Features and spatial distribution of circumpolar deep water in the southern Indian Ocean and the effects of Antarctic circum polar current     

蒲书箴  董兆乾  于卫东  卢燕  项宝强 《极地研究(英文版)》2007,18(2):100-109

The data from the Southern Ocean observations of World Ocean Circulation Experiment(WOCE) are used for analysis and illustration of the features and spatial distributions of Circumpolar Deep Water(CDW) in the southern Indian Ocean.It is learnt from the comparison among the vertical distributions of temperature/salinity/oxygen along the 30°E,90°E and 145°E sections respectively that some different features of CDW and the fronts can be found at those longitudes,and those differences can be attributed to the zonal transoceanic flow and the merizonal movement in the Circumpolar Deep Water.In fact,the zonal transoceanic flow is the main dynamic factor for the water exchange between the Pacific Ocean and the Indian Ocean or between the Atlantic Ocean and the Indian Ocean,and for the effects on the spatial distributions of the physical properties in CDW.  相似文献   

Wavefield decomposition for passive ocean bottom seismological data   总被引：1，自引：0，他引：1  

M. Thorwart  T. Dahm 《Geophysical Journal International》2005,163(2):611-621

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II. Snow hydrology processes and remote sensing     

Albert Rango 《水文研究》1993,7(2):121-138

In the last 20 years remote sensing research has led to significant progress in monitoring and measuring certain snow hydrology processes. Snow distribution in a drainage basin can be adequately assessed by visible sensors. Although there are still some interpretation problems, the NOAA-AVHRR sensor can provide frequent views of the areal snow cover in a basin, and snow cover maps are produced operationally by the National Weather Service on about 3000 drainage basins in North America. Measurement of snow accumulation or snow water equivalent with microwave remote sensing has great potential because of the capabilities for depth penetration, all-weather observation and night-time viewing. Several critical areas of research remain, namely, the acquisition of snow grain size information for input to microwave models and improvement in passive microwave resolution from space. Methods that combine both airborne gamma ray and visible satellite remote sensing of the snowpack with field measurements also hold promise for determining areal snow water equivalent. Some remote sensing techniques can also be used to detect different stages of snow metamorphism. Various aspects of snowpack ripening can be detected using microwave and thermal infra-red capabilities. The capabilities for measurement of snow albedo and surface temperature have direct application in both snow metamorphism and snowpack energy balance studies. The potentially most profitable research area here is the study of the bidirectional reflectance distribution function to improve snow albedo measurements. Most of the remote sensing capabilities in snow hydrology have been developed for improving snowmelt-run-off forecasting. Most applications have used the input of snow cover extent to deterministic models, both of the degree day and energy balance types. Snowmelt-run-off forecasts using satellite derived snow cover depletion curves and the models have been successfully made. As the extraction of additional snow cover characteristics becomes possible, remote sensing will have an even greater impact on snow hydrology. Important remote sensing capabilities will become available in the next 20 years through space platform observing systems that will improve our capability to observe the snowpack on an operational basis.  相似文献   

The fit of polar wander curves by small circles using Marquardt's algorithm: statistical properties     

J. J. Schott  J. C. Turlot  J. Thomann 《Geophysical Journal International》1991,105(3):731-745

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On the winter evolution of snow thermophysical properties over land‐fast first‐year sea ice     

Alexandre Langlois  C. J. Mundy  David G. Barber 《水文研究》2007,21(6):705-716

The geophysical, thermodynamic and dielectric properties of snow are important state variables that are known to be sensitive to Arctic climate variability and change. Given recent observations of changes in the Arctic physical system (Arctic Climate Impact Assessment, 2004), it is important to focus on the processes that give rise to variability in the horizontal, vertical and temporal dimensions of the life‐history of snow on sea ice. The objectives in this study are to present these ‘state’ variables and to investigate the processes that govern variability in the vertical, horizontal and temporal dimension by using a case study over land‐fast first‐year sea ice for the period December 2003 to June 2004. Results from two sampling areas (thin and thick snowpacks) show that differences in snowpack thickness can substantially change the vertical and temporal evolution of snow properties. During the late fall and early winter (cooling period) we measured no significant changes in the physical properties, except for thin snow‐cover salinity, which decreased throughout the period. Fall‐snow desalination was only observed under thin snowpacks with a rate of ?0·12 ppt day^?1. Significant changes occurred in the late winter and early spring (warming period), especially for snow grain size. Snow grain kinetic growth of 0·25–0·48 mm·day^?1 was measured coincidently with increasing salinity and wetness for both thin and thick snowpacks. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Laboratory Research into Permeable Reactive Barriers for Groundwater Remediation   总被引：2，自引：0，他引：2  

Anthony Adzomani  Jun Dong  Yan Jin 《东北亚地学研究》2003,(1)

1IntroductionAs industrialization is gaining roots throughout the world and population is increasing, there is the accompanying problem of waste disposal from vari-ous sources. Due to inefficient waste management processes, subsurface water bodies are being con-taminated by various kinds of chemicals (Soliman etal., 1998). PRB is a comparatively new groundwater treat-ment technology where contaminants are converted into harmless by products in situ as the polluted water passes through a re…  相似文献   

Numerical slope stability simulations of the northern wall of eastern Candor Chasma (Mars) utilizing a distinct element method     

B. Imre 《Planetary and Space Science》2004,52(14):1303-1319

Valles Marineris offers a deep natural insight into the upper crust of Mars. The morphology of its slopes reflects the properties of the wall materials, thus constraining in models of composition and evolution of the upper layers of the Martian crust. Hence, knowledge about the lithological composition of these wall rocks is of major interest to the understanding of the geological and climatic history of Mars. This study investigates mechanical rock mass parameters of the northern wall of eastern Candor Chasma (between 290°E and 296°E longitude, −8° to −5° latitude). These are inferred from its present-day morphology and a proposed slope-forming history, applying a distinct element code to simulate the stability and the tectonic history of this slope within a parameter study. Additionally, a mathematical denudation model is applied to take into account the effect of exogenic processes on the slope. The study results show that two periods of normal faulting in conjunction with massive interim denudational scarp recess is a valid model for the evolution of the northern wall of eastern Candor Chasma. The estimated rate of scarp recess of 60 m Myr⁻¹ is comparable with certain terrestrial scarp retreat rates. The best-fit models yield a homogenous distribution of low-level rock mass strength and deformability properties distributed over the entire stratigraphic column of the northern wall of eastern Candor Chasma. The values are 5.0 (±0.7) MPa for the uniaxial compressive strength, 1.6 (±0.2) MPa for the Brazilian tensile strength, 4.7 (±1.5) GPa for the Young's modulus, 0.2 (±0.15) for the Poisson's ratio, 22 (±2)° for the internal friction angle, 1.6 (±0.2) MPa for the cohesion and 2200 (±500) kg m⁻³ for the density. This study favors columnar jointed basalt as the material that builds up the northern wall of eastern Candor Chasma and other walls within central Valles Marineris. The best-fit denudational model of the upper slope section of the northern wall of eastern Candor Chasma indicates a distinct cap rock unit of lesser susceptibility to denudation than the wall rock below.  相似文献   

Patterns of soil temperature and moisture in the active layer and upper permafrost at Barrow, Alaska: 1993–1999     

K. M. Hinkel  F. Paetzold  F. E. Nelson  J. G. Bockheim   《Global and Planetary Change》2001,29(3-4)

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Effects and mechanism of igneous rock on selenium in the tropical soil-rice system in Hainan Province,South China     

Xiu-jin Liu  Ke Yang  Fei Guo  Shi-qi Tang  Ying-han Liu  Li Zhang  Hang-xin Cheng  Fei Liu 《China Geology》2022,5(1):1-11

To illuminate the migration and transformation of selenium(Se)in the igneous rock-soil-rice system,285 pairs of rhizosphere soil and rice samples were collected from the granitoid and basalt areas in Hainan Province,South China.The contents of Se in soils derived from granitoid and basalt are,respectively,0.19±0.12 mg/kg and 0.34±0.39 mg/kg,which are much higher than Se contents in granitoid and basalt.Selenium shows remarkable enrichment from granitoid and basalt to soils.The mobile fraction of Se in soils derived from granitoid is 0.0100±0.0034 mg/kg,which is significantly higher than that of basalt(0.0058±0.0039 mg/kg).Although soil derived from basalt shows higher Se contents,Se contents in rice samples,mobile fractions of Se in soils,and biological concentration factor(BCF)is similar or even lower than that from granitoid.Basalt consist of calcic plagioclase and pyroxene,and are much richer in Fe,Al,and Ca than granitoid.Correspondingly,the basalt-derived soils have higher goethite,hematite,kaolinite,cation exchange capacity(CEC)content,and higher p H than the granitoid-derived soils,which result in higher adsorption capacity for Se and relatively lower Se bioavailability.Soils derived from granitoid and basalt in tropical regions are beneficial to produce Se-rich rice.  相似文献   

Resistance of salt marsh substrates to near-instantaneous hydrodynamic forcing     

Helen Brooks  Iris Möller  Simon Carr  Clementine Chirol  Elizabeth Christie  Ben Evans  Kate L. Spencer  Tom Spencer  Katherine Royse 《地球表面变化过程与地形》2021,46(1):67-88

Salt marshes deliver vital ecosystem services by providing habitats, storing pollutants and atmospheric carbon, and reducing flood and erosion risk in the coastal hinterland. Net losses in salt marsh areas, both modelled globally and measured regionally, are therefore of concern. Amongst other controls, the persistence of salt marshes in any one location depends on the ability of their substrates to resist hydrodynamic forcing at the marsh front, along creek margins and on the vegetated surface. Where relative sea level is rising, marsh elevation must keep pace with sea-level rise and landward expansion may be required to compensate for areal loss at exposed margins. This paper reviews current understanding of marsh substrate resistance to the near-instantaneous (seconds to hours) forcing induced by hydrodynamic processes. It outlines how variability in substrate properties may affect marsh substrate stability, explores current understanding of the interactions between substrate properties and erosion processes, and how the cumulative impact of these interactions may affect marsh stability over annual to decadal timescales. Whilst important advances have been made in understanding how specific soil properties affect near-instantaneous marsh substrate stability, less is known about how these properties interact and alter bulk substrate resistance to hydrodynamic forcing. Future research requires a more systematic approach to quantifying biological and sedimentological marsh substrate properties. These properties must then be linked to specific observable erosion processes, particularly at the marsh front and along creek banks. A better understanding of the intrinsic dynamics and processes acting on, and within, salt marsh substrates will facilitate improved prediction of marsh evolution under future hydrodynamic forcing scenarios. Notwithstanding the additional complications that arise from morphodynamic feedbacks, this would allow us to more accurately model the future potential protection from flooding and erosion afforded by marshes, while also increasing the effectiveness of salt marsh restoration and recreation schemes. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献