphic dating suggests source depths of 2,100–2,450 mbsf for the Giza MV and 1,150–1,550 mbsf for the North Alex MV. Very high temperatures of up to 70°C in shallow sediments at the North Alex MV can be explained only if the fluid source were warmer and deeper than the sediment source.     

Climate and climate change in western canada as simulated by the Canadian regional climate model

Abstract

A þrst climate simulation performed with the novel Canadian Regional Climate Model (CRCM) is presented. The CRCM is based on fully elastic non‐hydrostatic þeld equations, which are solved with an efþcient semi‐implicit semi‐Lagrangian (SISL) marching algorithm, and on the parametrization package of subgrid‐scale physical effects of the second‐generation Canadian Global Climate Model (GCMII). Two 5‐year integrations of the CRCM nested with GCMII simulated data as lateral boundary conditions are made for conditions corresponding to current and doubled CO₂ scenarios. For these simulations the CRCM used a grid size of 45 km on a polar‐stereographic projection, 20 scaled‐height levels and a time step of 15 min; the nesting GCMII has a spectral truncation of T32, 10 hybrid‐pressure levels and a time step of 20 min. These simulations serve to document: (1) the suitability of the SISL numerical scheme for regional climate modelling, (2) the use of GCMII physics at much higher resolution than in the nesting model, (3) the ability of the CRCM to add realistic regional‐scale climate information to global model simulations, and (4) the climate of the CRCM compared to that of GCMII under two greenhouse gases (GHG) scenarios.     

Spartina anglica eradication experiment and in situ monitoring assess structuring strength of habitat complexity on marine macrofauna at high tidal level

The cordgrass Spartina anglica is an introduced species that tends to invade sheltered sand and mudflats, at the upper low marsh level. In Arcachon Bay, a lagoon in South West of France, the cordgrass can also replace Zostera noltii beds. The consequence of cordgrass presence on macrobenthic fauna was estimated and compared to adjacent habitats (bare sands, Z. noltii sea grass beds) during one year. The communities of the three habitats were characterised by low species richness, low abundance and biomass (when Hydrobia ulvae, 90% of abundance, is not considered) and high seasonal stability. The infaunal assemblages were particularly homogeneous between habitats without any characteristic species.Cordgrass eradication experiments were performed and zoobenthic recolonisation was observed the following year. Modifications in benthic fauna were observed on epifauna only.These results highlight the limited structuring effect of habitat heterogeneity at high tidal levels and in soft-bottom sediments where desiccation becomes the dominant factor determining infauna community structure.     

LINET—An international lightning detection network in Europe

During the past years a VLF/LF lightning detection network (LINET) was developed at the University of Munich, which provides continuous data for both research and operational purposes. In particular, the network introduces five new features: a) total lightning capability: both cloud-to-ground strokes (CG) and cloud lightning (IC) are measured; b) low-amplitude reporting: weak lightning events from discharge channel with currents well below 5 kA are detected within the central part of the network, whereby IC events dominate; c) new 3D-discrimination: a time-of-arrival method is utilized to separate CG from IC with good reliability, provided that the sensor baseline does not exceed ~ 250 km; d) IC emission height: for each cloud event a height is determined which is thought to reflect the central region of the involved channel; and e) optimised location accuracy: due to precision and combined action of all influential network components, complemented by site-error corrections, the position accuracy of strokes reaches an average value as small as ~ 150 m, whereby false locations (‘outliers’) rarely occur. During international co-operations LINET has been deployed in four continents: Europe (initially Germany), South America (area of Bauru, Brazil), Australia (around Darwin), and Central Africa (Benin). Since the features quoted above could be verified in the tests, a 65-sensor network was established in Europe and started on May 1, 2006, in co-operation with the service company nowcast. LINET covers a wide area approximately from longitude − 10° to 25° to latitude 35° to 66°; it is available for scientific projects and officially utilized by the German Weather Service for operational purposes. Meanwhile, the network was extended by deployment of additional sites so that it comprises about 90 sensors in 17 countries.     

Experiments and geochemical modelling of CO2 sequestration by olivine: Potential,quantification

Aqueous solutions equilibrated with supercritical CO₂ (150 °C and total pressure of 150 bar) were investigated in order to characterize their respective conditions of carbonation. Dissolution of olivine and subsequent precipitation of magnesite with a net consumption of CO₂ were expected. A quantified pure mineral phase (powders with different olivine grain diameter [20–80 μm], [80–125 μm], [125–200 μm] and [>200 μm]), and CO₂ (as dried ice) were placed in closed-batch reactors (soft Au tubes) in the presence of solutions. Different salinities (from 0 to 3400 mM) and different ratios of solution/solid (mineral phase) (from 0.1 to 10) were investigated. Experiments were performed over periods from 2 to 8 weeks. Final solid products were quantified by the Rock-Eval 6 technique, and identified using X-ray diffraction, Raman spectroscopy, electron microprobe and scanning electron microscopy. Gaseous compounds were quantified by a vacuum line equipped with a Toepler pump and identified and measured by gas chromatography (GC). Carbon mass balances were calculated.     

Le volcanisme triasique des din arides en yougoslavie: SA place dans l'evolution geotectonique peri-mediterraneenne

The Aniso-Ladinian “porphyrite—radiolarite” formation which outcrops in all the paleogeographical zones of the Dinarides includes, on the one hand, a series of carbonate-pelite sediments with sandstones and radiolarian cherts, and on the other, pyroclastic formations and lava flows. It is contemporaneous with the formation of troughs and ridges. The magmatic rocks consist of (1) basalts and spilites (2) andesites and andesitic tuffs (3) dolerites, diabases and gabbros (4) quartz-rich rhyolites and tuffs.Preliminary geochemical studies reveal that the andsites and basalts are rich in alumina, poor in titanium and show a calc-alkaline trend.The Yugoslavian middle Triassic magmatism is very different from that related to continental rifting, but is not unlike present-day calc-alkaline series in volvanic arcs. This leads one to suppose that the individualisation of throughs and ridges in the Dinarides during Triassic times is related to convergent plate movements, as is at present the opening of inter-arc basins. This raises the controversial question of the existence of a Paleotethys during the Hercynian.     

Structure-from-motion,multi-view stereo photogrammetry applied to line-scan sediment core images

Journal of Paleolimnology - Images of sediment cores are often acquired to preserve primary color information, before such profiles are altered by subsequent sampling and destructive analyses. In...     

Benthic indicators and index approaches in the three main estuaries along the French Atlantic coast (Seine, Loire and Gironde)

The three main estuaries in the French Atlantic coast – the Seine, Loire and Gironde, all with high tidal regimes – are interfaces between the continental and the coastal ecosystems. The Seine and Gironde are highly contaminated, whereas the Loire remains in a more natural state. Both the Seine and Gironde have suffered from harbour construction, and as a result, their biological units are extremely compartmentalized. Benthic species and communities have adapted to tolerate temporal physical and chemical changes ( e.g. salinity, substrata, depth, and levels of fine particles and oxygen) and human activities ( e.g. dredging, shipping traffic, and habitat reduction). Although numerous bio-indicators and indices are used to define the ecological quality status (EcoQS) of coastal waters, very few of them were developed specifically for environments with a mosaic of conditions and salinity levels, including freshwater. The main problem appears to be that all the indices for determining anthropogenic stress examine the abundances of stress-tolerant species, which may also be able to tolerate natural stressors such as those occurring in estuaries. This paper takes a look at the development status of the benthic indicators and index approaches used in the three main estuaries along the French Atlantic coast. In addition, it examines the adaptation of the different benthic indicators to the taxonomic sufficiency principle, and the adaptation of the Benthic Opportunistic Polychaetes Amphipods index (BOPA) and the Benthic Opportunistic Annelida Amphipod index (BO2A) for use in the freshwater zones of transitional waters ( i.e. up to the upper limit of the tidal range). Several perspectives are discussed in light of the diverse disturbances and the heterogeneity of such stressed zones, such as the use of multimetric and scoring approaches.     

Estimation of optical properties of arctic haze using a numerical model

Abstract

The optical parameters of Arctic haze, such as the scattering and the absorption coefficients and the asymmetry factor, have been estimated using a theoretical haze model. The Aden and Kerker solution for spherical nuclei coated with a spherical shell was employed to account for the observed sulphuric acid coating on Arctic aerosols. Six original aerosol materials are considered; four are natural and two are anthropogenic in origin (sulphuric acid and soot). The relative humidity is varied between 0 and 99% and the effects of anthropogenic substances are examined. Carbonaceous material can increase the absorption coefficient by up to a factor 5 in the visible range, while sulphuric acid significantly increases the growth of particles and affects all of the optical parameters. The haze model is found to be consistent with available measurements of aerosol characteristics and optical parameters. The haze model is then used to convert a vertical profile of the extinction coefficient to a profile of particle concentration.