A case study of the mesoscale dynamics in the North-Western Mediterranean Sea: a combined data–model approach     

Karen Guihou  Julien Marmain  Yann Ourmières  Anne Molcard  Bruno Zakardjian  Philippe Forget 《Ocean Dynamics》2013,63(7):793-808

The Northern current is the main circulation feature of the North-Western Mediterranean Sea. While the large-scale to mesoscale variability of the northern current (NC) is well known and widely documented for the Ligurian region, off Nice or along the Gulf of Lions shelf, few is known about the current instabilities and its associated mesoscale dynamics in the intermediate area, off Toulon. Here, we took advantage of an oceanographic cruise of opportunity, the start of a HF radar monitoring programme in the Toulon area and the availability of regular satellite sea surface temperature and chlorophyll a data, to evaluate the realism of a NEMO-based regional high-resolution model and the added value brought by HF radar. The combined analysis of a 1/64° configuration, named GLAZUR64, and of all data sets revealed the occurrence of an anticyclonic coastal trapped eddy, generated inside a NC meander and passing the Toulon area during the field campaign. We show that this anticyclonic eddy is advected downstream along the French Riviera up to the study region and disturbs the Northern current flow. This study aims to show the importance of combining observations and modelling when dealing with mesoscale processes, as well as the importance of high-resolution modelling.  相似文献   

Sampling epifauna, a necessity for a better assessment of benthic ecosystem functioning: an example of the epibenthic aggregated species Ophiothrix fragilis from the Bay of Seine     

Lozach S  Dauvin JC  Méar Y  Murat A  Davoult D  Migné A 《Marine pollution bulletin》2011,62(12):2753-2760

Sampling the sea bottom surface remains difficult because of the surface hydraulic shock due to water flowing through the gear (i.e., the bow wave effect) and the loss of epifauna organisms due to the gear’s closing mechanism. Slow-moving mobile epifauna, such as the ophiuroid Ophiothrix fragilis, form high-density patches in the English Channel, not only on pebbles like in the Dover Strait or offshore Brittany but also on gravel in the Bay of Seine (>5000 ind m⁻²). Such populations form high biomasses and control the water transfer from the water column to the sediment. Estimating their real density and biomass is essential for the assessment of benthic ecosystem functioning using trophic web modelling. In this paper, we present and discuss the patch patterns and sampling efficiency of the different methods for collecting in the dense beds of O. fragilis in the Bay of Seine. The large Hamon grab (0.25 m⁻²) highly under-estimated the ophiuroid density, while the Smith McIntyre appeared adequate among the tested sampling grabs. Nowadays, diving sampling, underwater photography and videos with remote operated vehicle appear to be the recommended alternatives to estimate the real density of such dense slow-moving mobile epifauna.  相似文献   

A Compilation of Silicon,Rare Earth Element and Twenty‐One other Trace Element Concentrations in the Natural River Water Reference Material SLRS‐5 (NRC‐CNRC)     

Delphine Yeghicheyan  Cécile Bossy  Martine Bouhnik Le Coz  Chantal Douchet  Guy Granier  Alexie Heimburger  Francois Lacan  Aurélie Lanzanova  Tristan C. C. Rousseau  Jean‐Luc Seidel  Mickaël Tharaud  Frédéric Candaudap  Jérôme Chmeleff  Christophe Cloquet  Sophie Delpoux  Marie Labatut  Rémi Losno  Catherine Pradoux  Yann Sivry  Jeroen E. Sonke 《Geostandards and Geoanalytical Research》2013,37(4):449-467

The natural river water certified reference material SLRS‐5 (NRC‐CNRC) was routinely analysed in this study for major and trace elements by ten French laboratories. Most of the measurements were made using ICP‐MS. Because no certified values are assigned by NRC‐CNRC for silicon and 35 trace element concentrations (rare earth elements, Ag, B, Bi, Cs, Ga, Ge, Li, Nb, P, Rb, Rh, Re, S, Sc, Sn, Th, Ti, Tl, W, Y and Zr), or for isotopic ratios, we provide a compilation of the concentrations and related uncertainties obtained by the participating laboratories. Strontium isotopic ratios are also given.  相似文献   

Deglaciation history at the Alpine-Mediterranean transition (Argentera-Mercantour,SW Alps) from 10Be dating of moraines and glacially polished bedrock     

Yann Rolland  Romain Darnault  Régis Braucher  Didier Bourlès  Carole Petit  Stéphane Bouissou  ASTER Team 《地球表面变化过程与地形》2020,45(2):393-410

Estimating the extent and age of the last glacial maxima as well as the chronology of glacial recessions in various environmental contexts is key to source-to-sink studies and paleoclimate reconstructions. The Argentera-Mercantour massif is located at the transition between the Alps and the Mediterranean Sea, therefore, its deglaciation chronology can be compared to the sediment budget of the Var River basin. Based on 13 new cosmic-ray exposure (CRE) beryllium-10 (¹⁰Be) datings performed on moraines and polished crystalline bedrocks and 22 reassessed ¹⁰Be CRE ages from similar altitude nearby steep basement surfaces, and from a lake sediment core, we can constrain the deglaciation chronology of the Argentera-Mercantour massif. These data allow for the first time to fully reconstruct the deglaciation history at the scale of the entire massif in agreement with a major glacier recession at c. 15 ka, at the onset of Bølling transition between the Oldest and Older Dryas. Main deglaciation of the upper slopes [2700–2800 m above sea level (a.s.l.)] occurred after the Last Glacial Maximum (LGM) at 20.8–18.6 ka, followed by the main deglaciation of the lower slopes (2300 m a.s.l.) at 15.3–14.2 ka. Finally, the flat polished surfaces above 2600 m a.s.l. and the zones confined within narrow lateral valleys were likely affected by progressive ice melting of remaining debris covered glaciers and moraine erosion following the Younger Dryas re-advance stage between 12 and 8–9 ka. At lower elevations, the Vens Lake located at 2300 m a.s.l., allows evidence of the onset of lake sedimentation at c. 14 ka and a transition towards a vegetated environment that mainly occurred before 8 ka. Moraine final stabilization at 5 ka might reflect denudation acceleration during the Holocene humid phase. This contribution reveals a glacier–climate relationship more sensitive to warming phases in the southern Alps highlighted by a major decrease of glaciers after c. 15 ka. This major deglaciation is correlated with a 2.5-fold decrease of sediment discharge of rivers into the Mediterranean Sea. © 2019 John Wiley & Sons, Ltd.  相似文献   

Multistatic estimation of high-frequency radar surface currents in the region of Toulon     

Dumas  Dylan  Gramoullé  Anthony  Guérin  Charles-Antoine  Molcard  Anne  Ourmières  Yann  Zakardjian  Bruno 《Ocean Dynamics》2020,70(12):1485-1503

Ocean Dynamics - The high-frequency radar coastal network in Toulon operates in multistatic mode for the monitoring of the ocean circulation in the Northwestern Mediterranean Sea. With 2...  相似文献   

Stable isotope contents of porewater in a claystone formation (Tournemire, France): assessment of the extraction technique and preliminary results     

Yann Moreau-Le Golvan  Jean-Luc Michelot  Jean-Yves Boisson 《Applied Geochemistry》1997,12(6):739-745

Claystones are one of the types of geological formations that are considered for the isolation of radioactive wastes. The study of water transfer through these rocks comes up against a lot of difficulties. Among them is the problem of extracting representative samples of interstitial water from indurated claystones with very low water contents (usually less than 10% vol.). The vacuum distillation technique considered here for samples from the Tournemire site (Toarcian argillite formation), is one of the few usable techniques to extract water from this type of rock in order to perform stable isotope investigations on porewater. Tests have shown that the isotope water content is not only influenced by the yield of extraction and the temperature of distillation (as already known), but also by the rain size and the contact time between the crushed sample and the atmosphere. This affects particularly¹⁸O data.The first isotopic results on the Tournemire claystones suggest a meteoric origin for its interstitial water. Data show a depletion in heavy isotopes with respect to present day meteoric water, that could suggest a recharge under climatic conditions cooler than at present. A clear link appears between the isotope contents of water and the structural context: interstitial waters of rock samples taken in the fractured zone of the massif seem to have been affected by a secondary process (evaporation or water-rock exchange) leading to the enrichment in heavy isotopes.  相似文献   

Evaluation of the recharge processes and impacts of irrigation on groundwater using CFCs and radiogenic isotopes in the Silao-Romita basin, Mexico     

Axel Horst  Jürgen Mahlknecht  Broder J. Merkel  Ramon Aravena  Yann R. Ramos-Arroyo 《Hydrogeology Journal》2008,16(8):1601-1614

The recharge processes in the overexploited aquifer of the Silao Romita basin, central Mexico, were investigated by means of gaseous tracers (chlorofluorocarbons, CFCs) and radioactive isotopes (C-14, tritium). CFC concentrations varied between 0.06 and 12 pmol/l (CFC-11), 0.03 and 1.7 pmol/l (CFC-12), and <0.01 and 0.23 pmol/l (CFC-113). CFC concentrations are controlled by irrigation return flow which became apparent by the comparison with tritium. Tritium activities ranged from 0 to 3.5 TU. The calculated mean residence times of 70 to more than 300 years are considerably lower than the ages estimated based on the CFCs data. These data showed that CFCs were not appropriate for groundwater dating in this particular area but the CFCs were suitable as a qualitative measure of the magnitude of irrigation return flow which proved to be a significant source of recharge in the irrigated areas. Radiocarbon activities were in the range of 6–109 pmC. Carbon-13 values varied between –11.9 and –7.2‰ VPDB. Modelling of carbon isotopes with NETPATH along a plausible flow path reveals considerable influences of exchange with soil CO₂ and carbonate dissolution. Radiocarbon data indicate, at least in one case, the existence of groundwaters with residence times of more than 10,000 years.  相似文献   

Textures,trace elements,and Pb isotopes of sulfides from the Haopinggou vein deposit,southern North China Craton: implications for discrete Au and Ag–Pb–Zn mineralization     

Zhan-Ke Li  Jian-Wei Li  David R. Cooke  Leonid Danyushevsky  Lejun Zhang  Hugh O’Brien  Yann Lahaye  Wen Zhang  Hai-Jun Xu 《Contributions to Mineralogy and Petrology》2016,171(12):99

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Hydrological regimes in a tropical valley of New Caledonia (SW Pacific): Impacts of wildfires and invasive fauna     

Caroline Marie Clémence Tramier  Pierre Genthon  Quentin Réginald Camille Paul Delvienne  Nicolas Luc Sauvan  Jean-Jérôme Olivier Cassan  Etienne Ebrard  Pascal Sébastien Dumas  Yann Queffélean 《水文研究》2021,35(3):e14071

In New Caledonia wildfires and invasive mammals (deer and wild pigs) constitute the major agents of land surface degradation. Our study reveals the linkage between land cover and water balance on the northeast coast of New Caledonia (2400 mm annual rainfall) located on a micaschist basement. The hydrological regime of characteristic and representative land surfaces is assessed using a 1-year record from three 100 m² plots each, located in a forest area degraded by an invasive fauna, in a woody savannah which is regularly burned, and in a healthy forest area. The three plots present highly contrasting hydrological regimes, with annual and maximum runoff/rain ratios during a rain event of, respectively, 0.82, 0.16, 0.03, and 2.7, 0.7, 0.2, for the degraded forest, the savannah and the healthy forest. Such results suggest that subsurface flow originating from the contributing area above the degraded forest plot should exfiltrate inside the plot. A conceptual model for the degraded forest plot shows that water exfiltrating inside the plot represents 61% of the observed runoff. In savannahs, water should mainly be transferred downstream by subsurface flow within a thick organic soil layer limited by an impervious clay layer at a 20–30 cm depth. Savannahs are generally located above forests and generate the transfer of rainwater to downslope forests. Exfiltration into the forests can be the result of this transfer and depends on the thickness and permeability of the forest topsoils and on topographic gradients. Water exfiltration in forest areas highly degraded by pigs and deer enhances erosion and increases further degradation. It probably also limits percolation in the areas located downstream by increasing the amount of superficial runoff concentrated in gullies.  相似文献