Impact of environmental parameters on coral reef development and drowning: Forward modelling of the last deglacial reefs from Tahiti (French Polynesia; IODP Expedition #310)     

Claire Seard  Jean Borgomano  Didier Granjeon  Gilbert Camoin 《Sedimentology》2013,60(6):1357-1388

The sedimentological and chronological analysis of the last deglacial reef sequences of Tahiti (French Polynesia), drilled during the Integrated Ocean Drilling Program Expedition 310, provide a high‐resolution data set allowing a well‐constrained forward modelling study. This study represents the first attempt to model in three dimensions the coral reef development of Tahiti during the last deglacial sea‐level rise (23 000 to 6000 cal yr bp ) using the software dionisos developed by IFP Energies nouvelles. It allows the testing of the reconstructed last deglacial sea‐level curve and the different environmental parameters (for example, wave energy and sediment fluxes) that could have influenced the reef development. These last deglacial reef sequences form two prominent ridges occurring seaward of the living barrier reef that consist of successive submerged reefs. These reefs have been prone to drowning because the window of maximum carbonate production rate is inhibited by high water turbidity (sediment supply from a nearby river), shallow depth of wave action and substrate availability. These factors, combined with rapid sea‐level rise, have driven the growth of retrograding reef pinnacles. Local factors (substratum nature, sediment supply and wave energy) were the main processes that induced the drowning of the inner ridge, whereas interplay of local and global factors (acceleration of the sea‐level rise) was responsible for the drowning of the outer ridge. This particular acceleration of sea‐level rise of 16 m between 14·6 ka and 14 ka bp corresponds to meltwater pulse 1A.  相似文献   

News Items     

Jérémie Ory  Sidonie Christophe  Sara Irina Fabrikant  Benedicte Bucher 《The Cartographic journal》2013,50(2):193-203

The process of reading a topographic map requires users to recognize and learn the cartographic symbols of the key (or legend) while interpreting the territory as depicted on the map at a given level of abstraction (the form and nature of features, their saliency and relationships). We present the results of an empirical user study that aims to identify and assess the main graphical characteristics that are used by map users to recognize the design principles which constitute the topographic mapping style adopted by IGN (Institut National de l'Information Géographique et Forestière), France. Our results suggest that 91% of the participants were able to recognize an IGN-France topographic map amongst other topographic map products. We also determine which graphical characteristics play a role in the recognition of this cartographic style, either by visual memory or by visual perception, and identify the representation of relief, including contour lines and shaded relief, as one of the major graphical characteristics of the topographic mapping style of IGN-France. Moreover, the participants of our study considered the representation of touristic POI (points of interest), toponymy, typography, the main roads network, the individual buildings and the forests, to be essential for stylistic recognition.  相似文献   

Linking ground motion measurements and macroseismic observations in France: a case study based on accelerometric and macroseismic databases     

Chloé Lesueur  Michel Cara  Oona Scotti  Antoine Schlupp  Christophe Sira 《Journal of Seismology》2013,17(2):313-333

Comparison between accelerometric and macroseismic observations is made for three M _w?=?4.5 earthquakes, which occurred in north-eastern France and south-western Germany in 2003 and 2004. Scalar and spectral instrumental parameters are processed from the accelerometric data recorded by nine accelerometric stations located between 29 and 180 km from the epicentres. Macroseismic data are based on French Internet reports. In addition to the single questionnaire intensity, analysis of the internal correlation between the encoded answers highlights four predominant fields of questions bearing different physical meanings: (1) “vibratory motions of small objects”, (2) “displacement and fall of objects”, (3) “acoustic noise” and (4) “personal feelings”. Best correlations between macroseismic and instrumental observations are obtained when the macroseismic parameters are averaged over 10-km-radius circles around each station. Macroseismic intensities predicted by published peak ground velocity (PGV)–intensity relationships agree with our observed intensities, contrary to those based on peak ground acceleration (PGA). Correlation between the macroseismic and instrumental data for intensities between II and V (EMS-98) is better for PGV than for PGA. Correlation with the response spectra exhibits clear frequency dependence for all macroseismic parameters. Horizontal and vertical components are significantly correlated with the macroseismic parameters between 1 and 10 Hz, a range corresponding to both natural frequencies of most buildings and high energy content in the seismic ground motion. Between 10 and 25 Hz, a clear lack of correlation between macroseismic and instrumental observations exists. It could be due to a combination of the decrease in the energy signal above 10 Hz, a high level of anthropogenic noise and an increase in variability in soil conditions. Above 25 Hz, the correlation coefficients between the acceleration response spectra and the macroseismic parameters are close to the PGA correlation level.  相似文献   

The CartACom model: transforming cartographic features into communicating agents for cartographic generalisation     

Cécile Duchêne  Anne Ruas  Christophe Cambier 《International journal of geographical information science》2013,27(9):1533-1562

Our research is concerned with automated generalisation of topographic vector databases in order to produce maps. This article presents a new, agent-based generalisation model called CartACom (Cartographic generalisation with Communicating Agents), dedicated to the treatment of areas of low density but where rubber sheeting techniques are not sufficient because some eliminations or aggregations are needed. In CartACom, the objects of the initial database are modelled as agents, that is, autonomous entities, that choose and apply generalisation algorithms to themselves in order to increase the satisfaction of their constraints as much as possible. The CartACom model focuses on modelling and treating the relational constraints, defined as constraints that concern a relation between two objects. In order to detect and assess their relational constraints, the CartACom agents are able to perceive their spatial surroundings. Moreover, to make the good generalisation decisions to satisfy their relational constraints, they are able to communicate with their neighbours using predefined dialogue protocols. Finally, a hook to another agent-based generalisation model – AGENT – is provided, so that the CartACom agents can handle not only their relational constraints but also their internal constraints. The CartACom model has been applied to the generalisation of low-density, heterogeneous areas like rural areas, where the space is not hierarchically organised. Examples of results obtained on real data show that it is well adapted for this application.  相似文献   

Spaceborne ultraviolet 251–384 nm spectroscopy of a meteor during the 1997 Leonid shower     

Peter Jenniskens  Ed Tedesco  Jayant Murthy  Christophe O. Laux  Stephen Price 《Meteoritics & planetary science》2002,37(8):1071-1078

Abstract— We used the ultraviolet to visible spectrometers onboard the midcourse space experiment to obtain the first ultraviolet spectral measurements of a bright meteor during the 1997 Leonid shower. The meteor was most likely a Leonid with a brightness of about‐2 magnitude at 100 km altitude. In the region between 251 and 310 nm, the two strongest emission lines are from neutral and ionized magnesium. Ionized Ca lines, indicative of a hot T ? 10 000 K plasma, are not detected. The Mg and Mg+ line intensity ratio alone does not yield the ionization temperature, which can be determined only by assuming the electron density. A typical air plasma temperature of T = 4400 K would imply a very high electron density: n_e = 2.2 times 10¹⁸ m‐³, but at chondritic abundances of Fe/Mg and Si/Mg ? 1. For a more reasonable local‐thermodynamic‐equilibrium (LTE) air plasma electron density, the Mg and Mg+ line ratio implies a less than chondritic Fe/Mg = 0.06 abundance ratio and a cool non‐LTE T = 2830 K ionization temperature for the ablation vapor plasma. The present observations do not permit a choice between these alternatives. The new data provide also the first spectral confirmation of the presence of molecular OH and NO emission in meteor spectra.  相似文献   

The 1995–2002 Long-Term Monitoring of Comet C/1995 O1 (HALE–BOPP) at Radio Wavelength     

Biver  Nicolas  Bockelée-Morvan  Dominique  Colom  Pierre  Crovisier  Jacques  Henry  Florence  Lellouch  Emmanuel  Winnberg  Anders  Johansson  Lars E.B.  Gunnarsson  Marcus  Rickman  Hans  Rantakyrö  Fredrik  Davies  John K.  Dent  William R.F.  Paubert  Gabriel  Moreno  Raphaël  Wink  Jörn  Despois  Didier  Benford  Dominic J.  Gardner  Matt  Lis  Dariusz C.  Mehringer  David  Phillips  Thomas G.  Rauer  Heike 《Earth, Moon, and Planets》2002,90(1-4):5-14

The bright comet Hale–Bopp provided the first opportunity to follow the outgassing rates of a number of molecular species over a large range of heliocentric distances. We present the results of our observing campaign at radio wavelengths which began in August 1995 and ended in January 2002. The observations were carried out with the telescopes of Nançay, IRAM, JCMT, CSO and, since September 1997, SEST. The lines of nine molecules (OH, CO, HCN, CH₃OH, H₂CO, H₂S, CS, CH₃CN and HNC) were monitored. CS, H₂S, H₂CO, CH₃CN were detected up to r_h= 3–4 AU from the Sun, while HCN and CH₃OH were detected up to 6 AU. CO, which is the main driver of cometary activity at heliocentric distances larger than 3–4 AU, was last detected in August 2001, at r_h= 14 AU. The gas production rates obtained from this programme contain important information on the nature of cometary ices, their thermal properties and sublimation mechanisms.Line shapes allow to measure gas expansion velocities, which, at large heliocentric distances, might be directly connected to the temperature of the nucleus surface. Inferred expansion velocity of the gas varied as r_h ^-0.4 within 7 AU from the Sun, but remained close to 0.4 km s^-1 further away. The CO spectra obtained at large r_hare strongly blueshifted and indicative of an important day-to-night asymmetry in outgassing and expansion velocity. The kinetic temperature of the coma, estimated from the relative intensities of the CH₃OH and CO lines, increased with decreasing r_h, from about 10 K at 7 AU to 110 K around perihelion.  相似文献   

Chemical Composition Diversity Among 24 Comets Observed At Radio Wavelengths     

Biver  Nicolas  Bockelée-Morvan  Dominique  Crovisier  Jacques  Colom  Pierre  Henry  Florence  Moreno  Raphaël  Paubert  Gabriel  Despois  Didier  Lis  Dariusz C. 《Earth, Moon, and Planets》2002,90(1-4):323-333

We present a comparative study on molecular abundances in comets basedon millimetre/submillimetre observations made with the IRAM 30-m,JCMT, CSO and SEST telescopes. This study concerns a sample of 24comets (6 Jupiter-family, 3 Halley-family, 15 long-period) observedfrom 1986 to 2001 and 8 molecular species (HCN, HNC, CH₃CN,CH₃OH, H₂CO, CO, CS, H₂S). HCN was detected in all comets,while at least 2 molecules were detected in 19 comets. From the sub-sample of comets for which contemporary H₂O productionrates are available, we infer that the HCN abundance relative to water variesfrom 0.08% to 0.25%. With respect to other species, HCN is the moleculewhich exhibits the lowest abundance variation from comet to comet. Therefore,production rates relative to that of HCN can be used for a comparative study ofmolecular abundances in the 19 comets. It is found that: CH₃OH/HCN varies from ≤ 9 to 64; CO/HCN varies from ≤ 24 to 180; H₂CO/HCN varies between 1.6 and 10; and H₂S/HCN varies between 1.5 and 7.6. This study does not show any clear correlation between the relative abundancesand the dynamical origins of the comets, or their dust-to-gas ratios.  相似文献   

The thermal evolution of the donors in AM Canum Venaticorum binaries     

Christopher J. Deloye  Ronald E. Taam  Christophe Winisdoerffer  Gilles Chabrier 《Monthly notices of the Royal Astronomical Society》2007,381(2):525-542

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Collision-induced galaxy formation: semi-analytical model and multiwavelength predictions     

Christophe Balland  Julien E. G. Devriendt  Joseph Silk 《Monthly notices of the Royal Astronomical Society》2003,343(1):107-115

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Exploring national decarbonization pathways and global energy trade flows: a multi-scale analysis     

Steve Pye  Christophe McGlade  Chris Bataille  Gabrial Anandarajah  Amandine Denis-Ryan  Vladimir Potashnikov 《Climate Policy》2016,16(4):S92-S109

The role of fossils fuels in national economies will change radically over the next 40 years under a strong climate regime. However, capturing this changing role through national-based analyses is challenging due to the global nature of fossil fuel demand and resulting trade patterns. This article sets out the limitations of existing national-scale decarbonization analyses in adequately capturing global conditions and explores how the introduction of a global modelling framework could provide vital insights, particularly for those countries that are dependent on fossil fuel exports or imports.

The article shows that fossil fuel use will significantly decline by 2050, although gas will have an important transition role. This leaves large fossil fuel exporters exposed, the extent of which is determined by mitigation action in different regions and especially by the pathways adopted by the larger Asian economies. We find that global-scale models provide critical insights that complement the more detailed national analyses and should play a stronger role in informing deep decarbonization pathways (DDPs). They also provide an important basis for exploring key uncertainties around technology uptake, mitigation rates and how this plays out in the demand for fossil fuels. However, use of global models also calls for improved representation of country specifics in global models, which can oversimplify national economic and political realities. Using both model scales provides important insights that are complementary but that can challenge the other’s orthodoxy. However, neither can replace the other’s strengths.

Policy relevance:

In recent years, how global fossil fuel markets will evolve under different climate regimes has been subject to much debate and analysis. This debate includes whether investments in fossil fuel production still make sense or will be exposed in the future to liabilities associated with high carbon prices. This is important for governments who need to develop coherent policy in relation to fossil fuel sectors and their role as drivers of economic growth and in providing for domestic energy needs. This article argues that national analyses need to be fully cognizant of the global-scale transition, which can be informed by using a multi-scale modelling approach.  相似文献