The Multiscale TROPIcal CatchmentS critical zone observatory M-TROPICS dataset III: Hydro-geochemical monitoring of the Mule Hole catchment,south India     

Jean Riotte  Laurent Ruiz  Stéphane Audry  Benjamin Baud  Jean-Pierre Bedimo Bedimo  Laurie Boithias  Jean-Jacques Braun  Bernard Dupré  Jean-Louis Duprey  Mikael Faucheux  Christelle Lagane  Jean-Christophe Marechal  Hemanth Moger  Mandalagiri Subbarayappa Mohan Kumar  Harshad Parate  Olivier Ribolzi  Emma Rochelle-Newall  Buvaneshwari Sriramulu  Murari Varma  Muddu Sekhar 《水文研究》2021,35(5):e14196

Despite the importance of tropical ecosystems for climate regulation, biodiversity, water and nutrient cycles, only a few Critical Zone Observatories (CZOs) are located in the tropics. Among these, most are in humid climates, while very few data exist for semi-arid and sub-humid climates, due to the difficulty of estimating hydro-geochemical balances in catchments with ephemeral streams. We contribute to fill this gap by presenting a meteorological and hydro-geochemical dataset acquired at the Mule Hole catchment (4.1 km²), a pristine dry deciduous forest located in a biosphere reserve in south India. The dataset consists of time series of variables related to (i) meteorology, including rainfall, air temperature, relative humidity, wind speed and direction, and global radiation, (ii) hydrology, including water level and discharge at the catchment outlet, (iii) hydrogeology, including manual (monthly) and/or automated (from 15 min to hourly) groundwater levels in nine piezometers and (iv) geochemistry, including suspended sediment content in the stream and chemical composition of rainfall (event based), groundwater (monthly sampling) and stream water (storm events, 15 min to hourly frequency with an automatic sampler). The time series extend from 2003 to 2019. Measurement errors are minimized by frequent calibration of sensors and quality checks, both in the field and in the laboratory. Despite these precautions, several data gaps exist, due to occasional access restriction to the site and instrument destruction by wildlife. Results show that large seasonal and interannual variations of climatic conditions were reflected in the large variations of stream flow and groundwater recharge, as well as in water chemical composition. Notably, they reveal a long-term evolution of groundwater storage, suggesting hydrogeological cycles on a decadal scale. This dataset, alone or in combination with other data, has already allowed to better understand water and element cycling in tropical dry forests, and the role of forest diversity on biogeochemical cycles. As tropical ecosystems are underrepresented by Critical Zone Observatories, we expect this data note to be valuable for the global scientific community.  相似文献   

A mechanism for the multidecadal modulation of ENSO teleconnection with Europe   总被引：1，自引：1，他引：0  

Jorge López-Parages  Belén Rodríguez-Fonseca  Laurent Terray 《Climate Dynamics》2015,45(3-4):867-880

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Evidence for and relationship between recent distributed extension and halokinesis in the Farasan Islands,southern Red Sea,Saudi Arabia     

Khalid?A.?AlmalkiEmail author  Laurent?Ailleres  Peter?G.?Betts  Rashad?A.?Bantan 《Arabian Journal of Geosciences》2015,8(10):8753-8766

This paper presents a structural evolution study of the Farasan Bank using an integration of field work, remote sensing data, and regional Bouguer gravity data interpretation. The architecture of the Farasan Islands is influenced by normal faults parallel to the Red Sea rift axis delineating a series of graben and asymmetric half-graben structures as well as salt domes. Geological data suggest that the negative gravity anomaly over the Farasan Bank reflects thick salt deposits. The gravity data shows a general NW-SE trend with the main negative anomaly coincident with the Farasan Islands. Gravity data together with seismic reflection data suggest that salt diapirs are elongated and parallel to the main rift orientation (NW-SE). This indicates that salt deposition and diapirism was controlled by rift-related basement structures. Forward modeling of gravity data constrained by marine seismic reflection interpretation reveals that the evaporites directly overlie the basement in most places. No pre-evaporite formation was detected. Integration of the modeling with field observations and interpretations suggests that the Farasan Islands are in an area of active extension. Extension and salt diapirism on the flank of the mid-ocean ridge is likely to be synchronous with renewed spreading at 5 Ma.  相似文献   

Diagnosing the Dynamic and Thermodynamic Effects for the Exceptional 2020 Summer Rainy Season in the Yangtze River Valley     

Na WEN  Shujie LIU  Laurent Z.X.LI 《Journal of Meteorological Research》2022,(1):26-36

An exceptional rainy season occurred in the Yangtze River valley of eastern China in June–July 2020. The relative importance of the dynamic and thermodynamic ef...  相似文献   

Distribution and geological control of mud volcanoes and other fluid/free gas seepage features in the Mediterranean Sea and nearby Gulf of Cadiz     

Jean Mascle  Flore Mary  Daniel Praeg  Laetitia Brosolo  Laurent Camera  Silvia Ceramicola  Stéphanie Dupré 《Geo-Marine Letters》2014,34(2-3):89-110

Existing knowledge on the distribution of mud volcanoes (MVs) and other significant fluid/free gas-venting features (mud cones, mud pies, mud-brine pools, mud carbonate cones, gas chimneys and, in some cases, pockmark fields) discovered on the seafloor of the Mediterranean Sea and in the nearby Gulf of Cadiz has been compiled using regional geophysical information (including multibeam coverage of most deepwater areas). The resulting dataset comprises both features proven from geological sampling, or in situ observations, and many previously unrecognized MVs inferred from geophysical evidence. The synthesis reveals that MVs clearly have non-random distributions that correspond to two main geodynamic settings: (1) the vast majority occur along the various tectono-sedimentary accretionary wedges of the Africa-Eurasia subduction zone, particularly in the central and eastern Mediterranean basins (external Calabrian Arc, Mediterranean Ridge, Florence Rise) but also along its westernmost boundary in the Gulf of Cadiz; (2) other MVs characterize thick depocentres along parts of the Mesozoic passive continental margins that border Africa from eastern Tunisia to the Levantine coasts, particularly off Egypt and, locally, within some areas of the western Mediterranean back-arc basins. Meaningfully accounting for MV distribution necessitates evidence of overpressured fluids and mud-rich layers. In addition, cross-correlations between MVs and other GIS-based data, such as maps of the Messinian evaporite basins and/or active (or recently active) tectonic trends, stress the importance of assessing geological control in terms of the presence, or not, of thick seals and potential conduits. It is contended that new MV discoveries may be expected in the study region, particularly along the southern Ionian Sea continental margins.  相似文献   

A statistical�Cdynamical scheme for reconstructing ocean forcing in the Atlantic. Part I: weather regimes as predictors for ocean surface variables     

Christophe Cassou  Marie Minvielle  Laurent Terray  Claire P��rigaud 《Climate Dynamics》2011,36(1-2):19-39

The links between the observed variability of the surface ocean variables estimated from reanalysis and the overlying atmosphere decomposed in classes of large-scale atmospheric circulation via clustering are investigated over the Atlantic from 1958 to 2002. Daily 500?hPa geopotential height and 1,000?hPa wind anomaly maps are classified following a weather-typing approach to describe the North Atlantic and tropical Atlantic atmospheric dynamics, respectively. The algorithm yields patterns that correspond in the extratropics to the well-known North Atlantic-Europe weather regimes (NAE-WR) accounting for the barotropic dynamics, and in the tropics to wind classes (T-WC) representing the alteration of the trades. 10-m wind and 2-m temperature (T2) anomaly composites derived from regime/wind class occurrence are indicative of strong relationships between daily large-scale atmospheric circulation and ocean surface over the entire Atlantic basin. High temporal correlation values are obtained basin-wide at low frequency between the observed fields and their reconstruction by multiple linear regressions with the frequencies of occurrence of both NAE-WR and T-WC used as sole predictors. Additional multiple linear regressions also emphasize the importance of accounting for the strength of the daily anomalous atmospheric circulation estimated by the combined distances to all regimes centroids in order to reproduce the daily to interannual variability of the Atlantic ocean. We show that for most of the North Atlantic basin the occurrence of NAE-WR generally sets the sign of the ocean surface anomaly for a given day, and that the inter-regime distances are valuable predictors for the magnitude of that anomaly. Finally, we provide evidence that a large fraction of the low-frequency trends in the Atlantic observed at the surface over the last 50?years can be traced back, except for T2, to changes in occurrence of tropical and extratropical weather classes. All together, our findings are encouraging for the prospects of basin-scale ocean dynamical downscaling using a weather-typing approach to reconstruct forcing fields for high resolution ocean models (Part II) from coarse resolution climate models.  相似文献   

Impact of sediment-induced stratification and turbulence closures on sediment transport and morphological modelling   总被引：1，自引：0，他引：1  

Laurent O. Amoudry  Alejandro J. Souza 《Continental Shelf Research》2011,31(9):912-928

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Controls on ostracod valve geochemistry, Part 1: Variations of environmental parameters in ostracod (micro-)habitats     

Laurent Decrouy  Torsten Walter Vennemann 《Geochimica et cosmochimica acta》2011,75(22):7364-7379

The variations of environmental conditions (T°, pH, δ¹³C_DIC, [DIC], δ¹⁸O, Mg/Ca, and Sr/Ca) of ostracod habitats were examined to determine the controls of environmental parameters on the chemical and isotopic composition of ostracod valves. Results of a one-year monitoring of environmental parameters at five sites, with depths of between 2 and 70 m, in Lake Geneva indicate that in littoral to sub-littoral zones (2, 5, and 13 m), the chemical composition of bottom water varies seasonally in concert with changes in temperature and photosynthetic activity. An increase of temperature and photosynthetic activity leads to an increase in δ¹³C values of DIC and to precipitation of authigenic calcite, which results in a concomitant increase of Mg/Ca and Sr/Ca ratios of water. In deeper sites (33 and 70 m), the composition of bottom water remains constant throughout the year and isotopic values and trace element contents are similar to those of deep water within the lake. The chemical composition of interstitial pore water also does not reflect seasonal variations but is controlled by calcite dissolution, aerobic respiration, anaerobic respiration with reduction of sulphate and/or nitrate, and methanogenesis that may occur in the sediment pores. Relative influence of each of these factors on the pore water geochemistry depends on sediment thickness and texture, oxygen content in bottom as well as pore water. Variations of chemical compositions of the ostracod valves of this study vary according to the specific ecology of the ostracod species analysed, that is its life-cycle and its (micro-)habitat. Littoral species have compositions that are related to the seasonal variations of temperature, δ¹³C values of DIC, and of Mg/Ca and Sr/Ca ratios of water. In contrast, the compositions of profundal species are largely controlled by variations of pore fluids along sediment depth profiles according to the specific depth preference of the species. The control on the geochemistry of sub-littoral species is a combination of controls for the littoral and profundal species as well as the specific ecology of the species.  相似文献   

Natural tracer profiles across argillaceous formations   总被引：2，自引：0，他引：2  

Martin Mazurek  Peter Alt-EppingAdrian Bath  Thomas Gimmi  H. Niklaus WaberStéphane Buschaert  Pierre De Cannière  Mieke De CraenAndreas Gautschi  Sébastien Savoye  Agnès VinsotIsabelle Wemaere  Laurent Wouters 《Applied Geochemistry》2011,26(7):1035-1064

Argillaceous formations generally act as aquitards because of their low hydraulic conductivities. This property, together with the large retention capacity of clays for cationic contaminants, has brought argillaceous formations into focus as potential host rocks for the geological disposal of radioactive and other waste. In several countries, programmes are under way to characterise the detailed transport properties of such formations at depth. In this context, the interpretation of profiles of natural tracers in pore waters across the formations can give valuable information about the large-scale and long-term transport behaviour of these formations. Here, tracer-profile data, obtained by various methods of pore-water extraction for nine sites in central Europe, are compiled. Data at each site comprise some or all of the conservative tracers: anions (Cl⁻, Br⁻), water isotopes (δ¹⁸O, δ²H) and noble gases (mainly He). Based on a careful evaluation of the palaeo-hydrogeological evolution at each site, model scenarios are derived for initial and boundary pore-water compositions and an attempt is made to numerically reproduce the observed tracer distributions in a consistent way for all tracers and sites, using transport parameters derived from laboratory or in situ tests. The comprehensive results from this project have been reported in Mazurek et al. (2009). Here the results for three sites are presented in detail, but the conclusions are based on model interpretations of the entire data set. In essentially all cases, the shapes of the profiles can be explained by diffusion acting as the dominant transport process over periods of several thousands to several millions of years and at the length scales of the profiles. Transport by advection has a negligible influence on the observed profiles at most sites, as can be shown by estimating the maximum advection velocities that still give acceptable fits of the model with the data. The advantages and disadvantages of different conservative tracers are also assessed. The anion Cl⁻ is well suited as a natural tracer in aquitards, because its concentration varies considerably in environmental waters. It can easily be measured, although the uncertainty regarding the fraction of the pore space that is accessible to anions in clays remains an issue. The stable water isotopes are also well suited, but they are more difficult to measure and their values generally exhibit a smaller relative range of variation. Chlorine isotopes (δ³⁷Cl) and He are more difficult to interpret because initial and boundary conditions cannot easily be constrained by independent evidence. It is also shown that the existence of perturbing events such as the activation of aquifers due to uplift and erosion, leading to relatively sharp changes of boundary conditions, can be considered as a pre-requisite to obtain well-interpretable tracer signatures. On the other hand, gradual changes of boundary conditions are more difficult to parameterise and so may preclude a clear interpretation.  相似文献   

Relation between two common localisation methods for the EnKF   总被引：3，自引：0，他引：3  

Pavel Sakov  Laurent Bertino 《Computational Geosciences》2011,15(2):225-237

This study investigates the relation between two common localisation methods in ensemble Kalman filter (EnKF) systems: covariance localisation and local analysis. Both methods are popular in large-scale applications with the EnKF. The case of local observations with non-correlated errors is considered. Both methods are formulated in terms of tapering of ensemble anomalies, which provides a framework for their comparison. Based on analytical considerations and experimental evidence, we conclude that in practice the two methods should yield very similar results, so that the choice between them should be based on other criteria, such as numerical effectiveness and scalability.  相似文献