Carbonyl Sulphide (OCS) Variability with Latitude in the Atmosphere

Abstract

Carbonyl sulphide (OCS) is an important precursor of sulphate aerosols and consequently a key species in stratospheric ozone depletion. The SPectromètre InfraRouge d'Absorption à Lasers Embarqués (SPIRALE) and shortwave infrared (SWIR) balloon-borne instruments have flown in the tropics and in the polar Arctic, and ground-based measurements have been performed by the Qualité de l'Air (QualAir) Fourier Transform Spectrometer in Paris. Partial and total columns and vertical profiles have been obtained to study OCS variability with altitude, latitude, and season. The annual total column variation in Paris reveals a seasonal variation with a maximum in April–June and a minimum in November–January. Total column measurements above Paris and from SWIR balloon-borne instrument are compared with several MkIV measurements, several Network for the Detection of Atmospheric Composition Change (NDACC) stations, aircraft, ship, and balloon measurements to highlight the OCS total column decrease from tropical to polar latitudes. OCS high-resolution in situ vertical profiles have been measured for the first time in the altitude range between 14 and 30?km at tropical and polar latitudes. OCS profiles are compared with Atmospheric Chemistry Experiment (ACE) satellite measurements and show good agreement. Using the correlation between OCS and N₂O from SPIRALE, the OCS stratospheric lifetime has been accurately determined. We find a stratospheric lifetime of 68?±?20 years at polar latitudes and 58?±?14 years at tropical latitudes leading to a global stratospheric sink of 49?±?14?Gg?S?y^?1.     

阿尔金北缘地区剥离断层控矿和金矿成因——以大平沟金矿床为例

阿尔金北缘大平沟金矿床是近年来在阿尔金山地区新发现的首例岩金矿床。为了阐明其矿床地质特征及其成因,采用构造解析与矿主档学研究相结合的方法。结果表明,（1）金矿物主要为金－银系列矿物,成色在915－946之间,金含量与K2O、Fe2O3呈正相关关系;（2）变粒岩、强片理化变粒岩、含金石英脉和无矿化纯净石英脉的稀土元素配分型式具有相似性;（3）主要成矿期温度范围198－290℃,为中温热液矿床;（4）成矿深度为1.77-2.68km;（5）氢氧同位素组成具有以岩浆水为主的特征。由此认为,大平沟金矿床是受阿尔金北缘断裂－剥离断层控制的金矿床,是该地区金矿找矿的方向。     

Multi-fidelity meta-modeling for reservoir engineering - application to history matching

Defining representative reservoir models usually calls for a huge number of fluid flow simulations, which may be very time-consuming. Meta-models are built to lessen this issue. They approximate a scalar function from the values simulated for a set of uncertain parameters. For time-dependent outputs, a reduced-basis approach can be considered. If the resulting meta-models are accurate, they can be called instead of the flow simulator. We propose here to investigate a specific approach named multi-fidelity meta-modeling to reduce further the simulation time. We assume that the outputs of interest are known at various levels of resolution: a fine reference level, and coarser levels for which computations are faster but less accurate. Multi-fidelity meta-models refer to co-kriging to approximate the outputs at the fine level using the values simulated at all levels. Such an approach can save simulation time by limiting the number of fine level simulations. The objective of this paper is to investigate the potential of multi-fidelity for reservoir engineering. The reduced-basis approach for time-dependent outputs is extended to the multi-fidelity context. Then, comparisons with the more usual kriging approach are proposed on a synthetic case, both in terms of computation time and predictivity. Meta-models are computed to evaluate the production responses at wells and the mismatch between the data and the simulated responses (history matching error), considering two levels of resolution. The results show that the multi-fidelity approach can outperform kriging if the target simulation time is small. Last, its potential is evidenced when used for history matching.     

Gravity and S-wave modelling across the Jan Mayen Ridge,North Atlantic; implications for crustal lithology

The horizontal components from fourteen Ocean Bottom Seismometers deployed along four profiles focused along the western margin of the Jan Mayen microcontinent, North Atlantic, have been modelled with regard to S-waves, based on P-wave models obtained earlier. The seismic models have furthermore been constrained by 2D gravity modelling. High V _p/V _s-ratios (2.3–7.9) within the Cenozoic sedimentary section are attributed to significant porosities, whereas V _p/V _s-ratios in the order of 1.9–2.2 for the Mesozoic and Paleozoic sedimentary rocks indicate shale-dominated lithology throughout the area. The eastern side of the Jan Mayen Ridge is interpreted as a passive, volcanic margin, based on relatively high crustal V _p/V _s-ratios (1.9), whereas lower V _p/V _s-ratios (1.75–1.8) suggest the presence of intermediate composition crust and non-volcanic margin on the western side of the ridge. In the westernmost part of the Jan Mayen Basin, slightly increased upper mantle V _p/V _s-ratios may indicate some degree of serpentization of upper mantle peridotites.     

Evolution des hydrocarbures et des populations bactériennes et microphytiques dans les sédiments des marais maritimes de l'ile grande pollués par l'Amoco cadiz: 2—Evolution des peuplements microphytiques

In this work we attempt to estimate the short- and long-term effects of the Amoco Cadiz oil spill on benthic microalgal populations (cyanophytes and diatoms) which, under natural conditions, live on upper layers of ‘schorres’ soils or of ‘slikke’ muds in the Ile Grande salt marsh system (Côtes du Nord, France). These populations were completely destroyed in 1978 in the oil-affected sites. Ubiquitous species settled fairly rapidly on intertidal polluted muds (tidal flat). The chlorophyll a content values reached 100 μg g⁻¹ dry sediment, i.e. 1000 mg m⁻² in 1980. Conversely, the salt marsh soils are still much less densely repopulated 3 years after the Amoco Cadiz grounding—especially when they are infrequently flooded (3 to 40 μg Chl.a g⁻¹, i.e. 40 to 270 mg m⁻²). Some of these soils remain ten times less populated than reference stations.     

All washed up: spatial and temporal variation in the wash-up and fate of chondrichthyan egg cases along a section of the Garden Route,South Africa

Washed-up chondrichthyan egg cases were collected along three different sandy beaches around Plettenberg Bay, South Africa, between April 2016 and March 2017. GPS location was recorded upon collection, and, after being soaked in fresh water for 12 hours, egg cases were identified to species level. Additionally, boreholes, damage, biofouling and state of the hatchling slit were recorded. The hatching success of each egg case was inferred from these factors. Over the year, 6 996 egg cases of nine species were collected. Egg cases of the tiger catshark Halaelurus natalensis had the highest hatching rate at 70%. Egg cases of the leopard catshark Poroderma pantherinum had the highest predation rate at 57%. Season had no significant effect either on overall egg-case counts or on per-species counts. Location, however, significantly affected the overall egg-case counts, as well as per-species counts, with the exceptions of H. natalensis and the St Joseph Callorhinchus capensis. The results of this study provide insight into chondrichthyan species occurrence and spatial variation along a section of the Garden Route in the Western Cape Province and can act as a baseline for future research.     

The Hospitalet gneiss dome (Pyrenees) revisited: lateral flow during Variscan transpression in the middle crust

A new structural and kinematic study of the Hospitalet dome (Pyrenees) is presented. This dome corresponds to the eastern half of an EW‐trending antiformal structure made of an orthogneissic core intruded by granitoids, partly covered by Upper Proterozoic to Lower Ordovician metapelites. Its Variscan evolution can be split into four stages: (i) development of a strong high temperature pervasive deformation associated with subhorizontal foliations and lineations, and with non‐coaxial top‐to‐the‐east kinematics; (ii) formation of a south‐verging overturned megafold; (iii) emplacement of calc‐alkaline granitoids; and (iv) formation of mylonitic bands on the southern border of the dome, with reverse dextral kinematics. The flat lying pervasive high‐T deformation is interpreted as a large lateral flow developed in a dextral transpressive regime inducing an important uncoupling between the middle and upper crusts. The next stages happened in a progressive deformation in the same transpressive regime.     

Monitoring degradation in arid and semi-arid forests and woodlands: The case of the argan woodlands (Morocco)

Arid and semi-arid forests and woodlands (hereafter called «dryland forests»), in spite of their ecological and social importance, have received little attention in land change studies. Growing evidence shows that these forests have been receding at very high rates in many places, suggesting a need for a better understanding of the processes and causes of dryland forest degradation. Changes in the extent of dryland forests are debated in part because estimates of forest and woodland areas in drylands are uncertain. Causal explanations of the degradation tend to draw on the literature on desertification and tropical deforestation, and to emphasize either local or remote, and either social or biophysical drivers. This study contributes to a better understanding of dryland forest degradation as a basis for conservation policies. Firstly, we argue that monitoring arid and semi-arid forests and woodlands using area estimates may lead to an underestimation of the severity of change because tree density change often exceeds area change. Secondly, we argue that the analysis of degradation processes in these multifunctional landscapes should integrate both local and remote, and both social and biophysical factors. We use a case study of degradation in the argania woodlands in semi-arid to arid Southwest Morocco to test these two claims. We used gridded tree counts on aerial photographs and satellite images to estimate forest change between 1970 and 2007, and we tested several possible causes of change on the basis of original socio-economic field surveys and climatic and topographic data. We found that forest density declined by 44.5% during this period, a figure that is significantly underestimated if forest area change is used as a measure of degradation. Increasing aridity and, to a lesser extent, fuelwood extraction were related to forest decline. No effect of grazing by local livestock was found.