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Ruitton S Javel F Culioli JM Meinesz A Pergent G Verlaque M 《Marine pollution bulletin》2005,50(10):1061-1068
The introduced green alga Caulerpa racemosa var. cylindracea has been rapidly spreading in the Mediterranean Sea since 1990. It was first observed in France in 1997 (Marseilles). In early 2004, the stretch of the French Mediterranean coastline and the surface area affected by the invasion were estimated at about 83 km and 4014 ha, respectively. The depth range of colonized areas was usually 10-35 m depth. Shallow (0-10 m) and deep (down to 40 m) dense meadows were rarely observed. In contrast to the dead matte of Posidonia oceanica, which constituted the most widely colonized substratum, dense P. oceanica meadows and fine sand with large ripple-marks were not invaded. Few rocky areas were colonized and coarse sand bottoms were usually colonized below 20 m depth. All the colonized areas were exposed to human activities and more than 40% were fishing areas. Mild climate, suitable substrata, presence of vectors of dispersal and absence of efficient biological control make the French Mediterranean coast particularly vulnerable to the further spread of the alga. 相似文献
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Alkali-calcic and alkaline post-orogenic (PO) granite magmatism: petrologic constraints and geodynamic settings 总被引：30，自引：0，他引：30
The end of an orogenic Wilson cycle corresponds to amalgamation of terranes into a Pangaea and is marked by widespread magmatism dominated by granitoids. The post-collision event starts with magmatic processes still influenced by subducted crustal materials. The dominantly calc-alkaline suites show a shift from normal to high-K to very high-K associations. Source regions are composed of depleted and later enriched orogenic subcontinental lithospheric mantle, affected by dehydration melting and generating more and more K- and LILE-rich magmas. In the vicinity of intra-crustal magma chambers, anatexis by incongruent melting of hydrous minerals may generate peraluminous granitoids bearing mafic enclaves. The post-collision event ends with emplacement of bimodal post-orogenic (PO) suites along transcurrent fault zones. Two suites are defined, (i) the alkali-calcic monzonite–monzogranite–syenogranite–alkali feldspar granite association characterised by [biotite+plagioclase] fractionation and moderate [LILE+HFSE] enrichments and (ii) the alkaline monzonite–syenite–alkali feldspar granite association characterised by [amphibole+alkali feldspar] fractionation and displaying two evolutionary trends, one peralkaline with sodic mafic mineralogy and higher enrichments in HFSE than in LILE, and the other aluminous biotite-bearing marked by HFSE depletion relative to LILE due to accessory mineral precipitation. Alkali-calcic and alkaline suites differ essentially in the amounts of water present within intra-crustal magma chambers, promoting crystallisation of various mineral assemblages. The ultimate enriched and not depleted mantle source is identical for the two PO suites. The more primitive LILE and HFSE-rich source rapidly replaces the older orogenic mantle source during lithosphere delamination and becomes progressively the thermal boundary layer of the new lithosphere. Present rock compositions are a mixture of major mantle contribution and various crustal components carried by F-rich aqueous fluids circulating within convective cells created around magma chambers. In favourable areas, PO suites pre-date a new orogenic Wilson cycle. 相似文献
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Regnauld Hervé Binois Sandrine Fouqué Christophe Lemasson Loic 《Geologie en Mijnbouw》1998,77(3-4):323-332
In the framework of the European project 'Climate change and coastal evolution in Europe', the microscale (< 1 year) morphological evolution of beaches in Brittany (W France) has been monitored for some years and linked to immediate forcings, the first one being tides (with a 13-m tidal range), and the second storm intensity. For the same sites, a mesoscale (decades) evolution was reconstructed from air photographs and historical data. The evolution is forced first of all by human activities, and secondly by climatic shift: wind direction changes and average wind velocity evolution. These results were used to build and calibrate a model of coastal behaviour. The model is based on a simple sediment cell (input – transit – output) and simulates the movements of volumes of sands under successive morphodynamic processes. Each of these processes is modelled (in terms of volume exchanges) and parameterized by the relevant atmospheric element. Thus, the model is not deterministic but simulates different probabilities for atmospheric events and morphological response. The model runs for one year and produces realistic sediment accumulation values and coastal retreat rates. When run for half a century, results are also quite comparable to the field data. Storm frequency changes appear to be an important element for the evolution, but the main and first forcing is the availability of sediment. 相似文献
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Sean L. Bruinsma Christoph Förste Sandrine Mulet Marie-Hélène Rio Oleg Abrikosov Jean-Charles Marty 《Marine Geodesy》2016,39(3-4):238-255
The impact of GOCE Satellite Gravity Gradiometer data on gravity field models was tested. All models were constructed with the same Laser Geodynamics Satellite (LAGEOS) and Gravity Recovery and Climate Experiment (GRACE) data, which were combined with one or two of the diagonal gravity gradient components for the entire GOCE mission (November 2009 to October 2013). The Stokes coefficients were estimated by solving large normal equation (NE) systems (i.e., the direct numerical approach). The models were evaluated through comparisons with the European Space Agency's (ESA) gravity field model DIR-R5, by GPS/Leveling, GOCE orbit determination, and geostrophic current evaluations. Among the single gradient models, only the model constructed with the vertical ZZ gradients gave good results that were in agreement with the formal errors. The model based only on XX gradients is the least accurate. The orbit results for all models are very close and confirm this finding. All models constructed with two diagonal gradient components are more accurate than the ZZ-only model due to doubling the amount of data and having two complementary observation directions. This translates also to a slower increase of model errors with spatial resolution. The different evaluation methods cannot unambiguously identify the most accurate two-component model. They do not always agree, emphasizing the importance of evaluating models using many different methods. The XZ gravity gradient gives a small positive contribution to model accuracy. 相似文献
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The stakes for alleviating poverty and avoiding unbridled climate change are inextricably linked. Climate change impacts will slow down and may even reverse trends in poverty reduction. The pathways consistent with global warming of no more than 2?°C require strategies for poverty alleviation to make allowance for the constraint of low-carbon development. Existing climate funds have failed to target poverty alleviation as a high-priority strategy for adaptation or as a component of low-carbon development. This article proposes a funding window as part of the Green Climate Fund in order to foster synergies targeting greater satisfaction of basic needs, while making allowance for adaptation and mitigation. This financial mechanism is based on indicators of the satisfaction of basic needs and could respond to the claims of the developing countries, which see alleviating poverty as the first priority in climate negotiations. It defines a country continuum, given that there are poor people everywhere; all developing countries are therefore eligible with a mechanism of this sort.Policy relevanceThe Intergovernmental Panel on Climate Change (IPCC) calls for substantial emissions reductions and adaptation strategies over the next decades to reduce the high risks of severe impacts of climate change over the 21st century. Industrialized countries and developing countries alike recognize the need to mitigate climate change and to adapt to it. But they face many challenges that lead to an ‘emissions gap’ between an emissions level consistent with the 2?°C increase limit and the voluntary pledges that they have made thus far in the climate negotiations (United Nations Environment Programme. (2014). The Emissions Gap Report 2014. A UNEP synthesis report). In this arena, many developing countries underline that their first domestic priority is the satisfaction of basic needs. In the run-up to the next climate negotiations at the 21st Conference of the Parties (COP 21) in Paris, the proposed poverty-adaptation-mitigation funding window could contribute to alleviate the conflict between development and climate goals in developing countries. In this sense, it could spur developing countries to integrate more ambitious emissions limitations pledges into their Intended Nationally Determined Contributions. This could in turn entice industrialized countries to act similarly. In the end, it could pave the way to an ambitious climate agreement in Paris at COP 21. 相似文献
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Sandrine Bernard-Trottolo B. Campistron A. Druilhet F. Lohou F. Saïd 《Boundary-Layer Meteorology》2004,111(2):181-224
The TRAC98 experimental campaign (Turbulence Radar Aircraft Cells) devoted to coherent structures analysis took place over the Beauce plain (France) during summer 1998. It allowed us to collect a large dataset of airborne measurements in addition to various ground measurements. This study aims at diagnosing the occurrence of coherent structures within the atmospheric boundary layer (ABL) through airborne measurements. The statistical analysis performed as a first step from turbulent parameters underlined the homogeneity of the ABL over the Beauce plain. However mixed-layer scaling failed at the top of the ABL, even when taking into account the entrainment rate. Coherent structures were detected through the analysis of ABL isotropy, using the opportunity of sampling with two perpendicular crossing planes, one of them being aligned with the wind. This approach allowed us to determine an organization scheme of the ABL for three of the five flights (ARAT30, MIV30 and MIV27). For the ARAT30 flight, the analysis was pursued by focusing on measurements of fluctuations in the inner flight legs. In this way, the low-level cloud cover has been investigated from the downward visible radiation (VISD). The results indicated an anisotropy of the horizontal cloud size. Secondly, the variations of some parameters were analysed through lagged correlation functions. This allowed us to infer relationships between the vertical velocity, VISD, mixing ratio and lifting condensation level. Length scales have also been extracted, and confirmed the ABL organization during the ARAT30 flight. Finally, the anisotropy observed in various flights has been investigated with respect to the underestimation of the latent heat fluxes revealed by the imbalance of the surface energy budget. 相似文献
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Pascal Podwojewski Jean Louis Janeau Sandrine Caquineau Jeffrey Hughes 《地球表面变化过程与地形》2020,45(13):3202-3215
The formation of deep gullies (called ‘dongas’ locally) in rangeland in KwaZulu-Natal Province in South Africa is a natural phenomenon. These U-shaped, very wide gullies have considerable lateral expansion due to the episodic collapse of sidewalls. The dongas have developed in duplex soils such as Luvisols and Lixisols formed on Permian sedimentary rocks or unconsolidated Quaternary colluvium. This study combined morphological, mineralogical and chemical characterization with measurements of grain-size content, structural stability and the complete shrinkage curve to detect changes in soil properties of the different horizons located in the gully banks. The different soil horizons present clear and sharp differences in physical and mineralogical properties. The topsoil with complete grass cover is very resistant to soil detachment. However, the leached E horizon and the BC horizon have low structural stability. The soil profile down to and including the Bt horizon contains exclusively illite in the clay fraction, while the BC colluvial layer and the C horizon (mudstone) contain expandable interstratified illite–smectite. The Bt horizon has a high water content at saturation and high shrinkage, while the BC and C horizons have a high residual shrinkage and a very low water content at saturation. Because this type of gully expansion is not significantly linked to slope value or the stream power index (SPI) at the gully head, to land-use change, high rainfall intensities or the threshold of concentrated runoff being exceeded at the gully head, other causes were investigated. It was concluded that the heterogeneity between horizons with different mineralogical properties and structural stabilities, soil types and parent material, anisotropic water-saturation and shrink-swell properties are of major importance. This heterogeneity between different soil horizon morphologies and their physical properties can explain why the relationship between the critical slope and the drainage area for gully initiation showed a threshold for gullying much lower than that found elsewhere. © 2020 John Wiley & Sons, Ltd. 相似文献
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Christopher E. Holloway Allison A. Wing Sandrine Bony Caroline Muller Hirohiko Masunaga Tristan S. L’Ecuyer David D. Turner Paquita Zuidema 《Surveys in Geophysics》2017,38(6):1199-1236
Convective self-aggregation, the spontaneous organization of initially scattered convection into isolated convective clusters despite spatially homogeneous boundary conditions and forcing, was first recognized and studied in idealized numerical simulations. While there is a rich history of observational work on convective clustering and organization, there have been only a few studies that have analyzed observations to look specifically for processes related to self-aggregation in models. Here we review observational work in both of these categories and motivate the need for more of this work. We acknowledge that self-aggregation may appear to be far-removed from observed convective organization in terms of time scales, initial conditions, initiation processes, and mean state extremes, but we argue that these differences vary greatly across the diverse range of model simulations in the literature and that these comparisons are already offering important insights into real tropical phenomena. Some preliminary new findings are presented, including results showing that a self-aggregation simulation with square geometry has too broad distribution of humidity and is too dry in the driest regions when compared with radiosonde records from Nauru, while an elongated channel simulation has realistic representations of atmospheric humidity and its variability. We discuss recent work increasing our understanding of how organized convection and climate change may interact, and how model discrepancies related to this question are prompting interest in observational comparisons. We also propose possible future directions for observational work related to convective aggregation, including novel satellite approaches and a ground-based observational network. 相似文献