Diatom–environment relationships and a transfer function for conductivity in lakes of the Badain Jaran Desert, Inner Mongolia, China

We describe a dataset of 26 modern diatom samples and associated environmental variables from the Badain Jaran Desert, northwest China. The influence of electrical conductivity (EC) and other variables on diatom distribution was explored using multivariate analyses and generalized additive modeling of species response curves. A transfer function was derived for EC, the variable with the largest unique effect on diatom variance, as shown by partial canonical correspondence analysis. Weighted-averaging partial least squares regression and calibration provided the best model, with a high coefficient of determination ( $ {\text{r}}_{\text{boot}}^{2} $  = 0.91) and low prediction error (RMSEP_boot = 0.136 log₁₀ μS cm^?1). To assess its potential for palaeosalinity and palaeoclimate reconstructions, the EC transfer function was applied to fossil diatom assemblages from ²¹⁰Pb-dated short sediment cores collected from two subsaline lakes of the Badain Jaran Desert. The diatom-inferred (DI) EC reconstructions were compared with meteorological data for the past 50 years and with remote sensing data for the period AD 1990–2012. Changes in DI–EC were small and their relationship with climate was weak. Moreover, remote sensing data indicate that the surface areas and water depths of these lakes did not change, which suggests that water loss by evaporation is compensated by groundwater inflow. These results suggest that the response of these lakes to climate change is mediated by non-climatic factors such as the hydrogeological setting, which control recharge from groundwater, and may be non-linear and non-stationary.     

A new approach to define surface/sub-surface transition in gravel beds

The vertical structure of river beds varies temporally and spatially in response to hydraulic regime, sediment mobility, grain size distribution and faunal interaction. Implicit are changes to the active layer depth and bed porosity, both critical in describing processes such as armour layer development, surface-subsurface exchange processes and siltation/ sealing. Whilst measurements of the bed surface are increasingly informed by quantitative and spatial measurement techniques (e.g., laser displacement scanning), material opacity has precluded the full 3D bed structure analysis required to accurately define the surface-subsurface transition. To overcome this problem, this paper provides magnetic resonance imaging (MRI) data of vertical bed porosity profiles. Uniform and bimodal (?? _g = 2.1) sand-gravel beds are considered following restructuring under sub-threshold flow durations of 60 and 960 minutes. MRI data are compared to traditional 2.5D laser displacement scans and six robust definitions of the surface-subsurface transition are provided; these form the focus of discussion.     

Advancing Global Marine Biogeography Research with Open‐source GIS Software and Cloud Computing

Across many scientific domains, the ability to aggregate disparate datasets enables more meaningful global analyses. Within marine biology, the Census of Marine Life served as the catalyst for such a global data aggregation effort. Under the Census framework, the Ocean Biogeographic Information System was established to coordinate an unprecedented aggregation of global marine biogeography data. The OBIS data system now contains 31.3 million observations, freely accessible through a geospatial portal. The challenges of storing, querying, disseminating, and mapping a global data collection of this complexity and magnitude are significant. In the face of declining performance and expanding feature requests, a redevelopment of the OBIS data system was undertaken. Following an Open Source philosophy, the OBIS technology stack was rebuilt using PostgreSQL, PostGIS, GeoServer and OpenLayers. This approach has markedly improved the performance and online user experience while maintaining a standards‐compliant and interoperable framework. Due to the distributed nature of the project and increasing needs for storage, scalability and deployment flexibility, the entire hardware and software stack was built on a Cloud Computing environment. The flexibility of the platform, combined with the power of the application stack, enabled rapid re‐development of the OBIS infrastructure, and ensured complete standards‐compliance.     

Three- dimensional vector modeling and restoration of flat finite wave tank radiometric measurements

In this paper, a three-dimensional Fourier transform inversion method describing the interaction between water surface emitted radiation from a flat finite wave tank and antenna radiation characteristics is reported. The transform technique represents the scanning of the antenna mathematically as a correlation. Computation time is reduced by using the efficient and economical fast Fourier transform algorithm. To verify the inversion method, computations have been made and compared with known data and other available results. The technique has been used to restore data of the finite wave tank system and other available antenna temperature measurements made at the Cape Cod Canal. The restored brightness temperatures serve as better representations of the emitted radiation than the measured antenna temperatures.     

Apatite and scapolite as petrogenetic indicators in granolites of Milford Sound,New Zealand

A network of 5 cm wide subplanar zones of garnet-granolite with accessory apatite as the dominant hydrous mineral, is overprinted on basic hornblende-granolites in an area of present and past tectonic uplift. Fracturing and the garnet forming reactions appear to be caused by destabilisation of hornblende, as a hydrous phase, through a critical drop in the PT ratio. Whereas the apatites from the hornblende-granolite have normal compositions, apatites from the garnet-granolite zones are among the most chlorine enriched hydroxyfluorapatites known. A later amphibolite facies event has depleted hydrous minerals of fluorine and chlorine, affecting hornblende more strongly than apatite. Based on literature data on F and Cl in coexisting minerals, original hornblende compositions are tentatively restored. It is then possible to derive all the chlorine of the garnet zone apatites from the original rock, with differential loss of H₂O and HF over chlorine during the dehydration reaction. Diffusion coefficients would have been larger for H₂O and HF than for the large chloride ion, and if the gas phase was in contact with even minor anatectic melts, activity gradients would also have been relatively small for chlorine. Low-Cl scapolite is present in quartz-free pegmatoid veins. Field evidence for a genetic tie between the garnet zones and these veins is inconclusive, but liberation of H₂O and HF under granolite facies conditions is likely to have caused limited fusion of the plagioclase. Since many garnet zones do not contain even small pegmatoid veins, melts related to their formation could have collected in veins only after initial diffusion or infiltration over a distance, and without leaving segregated mafic residues.     

On the value of isotope-enabled hydrological model calibration

ABSTRACT

Calibration of hydrological models is challenging in high-latitude regions where hydrometric data are minimal. Process-based models are needed to predict future changes in water supply, yet often with high amounts of uncertainty, in part, from poor calibrations. We demonstrate the utility of stable isotopes (¹⁸O, ²H) as data employed for improving the amount and type of information available for model calibration using the isoWATFLOOD^TM model. We show that additional information added to calibration does not hurt model performance and can improve simulation of water volume. Isotope-enabled calibration improves long-term validation over traditional flow-only calibrated models and offers additional feedback on internal flowpaths and hydrological storages that can be useful for informing internal water distribution and model parameterization. The inclusion of isotope data in model calibration reduces the number of realistic parameter combinations, resulting in more constrained model parameter ranges and improved long-term simulation of large-scale water balance.     

Influence of hydropower outflow characteristics on riverbank stability: case of the lower Osage River (Missouri,USA)

ABSTRACT

This research examined the influences of outflow characteristics affecting riverbank stability. The 130-km stretch of the Lower Osage River downstream from Bagnell Dam (Missouri, USA) provided an excellent case study for this purpose. The integrated BSTEM model with the HEC-RAS model was accurately calibrated and validated with data from the US Geological Survey. Then, the outflow characteristics (peak flow duration, flow drawdown rate, and low flow duration) were investigated individually. The results of this study showed that: (1) riverbank stability is little affected by the duration time of the peak flow, especially on the reaches far from the dam; (2) sudden flow drawdown significantly reduces riverbank stability; however, the impact of the drawdown rate decreases with distance from the dam; and (3) the duration of the low flow after peak flow influences the riverbank stability value proportional to the distance from the dam. The time of low flow before failure increases as the distance from the dam increases.     

Specific surface area as a maturity index of lunar fines

Mature surface fines have an equilibrium specific surface area of about 0.6 m²/g, the equivalent mean particle size being about 3 μm. The adsorption behavior of inert gases (reversible isotherms) indicates that the particles are also non-porous in the size range of pores 10–300Å. Apparently in mature soils there is a balance in the forces which cause fining, attrition, pore filling and growth of lunar dust grains. Immature, lightly irradiated soils usually have coarser grains which reduce in size as aging proceeds. The specific surface area, determined by nitrogen or krypton sorption at 77°K, is a valuable index of soil maturity.