• NEANIAS Atmospheric Research Community

[1] The ability of a three-dimensional sigma coordinate free surface model to reproduce the interfacial layer between the Atlantic and Mediterranean waters in the Strait of Gibraltar is verified. The model uses a coastal-following curvilinear orthogonal grid that includes the Gulf of Cadiz and the Alboran Sea, with very high resolution in the strait (less than 500 m). It is forced by imposing the two major semidiurnal tidal components (M2 and S2) along the Atlantic and the Mediterranean open boundaries. The main experiment covers an entire spring-neap cycle (fortnight period). Results show that the model is able to reproduce a thick interfacial layer that carries a substantial fraction of the total transport. The interfacial thickness is strongly modulated by tidal forcing that enhances the vertical exchanges between layers. In order to take into account the thick interfacial layer, a three-layer approximation is used to study the hydraulics. Results show that the exchange regime is intermittently maximal due to cyclically controlled regions over Camarinal Sill and within Tarifa Narrows. The analysis has been repeated in a two-layer framework to evaluate the impact of the introduction of an interfacial layer on the calculation of hydraulics. In the two-layer approximation, there is not any controlled region extending on the whole cross section, so the exchange is always submaximal. Concluding, the two-layer approximation underestimates hydraulic controls in the strait respect to the three-layer approach.

International audience; This study is the first synthesis of chemical composition and stable isotopes values for the Kerguelen archipelago waters. The stable isotope values for rainfall and river waters in the Kerguelen archipelago allow a calculation of the Local Meteoric Water Line (δD rainfall = 8.43 x δ18O rainfall + 11) and a summer runoff line (δD river drainage = 7.45 x δ18O river drainage + 6). Surface waters with low- ion concentrations, chlorine facies and stable isotope values infiltrate through fractures and lava flows recharging deeper groundwaters. Thermal groundwater with low- (7 to 50 °C) and high- (50 to 100 °C) temperatures emerges in different localities in the volcanic archipelago. The low-temperature thermal waters might represent a mixture of high-temperature water with rainfall, thermal gradient changes or shallower infiltration compared to that for high-temperature thermal waters. The Rallier du Baty and Val Travers areas contain geothermal fluids with high-temperature springs, fumaroles and a large water flow. In the Rallier du Baty, the major ion chemistry and O, H, C and S stable isotope ratio of low (7 to 50 °C) temperature spring waters in Rallier du Baty area demonstrate a geothermal-system recharged by meteoric water (δD H2O liquid = 7.0 x δ18O H2O liquid + 0.5) rather than sea water. The chemical and isotopic compositions of elevated temperature spring waters (50 to 100 °C) have a long and complex history of meteoric water interacting with cooling magmas (δD H2O liquid = 1.78 x δ18O H2O liquid – 23). Surficial precipitation of aragonite, kaolinite, pyrite, native sulfur attest to a long livied geothermal system. A temperature of the geothermal reservoir has been estimated between 193 and 259 °C by cation geothermometry. The combination of minerals observed, major ion composition of water with thermodynamic modeling and stable isotope data suggest a geothermal system with a series of water/rock interactions from 50 to 250 °C. The conductive cooling of rising of H2O−CO2-rich fluids have produced a H2O−CO2 phase separation with the precipitation of secondary minerals.

The magnetic meridional component of the thermospheric neutral wind is derived from the F2 layer height measured from ionograms collected at Kokubunji, Japan and compared with the winds measured by the middle and upper atmosphere radar at Shigaraki, Japan and the winds predicted by the empirical Horizontal Wind Model 1990 (HWM90). Good agreement is found between the ionosonde and the radar winds. This agreement supports the previous finding of the radar study that the winds over Japan are smaller in amplitude than the winds reported elsewhere by a factor of 1.5–2. On the other hand, disagreement is found at some local times between the ionosonde and HWM90 winds. The ionosonde winds in the period from 1986 to 1988 are, on average, poleward in the daytime and equatorward in the nighttime. The daytime-nighttime difference remains at about 100 m/s summer or winter, but this diurnal pattern is superposed upon a daily average drift of about 10 m/s southward in summer and 10 m/s northward in winter, suggesting a consistent summer-to-winter circulation pattern. This limited study validates the ionosonde wind method as applied at Japanese longitudes and opens the way for comprehensive studies of the thermospheric wind over Japan from the long and continuous ionogram libraries from the Japanese ionosonde chain.

Dating Carbon Radiocarbon dating is the best way to determine the age of samples that contain carbon and that are younger than ∼50,000 years, the limit of precision for the method. There are several factors that complicate such age determinations, however, some of the most important of which include variability of the 14 C production in the atmosphere (which affects organic samples whose radiocarbon inventories are derived from atmospheric CO 2 ), surface ocean reservoir effects (which affect marine samples that acquire their radiocarbon signatures from seawater), and variable dead carbon fraction effects (which affect speleothems that derive their carbon from groundwaters). Bronk Ramsey et al. (p. 370 ; see the Perspective by Reimer ) avoid the need to make such assumptions, reporting the 14 C results of sediments from Lake Suigetsu, Japan. Analysis of terrestrial plant macrofossils in annually layered datable sediments yielded a direct record of atmospheric radiocarbon for the entire measurable interval up to 52.8 thousand years ago.

The different deposition periods in sedimentary geological environment have made the build-up and estimation of soil organic matter ambiguous to study. Soil organic matter has received global attention in the ambience of international policy regarding environmental health and safety. This research was to understand the inter-relationship between soil organic matter and bulk density, saturated hydraulic conductivity (Ksat), total, air-filled and capillary porosities for organic matter estimation, via different multiple linear regression functions (i.e., leapbackward, leap forward, leapseq and lmStepAIC), in soils developed over the sedimentary geological environment. Eight mapping units were obtained in Ishibori, Agoi Ibami and Mfamosing via digital elevation model. Two pits were sited within each mapping unit, and 53 soil samples were used for the study. In soils over shale–limestone–sandstone, two pits were sited, six in alluvium, four in sandstone–limestone and four in limestone. Overall correlation between SOM with Ksat (r = 0.626) and BD (r = − 0.588) was significant (p < 0.001). The strongest correlation was obtained for SOM with BD (r = − 0.783) and Ksat (r = 0.790) in soils over limestone. In contrast, soils over shale–limestone and sandstone geological environment gave the weakest relationship (r < 0.6). Linear regression gave a similar prediction output. The best performing was leapbackward (RMSE = 11.50%, R2 = 0.58, MAE = 8.48%), which produced a smaller error when compared with leap forward, leapseq and lmStepAIC functions in organic matter estimation. Therefore, we recommend applying leapback linear regression when estimating soil organic variation with physical soil properties for solving soil–environmental issues towards sustainable crop production in southeast Nigeria.

A heave compensation system combined with a vibration absorber and accumulator is proposed, with regard to the requirement for poly-metallic nodule mining systems at an ocean depth of 6,000 m in Ch...

In order to improve the accuracy of the strength assessment of operating reinforced concrete structures, it is rational to use the model with a discrete location of reinforcing bars with the actual characteristics of adhesion to concrete reinforcement. The problem of pulling the reinforcing bar from the concrete block is relevant for the practice, as it represents the most widespread method of experimental evaluation of characteristics of reinforced-concrete bond behavior. Fracture of bond during the pulling of rebar from concrete is a complex multistep process, characterized with the presence of inhomogeneous and inelastic deformation, the rupture of adhesive bonds, the initiation and propagation of cracks of different shape and orientation, the presence of contact and tribological phenomena. The nonlinear finite-element solutions of the pulling the reinforcing bar from the concrete block problem have been obtained by using various models of bond behavior and concrete cracking. The comparison between the obtained numerical results and experimental data has been presented and discussed. The first part of the article is devoted to the models taking into account the discontinuity of the connection. The second part is concerned with the models without explicitly taking into account discontinuities.