Correction to: Characterization,modeling, and remediation of karst in a changing environment     

Zexuan Xu  Nicolas Massei  Ingrid Padilla  Andreas Hartmann  Bill Hu 《Environmental Earth Sciences》2018,77(15):560

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Projecting future drought in Mediterranean forests: bias correction of climate models matters!   总被引：1，自引：0，他引：1  

Julien Ruffault  Nicolas K Martin-StPaul  Carole Duffet  Fabien Goge  Florent Mouillot 《Theoretical and Applied Climatology》2014,117(1-2):113-122

Global and regional climate models (GCM and RCM) are generally biased and cannot be used as forcing variables in ecological impact models without some form of prior bias correction. In this study, we investigated the influence of the bias correction method on drought projections in Mediterranean forests in southern France for the end of the twenty-first century (2071–2100). We used a water balance model with two different atmospheric climate forcings built from the same RCM simulations but using two different correction methods (quantile mapping or anomaly method). Drought, defined here as periods when vegetation functioning is affected by water deficit, was described in terms of intensity, duration and timing. Our results showed that the choice of the bias correction method had little effects on temperature and global radiation projections. However, although both methods led to similar predictions of precipitation amount, they induced strong differences in their temporal distribution, especially during summer. These differences were amplified when the climatic data were used to force the water balance model. On average, the choice of bias correction leads to 45 % uncertainty in the predicted anomalies in drought intensity along with discrepancies in the spatial pattern of the predicted changes and changes in the year-to-year variability in drought characteristics. We conclude that the choice of a bias correction method might have a significant impact on the projections of forest response to climate change.  相似文献   

Lipid biomarkers for anaerobic oxidation of methane and sulphate reduction in cold seep sediments of Nyegga pockmarks (Norwegian margin): discrepancies in contents and carbon isotope signatures     

Nicolas Chevalier  Ioanna Bouloubassi  Alina Stadnitskaia  Marie-Hélène Taphanel  Jaap S. Sinninghe Damsté 《Geo-Marine Letters》2014,34(2-3):269-280

Distributions and carbon isotopic compositions of microbial lipid biomarkers were investigated in sediment cores from the G11 and G12 pockmarks in the Nyegga sector of the Storegga Slide on the mid-Norwegian margin to explore differences in depth zonation, type and carbon assimilation mode of anaerobic methane-oxidizing archaea (ANMEs) and associated sulphate-reducing bacteria responsible for anaerobic oxidation of methane (AOM) in these cold seep environments. While the G11 site is characterised by black reduced sediments colonized by gastropods and Siboglinidae tubeworms, the G12 site has black reduced sediments devoid of fauna but surrounded by a peripheral occurrence of gastropods and white filamentous microbial mats. At both sites, bulk sediments contained abundant archaeal and bacterial lipid biomarkers substantially depleted in ¹³C, consisting mainly of isoprenoidal hydrocarbons and dialkyl glycerol diethers, fatty acids and non-isoprenoidal monoalkylglycerol ethers. At the G11 site, down-core profiles revealed that lipid biomarkers were in maximum abundance from 10 cm depth to the core bottom at 16 cm depth, associated with δ¹³C values of ?57 to ?136‰. At the G12 site, by contrast, lipid biomarkers were in high abundance in the upper 5 cm sediment layer, associated with δ¹³C values of ?43 to ?133‰. This suggests that, as expected from the benthic fauna characteristics of the sites, AOM takes place mainly at depth in the G11 pockmark but just below the seafloor in the G12 pockmark. These patterns can be explained largely by variable fluid flow rates. Furthermore, at both sites, a dominance of ANME-2 archaea accompanied by their bacterial partners is inferred based on lipid biomarker distributions and carbon isotope signatures, which is in agreement with recently published DNA analyses for the G11 pockmark. However, the present data reveal high discrepancies in the contents and δ¹³C values for both archaeal and bacterial lipid profiles, implying the possible involvement of at least two distinct AOM-related microbial consortia at the inferred AOM depth zonation of G11 and G12 pockmark sediments. In both sediment cores, the δ¹³C profiles for most archaeal lipids suggest a direct assimilation of dissolved inorganic carbon (DIC) in addition to methane by ANMEs (chemoautotrophy); constant and highly depleted δ¹³C profiles for PMI:3, an archaeal lipid biomarker presumably related to ANME-2, suggest a direct assimilation of ¹³C-depleted methane-derived carbon via AOM (methanotrophy). Evidently, the common approach of investigating lipid biomarker contents and δ¹³C signatures in cold seep sediments does not suffice to precisely discriminate between the carbon assimilation mode for each ANME archaeal group and associated bacteria. Rather, this needs to be combined with further specific labelling studies including different carbon sources (methane carbon, methane-derived organic intermediates and DIC) in order to unravel the metabolic pathways of each microbial consortium involved in AOM (ANME-1 vs. ANME-2 vs. ANME-3 archaeal group and associated bacteria).  相似文献   

Crustal‐scale fluid flow during the tectonic evolution of the Bighorn Basin (Wyoming,USA)     

Nicolas Beaudoin  Nicolas Bellahsen  Olivier Lacombe  Laurent Emmanuel  Jacques Pironon 《Basin Research》2014,26(3):403-435

Stable isotope measurements (O, C, Sr), microthermometry and salinity measurements of fluid inclusions from different fracture populations in several anticlines of the Sevier‐Laramide Bighorn basin (Wyoming, USA) were used to unravel the palaeohydrological evolution. New data on the microstructural setting were used to complement previous studies and refine the fracture sequence at basin scale. The latter provides the framework and timing of fluid migration events across the basin during the Sevier and Laramide orogenic phases. Since the Sevier tectonic loading of the foreland basin until its later involvement into the Laramide thick‐skinned orogeny, three main fracture sets (out of seven) were found to have efficiently enhanced the hydraulic permeability of the sedimentary cover rocks. These pulses of fluid are attested by calcite crystals precipitated in veins from hydrothermal (T > 120 °C) radiogenic fluids derived from Cretaceous meteoric fluids that interacted with the Precambrian basement rocks. Between these events, vein calcite precipitated from formational fluids at chemical and thermal equilibrium with surrounding environment. At basin scale, the earliest hydrothermal pulse is documented in the western part of the basin during forebulge flexuring and the second one is documented in basement‐cored folds during folding. In addition to this East/West diachronic opening of the cover rocks to hydrothermal pulses probably controlled by the tectonic style, a decrease in ^87/86Sr values from West to East suggests a crustal‐scale partially squeegee‐type eastward fluid migration in both basement and cover rocks since the early phase of the Sevier contraction. The interpretation of palaeofluid system at basin scale also implies that joints developed under an extensional stress regime are better vertical drains than joints developed under strike‐slip regime and enabled migration of basement‐derived hydrothermal fluids.  相似文献   

Role of the global oceans and land–atmosphere interaction on summertime interdecadal variability over northern Argentina     

Marcelo Barreiro  Nicolas Díaz  Madeleine Renom 《Climate Dynamics》2014,42(7-8):1733-1753

This study uses experiments with an atmospheric general circulation model (AGCM) to address the role of the oceans and the effect of land–atmosphere coupling on the predictability of summertime rainfall over northern Argentina focusing on interdecadal time scales during 1901–2006. Ensembles of experiments where the AGCM is forced with historical sea surface temperature (SST) in the global, Pacific and tropical-North Atlantic domains are used. The role of land–atmosphere interaction is assessed comparing the output of simulations with active and climatological soil moisture. A maximum covariance analysis between precipitation and SST reveals the impact of the Pacific Decadal Oscillation, the Atlantic Multidecadal Oscillation and the equatorial–tropical South Atlantic on rainfall over northern Argentina. Model simulations further show that while the dominant influence comes from the Pacific basin, the Atlantic influence can explain a large transition from dry to wet decades over northern Argentina during the beginning of the 1970s. Analysis of anomalies before and after the transition reveals an upper level anticyclonic circulation off the Patagonian coast with barotropic structure. This circulation enhances the moisture transport and convergence in northern Argentina and, together with enhanced evaporation, increased the rainfall after 1970. The SST pattern is dominated by cold conditions in the equatorial Atlantic and warm eastern Pacific and South Atlantic. We also found that land–atmosphere interaction leads to a representation of the long term rainfall evolution over northern Argentina that is closer to the observed one. Moreover, it leads to a smaller dispersion among ensemble members, thus resulting in a larger signal-to-noise ratio.  相似文献   

Ocean feedback to tropical cyclones: climatology and processes   总被引：1，自引：0，他引：1  

Swen Jullien  Patrick Marchesiello  Christophe E. Menkes  Jérôme Lefèvre  Nicolas C. Jourdain  Guillaume Samson  Matthieu Lengaigne 《Climate Dynamics》2014,43(9-10):2831-2854

This study presents the first multidecadal and coupled regional simulation of cyclonic activity in the South Pacific. The long-term integration of state-of the art models provides reliable statistics, missing in usual event studies, of air–sea coupling processes controlling tropical cyclone (TC) intensity. The coupling effect is analyzed through comparison of the coupled model with a companion forced experiment. Cyclogenesis patterns in the coupled model are closer to observations with reduced cyclogenesis in the Coral Sea. This provides novel evidence of air–sea coupling impacting not only intensity but also spatial cyclogenesis distribution. Storm-induced cooling and consequent negative feedback is stronger for regions of shallow mixed layers and thin or absent barrier layers as in the Coral Sea. The statistical effect of oceanic mesoscale eddies on TC intensity (crossing over them 20 % of the time) is also evidenced. Anticyclonic eddies provide an insulating effect against storm-induced upwelling and mixing and appear to reduce sea surface temperature (SST) cooling. Cyclonic eddies on the contrary tend to promote strong cooling, particularly through storm-induced upwelling. Air–sea coupling is shown to have a significant role on the intensification process but the sensitivity of TCs to SST cooling is nonlinear and generally lower than predicted by thermodynamic theories: about 15 rather than over 30 hPa °C^?1 and only for strong cooling. The reason is that the cooling effect is not instantaneous but accumulated over time within the TC inner-core. These results thus contradict the classical evaporation-wind feedback process as being essential to intensification and rather emphasize the role of macro-scale dynamics.  相似文献   

Seasonal variability of the equatorial undercurrent termination and associated salinity maximum in the Gulf of Guinea     

Nicolas Kolodziejczyk  Frédéric Marin  Bernard Bourlès  Yves Gouriou  Henrick Berger 《Climate Dynamics》2014,43(11):3025-3046

The termination of the Equatorial Undercurrent (EUC) in the eastern equatorial Atlantic during boreal summer and fall, and the fate of the associated saline water masses, are analyzed from in situ hydrological and currents data collected during 19 hydrographic cruises between 2000 and 2007, complemented by observations from Argo profiling floats and PIRATA moorings, and from a numerical simulation of the Tropical Atlantic Ocean for the period 1993–2007. An intense variability of the circulation and hydrological properties is evidenced from observations in the upper thermocline (24.5–26.2 isopycnal layer) between June and November. During early boreal summer, saline water masses are transported eastward in the upper thermocline to the African coast within the EUC, and recirculate westward on both sides of the EUC. In mid-boreal summer, the EUC weakens in the upper thermocline and the equatorial salinity maximum disappears due to intense mixing with the surface waters during the upwelling season. The extra-equatorial salinity maxima are also partially eroded during the boreal summer, with a slight poleward migration of the southern hemisphere maximum until late boreal summer. The upper EUC reappears in September, feeding again the eastern equatorial Atlantic with saline waters until boreal spring. During December–January, numerical results suggest a second seasonal weakening of the EUC in the Gulf of Guinea, with a partial erosion of the associated equatorial salinity maximum.  相似文献   

Corrected prediction intervals for change detection in paired watershed studies     

Nicholas A. Som  Nicolas P. Zégre  Lisa M. Ganio  Arne E. Skaugset 《水文科学杂志》2013,58(1):134-143

Abstract

Hydrological data may be temporally autocorrelated requiring autoregressive process parameters to be estimated. Current statistical methods for hydrological change detection in paired watershed studies rely on prediction intervals, but the current form of prediction intervals does not include all appropriate sources of variation. Corrected prediction intervals for the analysis of paired watershed study data that include variation associated with covariance and linear model parameter estimation are presented. We provide an example of their application to data from the Hinkle Creek Paired Watershed Study located in the western Cascade foothills of Southern Oregon, USA. Research implications of using the correct prediction limits and incorporating the estimation uncertainty of autoregressive process parameters are discussed.

Editor D. Koutsoyiannis

Citation Som, N.A., Zégre, N.P., Ganio, L.M. and Skaugset, A.E., 2012. Corrected prediction intervals for change detection in paired watershed studies. Hydrological Sciences Journal, 57 (1), 134–143.  相似文献   

Armouring of well cement in H₂S–CO₂ saturated brine by calcite coating – Experiments and numerical modelling     

Nicolas Jacquemet  Jacques Pironon  Vincent Lagneau  Jérémie Saint-Marc 《Applied Geochemistry》2012

The active acid gas (H₂S–CO₂ mixture) injection operations in North America provide practical experience for the operators in charge of industrial scale CO₂ geological storage sites. Potential leakage via wells and their environmental impacts make well construction durability an issue for efficiency/safety of gas geological storage. In such operations, the well cement is in contact with reservoir brines and the injected gas, meaning that gas–water–solid chemical reactions may change the physical properties of the cement and its ability to confine the gas downhole. The cement-forming Calcium silicate hydrates carbonation (by CO₂) and ferrite sulfidation (by H₂S) reactions are expected. The main objective of this study is to determine their consequences on cement mineralogy and transfer ability. Fifteen and 60 days duration batch experiments were performed in which well cement bars were immersed in brine itself caped by a H₂S–CO₂ phase at 500 bar–120 °C. Scanning electron microscopy including observations/analyses and elemental mapping, mineralogical mapping by micro-Raman spectroscopy, X-ray diffraction and water porosimetry were used to characterize the aged cement. Speciation by micro-Raman spectroscopy of brine trapped within synthetic fluid inclusions were also performed. The expected calcium silicate hydrates carbonation and ferrite sulfidation reactions were evidenced. Furthermore, armouring of the cement through the fast creation of a non-porous calcite coating, global porosity decrease of the cement (clogging) and mineral assemblage conservation were demonstrated. The low W/R ratio of the experimental system (allowing the cement to buffer the interstitial and external solution pH at basic values) and mixed species diffusion and chemical reactions are proposed to explain these features. This interpretation is confirmed by reactive transport modelling performed with the HYTEC code. The observed cement armouring, clogging and mineral assemblage conservation suggest that the tested cement has improved transfer properties in the experimental conditions. This work suggests that in both acid gas and CO₂ geological storage, clogging of cement or at least mineral assemblage conservation and slowing of carbonation progress could occur in near-well zones where slight water flow occurs e.g. in the vicinity of caprock shales.  相似文献   

Mg/Ca-paleothermometry in the western Mediterranean Sea on planktonic foraminifer species Globigerina bulloides: Constraints and implications     

Soumaya Boussetta  Nejib Kallel  Franck Bassinot  Laurent Labeyrie  Jean-Claude Duplessy  Nicolas Caillon  Fabien Dewilde  Hélène Rebaubier 《Comptes Rendus Geoscience》2012,344(5):267-276

We generated a high-resolution SST_Mg/Ca record for the surface-dwelling planktonic foraminifera Globigerina bulloides from the core MD99-2346 collected in the Gulf of Lion, and compared it to that obtained using modern analogue techniques applied to fossil foraminiferal assemblages (SST_MAT). The two temperature records display similar patterns during the last 28,000 years but the SST_Mg/Ca estimates are several degrees warmer (∼ +4 °C) than SST_MAT. The temperature shift between SST_Mg/Ca and SST_MAT remained relatively constant over time. This seems to exclude a bias on the Mg/Ca record associated with salinity or secondary Mg-rich calcite encrustation on the foraminiferal tests during early diagenesis. Therefore, anomalously high Mg/Ca suggests either: (1) the empirical equation for G. bulloides of Elderfield and Ganssen (2000) is incorrect; or (2) there is a specific Mediterranean genotypes of G. bulloides for which a specific Mg/Ca-temperature calibration is needed.  相似文献