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PIERRE EXERTIER JOËLLE NICOLAS PHILIPPE BERIO DAVID COULOT PASCAL BONNEFOND OLIVIER LAURAIN 《Marine Geodesy》2013,36(1-2):333-340
The French Transportable Laser Ranging System (FTLRS), a highly transportable Satellite Laser Ranging (SLR) instrument, was set up in Corsica (from January to September 2002) for participating to the JASON-1 altimeter verification phase. In addition to the tracking of oceanographic satellite missions and in order to perform an accurate positioning, the FTLRS also acquired laser ranging data on geodetic satellites, STARLETTE and STELLA essentially. The paper describes the analysis strategy mainly based on the use of a short-arc orbit technique to compute accurate 1 cm local orbits, and then the geocentric positioning (2–3 mm relative to GPS). Finally, we established the JASON-1 absolute calibration value, based on 9 SLR short-arcs (between cycles 1 and 26), at 108.2 ± 8.7 mm; the 10-day repeatability is of 26.1 mm showing that a great accuracy has been reached. 相似文献
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Microbially mediated carbonate precipitation in a hypersaline lake,Big Pond (Eleuthera,Bahamas) 总被引：1，自引：0，他引：1
CHRISTINA GLUNK CHRISTOPHE DUPRAZ OLIVIER BRAISSANT KIMBERLEY L. GALLAGHER ERIC P. VERRECCHIA PIETER T. VISSCHER 《Sedimentology》2011,58(3):720-736
Microbial metabolism impacts the degree of carbonate saturation by changing the total alkalinity and calcium availability; this can result in the precipitation of carbonate minerals and thus the formation of microbialites. Here, the microbial metabolic activity, the characteristics and turnover of the extracellular polymeric substances and the physicochemical conditions in the water column and sediments of a hypersaline lake, Big Pond, Bahamas, were determined to identify the driving forces in microbialite formation. A conceptual model for organomineralization within the active part of the microbial mats that cover the lake sediments is presented. Geochemical modelling indicated an oversaturation with respect to carbonates (including calcite, aragonite and dolomite), but these minerals were never observed to precipitate at the mat–water interface. This failure is attributed to the capacity of the water column and upper layers of the microbial mat to bind calcium. A layer of high Mg‐calcite was present 4 to 6 mm below the surface of the mat, just beneath the horizons of maximum photosynthesis and aerobic respiration. This carbonate layer was associated with the zone of maximum sulphate reduction. It is postulated that extracellular polymeric substances and low molecular weight organic carbon produced at the surface (i.e. the cyanobacterial layer) of the mat bind calcium. Both aerobic and anaerobic heterotrophic microbes consume extracellular polymeric substances (each process accounting for approximately half of the total consumption) and low molecular weight organic carbon, liberating calcium and producing inorganic carbon. The combination of these geochemical changes can increase the carbonate saturation index, which may result in carbonate precipitation. In conclusion, the formation and degradation of extracellular polymeric substances, as well as sulphate reduction, may play a pivotal role in the formation of microbialites both in marine and hypersaline environments. 相似文献
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OLIVIER MOINE DENIS-DIDIER ROUSSEAU PIERRE ANTOINE 《Boreas: An International Journal of Quaternary Research》2005,34(3):363-380
Two malacological sequences sampled in loess sections P1 and P3 of Nussloch (Rhine Valley, Germany) provide the most complete and precise molluscan record of western Europe for the Weichselian Lower and Middle Pleniglacial from about 70 to 34 cal. kyr BP. Qualitative and statistical analyses were performed on 134 mollusc samples. In the most complete Lower Pleniglacial record (P1), malacofauna changes reflect three short phases of vegetation development and climatic improvement related to soils and probably interstadials. A steppe to herb/shrub tundra shift characterizes the Lower-Middle Pleniglacial transition and is followed in both malacological records by the same general environmental trend (decline in vegetation and humidity increase) ending with a new increase in temperature and vegetation cover at the top of P3. In the Middle Pleniglacial, the impact of each shorter climatic change on the malacofauna is less recognizable due to a higher sediment compaction and also to being differently recorded in both sequences as the local topography affects soil water resources, soil and vegetation development and malacofauna adaptation. A comparison shows that the western European biostratigraphical framework can thus be improved by coupling molluscan records from loess sections to pollen sequences. 相似文献
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JULIEN ROSSIGNOL OLIVIER MOINE DENIS-DIDIER ROUSSEAU 《Boreas: An International Journal of Quaternary Research》2004,33(2):145-154
We investigated the Upper Pleistocene mollusc sequence in the loess deposit of Buzzard's Roost, Nebraska, and compared the results with those obtained for Eustis, 50 km to the west. Both sequences show similarities in: (i) stratigraphy and magnetic susceptibility implying identical fluctuations in loess deposition, (ii) biostratigraphy which indicates a succession of cold-and-moist to cold-and-dry conditions, and (iii) an increasing trend in mollusc abundance and diversity of species characterizing a climatic and/or environmental improvement. We interpret the variations in both sequences as related to the advance of the James and Des Moines ice lobes towards both sites, which was synchronous with the retreat of the Laurentide Ice Sheet. The occurrence of hygrophilous species in the mollusc record, from the upper sequences of Buzzard's Roost, suggests a moister environment than in Eustis. Our preliminary comparison of both malacological sequences suggests that regional or local, rather than global, influence prevailed over the Great Plains between 20 and 12 kyr BP. 相似文献
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OLIVIER LEENHARDT 《Geophysical Prospecting》1967,15(3):516-526
The author comments the techniques and methods used in continuous seismic profiling by the Monaco Oceanographic Museum during the last five years. Pinger probe give informations on the Mud layering and thickness. On the shelf or in abyssal plains, boomer and sparker are employed and allow to rise various geological conclusions. South coast of France, continental shelf in the Gulf of Lion, abyssal plain of the Ligurian Sea and Lake of Geneva are the areas concerned to with the results. 相似文献
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Assimilation of image sequences in numerical models 总被引：1，自引：0，他引：1
By OLIVIER TITAUD ARTHUR VIDARD INNOCENT SOUOPGUI FRANÇOIS-XAVIER LE DIMET 《地球，A辑:动力气象学与海洋学》2010,62(1):30-47
Understanding and forecasting the evolution of geophysical fluids is a major scientific and societal challenge. Forecasting algorithms should take into account all the available information on the considered dynamic system. The variational data assimilation (VDA) technique combines all these informations in an optimality system (O.S.) in a consistent way to reconstruct the model inputs. VDA is currently used by the major meteorological centres. During the last two decades about 30 satellites were launched to improve the knowledge of the atmosphere and of the oceans. They continuously provide a huge amount of data that are still underused by numerical forecast systems. In particular, the dynamic evolution of certain meteorological or oceanic features (such as eddies, fronts, etc.) that the human vision may easily detect is not optimally taken into account in realistic applications of VDA. Image Assimilation in VDA framework can be performed using 'pseudo-observation' techniques: they provide apparent velocity fields, which are assimilated as classical observations. These measurements are obtained by certain external procedures, which are decoupled with the considered dynamic system. In this paper, we suggest a more consistent approach, which directly incorporates image sequences into the O.S. 相似文献
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LAURENT BOPP OLIVIER AUMONT SAUVEUR BELVISO PATRICK MONFRAY 《Tellus. Series B, Chemical and physical meteorology》2003,55(1):11-22
Dimethyl sulfide (DMS) is a biogenic compound produced in sea-surface water and outgased to the atmosphere. Once in the atmosphere, DMS is a significant source of cloud condensation nuclei in the unpolluted marine atmosphere. It has been postulated that climate may be partly modulated by variations in DMS production through a DMS-cloud condensation nuclei-albedo feedback. We present here a modelled estimation of the response of DMS sea-water concentrations and DMS fluxes to climate change, following previous work on marine DMS modeling ( Aumont et al., 2002 ) and on the global warming impact on marine biology ( Bopp et al., 2001 ). An atmosphere–ocean general circulation model (GCM) was coupled to a marine biogeochemical scheme and used without flux correction to simulate climate response to increased greenhouse gases (a 1% increase per year in atmospheric CO2 until it has doubled). The predicted global distribution of DMS at 1 × CO2 compares reasonably well with observations; however, in the high latitudes, very elevated concentrations of DMS due to spring and summer blooms of Phaeocystis can not be reproduced. At 2 × CO2 , the model estimates a small increase of global DMS flux to the atmosphere (+2%) but with large spatial heterogeneities (from −15% to +30% for the zonal mean). Mechanisms affecting DMS fluxes are changes in (1) marine biological productivity, (2) relative abundance of phytoplankton species and (3) wind intensity. The mean DMS flux perturbation we simulate represents a small negative feedback on global warming; however, the large regional changes may significantly impact regional temperature and precipitation patterns. 相似文献