Impact of the Eastern Mediterranean Transient on the distribution of anthropogenic CO₂ and first estimate of acidification for the Mediterranean Sea     

Franck Touratier  Catherine Goyet 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(1):1-15

In the Mediterranean Sea the carbon chemistry is poorly known. However, the impact of the regional and large-scale anthropogenic pressures on this fragile environment rapidly modifies the distribution of the carbonate system key properties like C_T (total dissolved inorganic carbon), A_T (total alkalinity), C_ANT (anthropogenic CO₂), and pH. This leads inexorably to the acidification of its waters. In order to improve our knowledge, we first develop interpolation procedures to estimate C_T and A_T from oxygen, salinity, and temperature data using all available data from the EU/MEDAR/MEDATLAS II database. The acceptable levels of precision obtained for these estimates (6.11 ??mol-kg⁻¹ for C_T and 6.08 ??mol kg⁻¹ for A_T) allow us to draw the distribution of C_ANT (with an uncertainty of 6.75 ??mol kg⁻¹) using the Tracer combining Oxygen, inorganic Carbon, and total Alkalinity (TrOCA) approach. The results indicate that: 1) all Mediterranean water bodies are contaminated by anthropogenic carbon; 2) the lowest concentration of C_ANT is 37.5 ??mol kg⁻¹; and 3) the western basin is more contaminated than the Eastern basin. After reconstructing the distribution of key properties (C_T, A_T, C_ANT) for four periods of time (between 1986 and 2001) along a west-east section throughout the whole Mediterranean Sea, we analyze the impact of the Eastern Mediterranean Transient (EMT). Not only has the concentration of C_ANT increased (especially in the intermediate and the bottom layers of the eastern basin, during and after the EMT), but also the distribution of all properties has been considerably perturbed. This is discussed in detail. For the first time, the level of acidification is estimated for the Mediterranean Sea. Our results indicate that for the year 2001 all waters (even the deepest) have been acidified by values ranging from −0.14 to −0.05 pH unit since the beginning of the industrial era, which is clearly higher than elsewhere in the open ocean. Given that the pH of seawater may affect a very large number of chemical and biological processes, our results stress the necessity to develop new programs of research to understand and then predict the evolution of the carbonate system properties in the Mediterranean Sea.  相似文献   

An interpretation of the nitrogen deficiency in comets     

Nicolas Iro  Franck Hersant  Jonathan I. Lunine 《Icarus》2003,161(2):511-532

We propose an interpretation of the composition of volatiles observed in comets based on their trapping in the form of clathrate hydrates in the solar nebula. The formation of clathrates is calculated from the statistical thermodynamics of Lunine and Stevenson (1985, Astrophys. J. Suppl. 58, 493-531), and occurs in an evolutionary turbulent solar nebula described by the model of Hersant et al. (2001, Astrophys. J. 554, 391-407). It is assumed that clathrate hydrates were incorporated into the icy grains that formed cometesimals. The strong depletion of the N₂ molecule with respect to CO observed in some comets is explained by the fact that CO forms clathrate hydrates much more easily than does N₂. The efficiency of this depletion, as well as the amount of trapped CO, depends upon the amount of water ice available in the region where the clathration took place. This might explain the diversity of CO abundances observed in comets. The same theory, applied to the trapping of volatiles around 5 AU, explains the enrichments in Ar, Kr, Xe, C, and N with respect to the solar abundance measured in the deep troposphere of Jupiter [Gautier et al 2001a] and [Gautier et al 2001b].  相似文献   

Keck AO observations of Io in and out of eclipse     

Imke de Pater  Franck Marchis  Henry G. Roe  James R. Graham 《Icarus》2004,169(1):250-263

We present adaptive optics (AO) observations of Io taken with the W.M. Keck II telescope on 18 December 2001 (UT) before the satellite went into eclipse, and while it was in Jupiter's shadow. Making these kind of Io-in-eclipse observations, as well as the associated data reduction and analysis are challenging; hence one focus of the paper is to explain the methods and tools used for these data sets. For the sunlit images Io itself was used as the wavefront reference source, while nearby Ganymede was used as reference ‘star’ when Io was in eclipse. Observations were obtained in K′-, L′-, and M-bands. The sunlit images have been deconvolved using MISTRAL. The Io-in-eclipse data were deconvolved with IDAC and MISTRAL. The former gives better results, both in absolute photometry and in matching the original images. We determined the flux densities of the hot spots from the original Io-in-eclipse data with StarFinder, as well as from the deconvolved images by integrating the intensity over the relevant areas. We determined the highly anisoplanatic PSF via a FFT method from the original data, and used this in StarFinder and as a starting PSF for IDAC and MISTRAL. We derived temperatures and areal coverage of all 19 spots detected in both K′- and L′-band images of Io-in-eclipse. We also determined temperatures and areal coverage of the hot spots visible on the L′- and M-band images of sunlit Io. Most volcanoes contain a compact hot ‘core’ (?10 km² at 600-800 K) within a larger area at lower temperatures (e.g., ∼10²-10⁴ km² at 300-500 K). The total heat flow contributed by these active volcanoes is 0.2 W m⁻², ∼8% of the average global heat flow measured at 5-20 μm by Veeder et al. [J. Geophys. Res. 99 (1994) 17095].  相似文献   

The legacy of Venus Express: highlights from the first European planetary mission to Venus     

Pierre?DrossartEmail author  Franck?Montmessin 《Astronomy and Astrophysics Review》2015,23(1):5

The ESA/Venus Express mission spent more than 8 years in orbit around Venus to extensively study its atmosphere, ionosphere and plasma environment and unveil new aspects of its surface. Extensive reviews of the work of Venus Express are underway, to cover in-depth studies of the new face of Venus revealed by Venus Express and ground-based concurrent observations. This paper intends to give a summarized and wide overview of some of the outstanding results in all the science areas studied by the mission. This paper will first review the main aspects of the mission and its instrumental payload. Then, a selection of results will be reviewed from the outermost layers interacting with the Solar wind, down to the surface of Venus. As Venus Express is already considered by space agencies as a pathfinder for the future of Venus exploration, perspectives for future missions will be given, which will have to study Venus not only from orbital view, but also down to the surface to solve the many remaining mysteries of the sister planet of the Earth.  相似文献   

Enhanced seamount location database for the western and central Pacific Ocean: Screening and cross-checking of 20 existing datasets     

Valrie Allain  Julie-Anne Kerandel  Serge Andrfouët  Franck Magron  Malcolm Clark  David S. Kirby  Frank E. Muller-Karger 《Deep Sea Research Part I: Oceanographic Research Papers》2008,55(8):1035-1047

Seamounts are habitats of considerable interest in terms of conservation and biodiversity, and in terms of fisheries for bentho-pelagic and pelagic species. Twenty previously compiled datasets including seamount/underwater feature lists, bathymetric maps and emerged feature maps from different sources (ship-derived and satellite altimetry-derived) at different spatial scales (from individual cruise to worldwide satellite data) were gathered in order to compile an enhanced list of underwater features for parts of the western and central Pacific Ocean (WCPO). The KL04 dataset [Kitchingman, A., and Lai, S., 2004. Inferences on potential seamount locations from mid-resolution bathymetric data. Fisheries Centre Research Reports 12 (5), 7–12], listing seamount positions and depths as calculated from satellite altimetry-derived bathymetry, provided the baseline data for this study as it covered the entire region of interest and included summit depth information. All KL04 potential seamounts were cross-checked with other datasets to remove any atolls and islands that had been incorrectly classified as seamounts, to add seamounts undetected by KL04, to update the overall database (geolocation, depth, elevation, and name) and to compile a 12-class typology of the different types of underwater features. Of the 4626 potential seamounts identified in KL04, 719 were multiple identifications of the same large underwater features and 373 (10%) were actually emerged banks, atolls and islands, leaving 3534 actual underwater features. Conversely, 487 underwater features were documented in other datasets but not registered by KL04. The screening of all the potential WCPO seamounts produced a final list of 4021 underwater features with agreed upon position and information. This enhanced list should have many applications in oceanography, biodiversity conservation and studies of the influence of seamounts on pelagic ecosystems and fisheries.  相似文献   

Preliminary observations on pollution of the sea bed and disturbance of sub-littoral communities in northern Brittany by oil from the Amoco Cadiz     

Louis Cabioch  Jean-Claude Dauvin  Franck Gentil 《Marine pollution bulletin》1978,9(11):303-307

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Toward objective rockfall trajectory simulation using a stochastic impact model   总被引：3，自引：0，他引：3  

Franck Bourrier  Luuk Dorren  Franois Nicot  Frdric Berger  Flix Darve 《Geomorphology》2009,110(3-4):68-79

The accuracy of rockfall trajectory simulations depends to a large extent on the calculation of the rebound of falling boulders on different parts of a slope where rockfalls could occur. The models commonly used for rebound calculation are based on restitution coefficients, which can only be calibrated subjectively in the field. To come up with a robust and objective procedure for rebound calculation, a stochastic impact model associated with an objective field data collection method was developed and tested in this study. The aims of this work were to assess the adequacy of this approach and to evaluate the minimum amount of field data required to obtain simulation results with a satisfactory level of predictability. To achieve these objectives, the rebound calculation procedure developed was integrated into a three-dimensional rockfall simulation model, and the simulated results were compared with those obtained from field rockfall experiments. For rocky slopes, the simulations satisfactorily predict the experimental results. This approach is advantageous because it combines precise modelling of the mechanisms involved in the rebound and of their related variability with an objective field data collection procedure which basically only requires collecting the mean size of soil rocks. The approach proposed in this study therefore constitutes an excellent basis for the objective probabilistic assessment of rockfall hazard.  相似文献   

Large static problem in numerical limit analysis: A decomposition approach     

Zied Kammoun  Franck Pastor  Hichem Smaoui  Joseph Pastor 《国际地质力学数值与分析法杂志》2010,34(18):1960-1980

A general decomposition approach for the static method of limit analysis is proposed. It is based on piecewise linear stress fields, on a partition into finite element sub‐problems and on a specific coordination of the subproblem stress fields through auxiliary interface problems. The final convex optimization problems are solved using nonlinear interior point programming methods. As validated for the compressed bar with Tresca/von Mises materials in plane strain, this method appears rapidly convergent, so that very large problems with millions of constraints and variables can be solved. Then the method is applied to the classical problem of the stability of a Tresca vertical cut: the static bound to the stability factor is improved to 3.7752, a value to be compared with the recent best upper bound 3.7776. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

A source study of PM in Saxony by Size-Segregated Characterisation     

H.?HerrmannEmail author  E.?Brüggemann  U.?Franck  T.?Gnauk  G.?L?schau  K.?Müller  A.?Plewka  G.?Spindler 《Journal of Atmospheric Chemistry》2006,55(2):103-130

Airborne particulate matter in Saxony (Germany) was investigated at three different sites (central urban, urban outskirts, rural) during a winter (1999/2000) and a summer (2000) campaign. PM was collected simultaneously at all three sites using five-stage Berner impactors. Besides size-segregated chemical particle characterisation and mass closure source apportionment of the particle components, especially of the carbonaceous fraction was an aim of the study. Source apportionment was performed exclusively on the basis of experimental data without support of models considering a set of basic assumptions and logical deductions. The derived simple equations permit to differentiate the carbonaceous fraction in traffic, domestic heating (winter) and biogenic (summer) contributions.The total carbon (TC) in the smallest particle size range (Dp_aer = 0.05-0.14μm) at the urban site, contributing 88% to the mass in that class, was completely attributed to traffic emissions. For the particle size range Dp_aer = 0.42-1.2 μm (50-60% of the total mass) TC was attributed to traffic (67%) and domestic heating (33%) in winter and to traffic (82%) and biogenic origin (18%) in summer.Size-segregated determination of alkanes revealed that these compounds were mainly of biogenic origin in summer and of anthropogenic origin in winter considering the carbon preference index (CPI_odd). Particulate PAHs found in winter samples originated mainly from domestic heating and not from traffic emissions.The method described cannot provide complete results, but the demonstrated source apportionment can be helpful to assess a given situation with regard to possible steps against the exceeding of the EU limit of the PM₁₀ mass concentration of 50 μg m⁻³.  相似文献   

西菲律宾海末次冰期以来的浊流沉积及其古环境意义   总被引：3，自引：2，他引：1       下载免费PDF全文

党皓文  翦知湣  Franck Bassinot 《第四纪研究》2009,29(6):1078-1085

菲律宾海西部吕宋岛岸外MD98－2188钻孔揭示末次冰期以来发生过数次浊流沉积事件。研究发现浊流沉积层具有密度高、颜色亮度大等物理特征,含有较多粗沉积组分和翼足类化石碎片,说明其来源于浅海沉积物。本文运用AMS 14C测年和浮游有孔虫氧同位素建立精细的年龄模式,发现浊流沉积层段主要与末次盛冰期、冰期Heinrich变冷事件以及氧同位素4期等低海平面时期相对应,推测与千年尺度北半球气候冷期相关的海平面快速上升可能是西菲律宾海浊流沉积的触发原因。这对于认识快速气候变化的环境后果和开展西菲律宾海晚第四纪地层划分对比都有重要意义。  相似文献