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21.
While current rates of sea level rise and associated coastal flooding in the New York City region appear to be manageable by stakeholders responsible for communications, energy, transportation, and water infrastructure, projections for sea level rise and associated flooding in the future, especially those associated with rapid icemelt of the Greenland and West Antarctic Icesheets, may be outside the range of current capacity because extreme events might cause flooding beyond today??s planning and preparedness regimes. This paper describes the comprehensive process, approach, and tools for adaptation developed by the New York City Panel on Climate Change (NPCC) in conjunction with the region??s stakeholders who manage its critical infrastructure, much of which lies near the coast. It presents the adaptation framework and the sea-level rise and storm projections related to coastal risks developed through the stakeholder process. Climate change adaptation planning in New York City is characterized by a multi-jurisdictional stakeholder?Cscientist process, state-of-the-art scientific projections and mapping, and development of adaptation strategies based on a risk-management approach.  相似文献   
22.
23.
The largest error in determining volcanic gas fluxes using ground based optical remote sensing instruments is typically the determination of the plume speed, and in the case of fixed scanning instruments also the plume height. We here present a newly developed technique capable of measuring plume height, plume speed and gas flux using one single instrument by simultaneously collecting scattered sunlight in two directions. The angle between the two measurement directions is fixed, removing the need for time consuming in-field calibrations. The plume height and gas flux is measured by traversing the plume and the plume speed is measured by performing a stationary measurement underneath the plume. The instrument was tested in a field campaign in May 2005 at Mt. Etna, Italy, where the measured results are compared to wind fields derived from a meso-scale meteorological model (MM5). The test and comparison show that the instrument is functioning and capable of estimating wind speed at the plume height.  相似文献   
24.
Regional ground water flow is most usually estimated using Darcy's law, with hydraulic conductivities estimated from pumping tests, but can also be estimated using ground water residence times derived from radioactive tracers. The two methods agree reasonably well in relatively homogeneous aquifers but it is not clear which is likely to produce more reliable estimates of ground water flow rates in heterogeneous systems. The aim of this paper is to compare bias and uncertainty of tracer and hydraulic approaches to assess ground water flow in heterogeneous aquifers. Synthetic two-dimensional aquifers with different levels of heterogeneity (correlation lengths, variances) are used to simulate ground water flow, pumping tests, and transport of radioactive tracers. Results show that bias and uncertainty of flow rates increase with the variance of the hydraulic conductivity for both methods. The bias resulting from the nonlinearity of the concentration–time relationship can be reduced by choosing a tracer with a decay rate similar to the mean ground water residence time. The bias on flow rates estimated from pumping tests is reduced when performing long duration tests. The uncertainty on ground water flow is minimized when the sampling volume is large compared to the correlation length. For tracers, the uncertainty is related to the ratio of correlation length to the distance between sampling wells. For pumping tests, it is related to the ratio of correlation length to the pumping test's radius of influence. In regional systems, it may be easier to minimize this ratio for tracers than for pumping tests.  相似文献   
25.
We present a numerical study for 3D time‐lapse electromagnetic monitoring of a fictitious CO2 sequestration using the geometry of a real geological site and a suite of suitable electromagnetic methods with different source/receiver configurations and different sensitivity patterns. All available geological information is processed and directly implemented into the computational domain, which is discretized by unstructured tetrahedral grids. We thus demonstrate the performance capability of our numerical simulation techniques. The scenario considers a CO2 injection in approximately 1100 m depth. The expected changes in conductivity were inferred from preceding laboratory measurements. A resistive anomaly is caused within the conductive brines of the undisturbed reservoir horizon. The resistive nature of the anomaly is enhanced by the CO2 dissolution regime, which prevails in the high‐salinity environment. Due to the physicochemical properties of CO2, the affected portion of the subsurface is laterally widespread but very thin. We combine controlled‐source electromagnetics, borehole transient electromagnetics, and the direct‐current resistivity method to perform a virtual experiment with the aim of scrutinizing a set of source/receiver configurations with respect to coverage, resolution, and detectability of the anomalous CO2 plume prior to the field survey. Our simulation studies are carried out using the 3D codes developed in our working group. They are all based on linear and higher order Lagrange and Nédélec finite‐element formulations on unstructured grids, providing the necessary flexibility with respect to the complex real‐world geometry. We provide different strategies for addressing the accuracy of numerical simulations in the case of arbitrary structures. The presented computations demonstrate the expected great advantage of positioning transmitters or receivers close to the target. For direct‐current geoelectrics, 50% change in electric potential may be detected even at the Earth's surface. Monitoring with inductive methods is also promising. For a well‐positioned surface transmitter, more than 10% difference in the vertical electric field is predicted for a receiver located 200 m above the target. Our borehole transient electromagnetics results demonstrate that traditional transient electromagnetics with a vertical magnetic dipole source is not well suited for monitoring a thin horizontal resistive target. This is due to the mainly horizontal current system, which is induced by a vertical magnetic dipole.  相似文献   
26.
We present a high-resolution dark matter reconstruction of the   z = 0.165  Abell 901/902 supercluster from a weak lensing analysis of the Hubble Space Telescope STAGES survey. We detect the four main structures of the supercluster at high significance, resolving substructure within and between the clusters. We find that the distribution of dark matter is well traced by the cluster galaxies, with the brightest cluster galaxies marking out the strongest peaks in the dark matter distribution. We also find a significant extension of the dark matter distribution of Abell 901a in the direction of an infalling X-ray group Abell 901α. We present mass, mass-to-light and mass-to-stellar mass ratio measurements of the structures and substructures that we detect. We find no evidence for variation of the mass-to-light and mass-to-stellar mass ratio between the different clusters. We compare our space-based lensing analysis with an earlier ground-based lensing analysis of the supercluster to demonstrate the importance of space-based imaging for future weak lensing dark matter 'observations'.  相似文献   
27.
Simulated circum-Arctic climate changes by the end of the 21st century   总被引:1,自引:0,他引:1  
This study investigates future changes of the Arctic climate by the end of the 21st century, simulated by the regional climate model HIRHAM forced with the ECHAM5/MPI-OM general circulation model and assuming the SRES A1B emission scenario. This assessment provides the regional patterns of future circulation, temperature, and precipitation in the Arctic by the end of the 21st century. The magnitude of winter and summer temperature and precipitation is projected to increase, while their interannual variability is projected to change seasonally and is regionally dependent. The regional-scale response of the temperature and precipitation is associated with changes in storm tracks and atmospheric baroclinicity. During winter, the regions of strongest baroclinicity are shifted northward and strengthened. Changes in the seasonal temperature and precipitation are accompanied by changes in their extremes. Extreme warm and cold events are significantly projected to change, with relative changes of seasonal precipitation being larger than those of precipitation extremes.  相似文献   
28.
This GGR biennial critical review covers developments and innovations in key analytical methods published since January 2014, relevant to the chemical, isotopic and crystallographic characterisation of geological and environmental materials. In nine selected analytical fields, publications considered to be of wide significance are summarised, background information is provided and their importance evaluated. In addition to instrumental technologies, this review also presents a summary of new developments in the preparation and characterisation of rock, microanalytical and isotopic reference materials, including a précis of recent changes and revisions to ISO guidelines for reference material characterisation and reporting. Selected reports are provided of isotope ratio determinations by both solution nebulisation MC‐ICP‐MS and laser ablation‐ICP‐MS, as well as of radioactive isotope geochronology by LA‐ICP‐MS. Most of the analytical techniques elaborated continue to provide new applications for geochemical analysis; however, it is noted that instrumental neutron activation analysis has become less popular in recent years, mostly due to the reduced availability of nuclear reactors to act as a neutron source. Many of the newer applications reported here provide analysis at increasingly finer resolution. Examples include atom probe tomography, a very sensitive method providing atomic scale information, nanoscale SIMS, for isotopic imaging of geological and biological samples, and micro‐XRF, which has a spatial resolution many orders of magnitude smaller than conventional XRF.  相似文献   
29.
A potential zircon reference material (BB zircon) for laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) U‐Pb geochronology and Hf isotope geochemistry is described. A batch of twenty zircon megacrysts (0.5–1.5 cm3) from Sri Lanka was studied. Within‐grain rare earth element (REE) compositions are largely homogeneous, albeit with some variation seen between fractured and homogeneous domains. Excluding fractured cathodoluminescence bright domains, the variation in U content for all analysed crystals ranged from 227 to 368 μg g?1 and the average Th/U ratios were between 0.20 and 0.47. The Hf isotope composition (0.56–0.84 g/100 g Hf) is homogeneous within and between the grains – mean 176Hf/177Hf of 0.281674 ± 0.000018 (2s). The calculated alpha dose of 0.59 × 1018 g?1 for a number of BB grains falls within the trend of previously studied, untreated zircon samples from Sri Lanka. Aliquots of the same crystal (analysed by ID‐TIMS in four different laboratories) gave consistent U‐Pb ages with excellent measurement reproducibility (0.1–0.4% RSD). Interlaboratory assessment (by LA‐ICP‐MS) from individual crystals returned results that are within uncertainty equivalent to the TIMS ages. Finally, we report on within‐ and between‐grain homogeneity of the oxygen isotope systematic of four BB crystals (13.16‰ VSMOW).  相似文献   
30.
We apply a coupled thermomechanical ice sheet—self-gravitating viscoelastic solid Earth model (SGVEM), allowing for the dynamic exchange of ice thickness and bedrock deformation, in order to investigate the effect of viscoelastic deformation on ice dynamics and vice versa. In a synthetic glaciation scenario, we investigate the interaction between the ice sheet and the solid Earth deformation, the glacial-isostatic adjustment (GIA), accounting for an atmospheric forcing depending on the ice sheet surface altitude. We compare the results from the coupled model to runs with the common elastic lithosphere/relaxing asthenosphere (ELRA) model, where the lithosphere is represented by a thin plate and the mantle relaxes with one characteristic relaxation time, as well as to a rigid Earth without any deformation. We find that the deformational behaviour of the SGVEM on ice dynamics (i.e. stored ice volume, ice thickness and velocity field) is comparable to the ELRA for an optimal choice of the parameters in steady state, but exhibits differences in the transient behaviour. Beyond the ice sheet, in the region of peripheral forebulge, the differences in the transient surface deformation between ELRA and SGVEM are substantial, demonstrating the inadequacy of the ELRA model for interpreting constraints on GIA in the periphery of the ice sheet, such as sea-level indicators and GPS uplift rates.  相似文献   
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