The cyclonic circulation in the Australian–Antarctic basin simulated by an eddy-resolving general circulation model     

Shigeru Aoki  Yoshikazu Sasai  Hideharu Sasaki  Humio Mitsudera  Guy D. Williams 《Ocean Dynamics》2010,60(3):743-757

Flow structure in the Australian–Antarctic basin is investigated using an eddy-resolving general ocean circulation model and validated with iceberg and middepth float trajectories. A cyclonic circulation system between the Antarctic Circumpolar Current and Antarctic Slope Current consists of a large-scale gyre in the west (80–110° E) and a series of eddies in the east (120–150° E). The western gyre has an annual mean westward transport of 22 Sv in the southern limb. Extending west through the Princess Elizabeth Trough, 5 Sv of the gyre recirculates off Prydz Bay and joins the western boundary current off the Kerguelen Plateau. Iceberg trajectories from QuickScat and ERS-1/2 support this recirculation and the overall structure of the Antarctic Slope Current against isobath in the model. Argo float trajectories also reveal a consistent structure of the deep westward slope current. This study indicates the presence of a large cyclonic circulation in this basin, which is comparable to the Weddell and Ross gyres.  相似文献   

Relationships between water flow rate and geophysical measurements in an alluvial aquifer     

Pascale Sénéchal  Guy Sénéchal 《Acta Geophysica》2010,58(1):83-95

Our study focuses on the potential usefulness of surface geophysical data to constrain the water content within an alluvial aquifer. On a study area where two wells have been drilled, we have performed several geophysical measurements, including ground penetrating radar, DC resistivity prospecting, seismic refraction survey and magnetic resonance soundings. From these data, we estimated several parameters, namely, the water height in the deposits, the effective porosity, the water content, the permeability, and the transmissivity of alluvial deposits. These physical parameters allow us to characterize the alluvial deposits in order to constrain the estimation of the potential water flow. The lithology and water flow rate known from the wells enabled us to compare geophysical results obtained in a high water flow rate zone to those in a low water flow rate zone. Correlation has been found between the water flow rate observed in both wells and the geophysical data obtained in the vicinity of these wells.  相似文献   

Canonical orbital elements in terms of an arbitrary independent variable     

Victor R. Bond  Guy Janin 《Celestial Mechanics and Dynamical Astronomy》1981,23(2):159-172

Within the framework of the Hamiltonian mechanics in the extended phase space, a set of canonical elements of the Delaunay type is developed in terms of an arbitrary independent angular variable. Application to the four classical anomalies-eccentric, true, elliptic, and mean-is presented. Particular attention is given to the generalized time equation and its conjugate energy equation.  相似文献   

AGRICULTURAL INNOVATION: THE EXAMPLE OF PEANUT-GROWING IN THE BELIZE VALLEY, CENTRAL AMERICA     

Guy M. Robinson  D.Phil. 《Singapore journal of tropical geography》1985,6(2):116-126

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Ultramafic rocks of the Widgiemooltha-Norseman area,Western Australia: Petrological diversity,geochemistry and mineralisation     

G. Willett  E. Eshuys  B. Guy 《Precambrian Research》1978,6(2):133-156

Mineral exploration of the Widgiemooltha-Norseman region of Western Australia has located massive and disseminated nickel sulphide mineralisation.This paper discusses the geological setting of the nickel sulphide mineralisation with reference to the stratigraphy, structure and metamorphism of the ultramafic sequence and spatially associated rocks. The amphibolite facies metamorphosed ultramafic rocks of the Widgiemooltha area are compared with greenschist metamorphosed ultramafic rocks at Eundynie, which exhibit excellently preserved pseudomorphs of primary igneous textures.Some 2000 ultramafic rock samples were analysed for 13 element/oxides and divided into four major mineralogically and texturally distinct groups. The data were analysed statistically by determination of means and standard deviations and multiple regression analyses.The data suggest differentiation of a magma at depth followed by a vast outpouring of lava to produce picritic-peridotitic rocks. The flows crystallised with upper spinifex zones and lower euhedral-olivine zones in varying proportions dependent on magma composition. The development of spinifex texture is compositionally controlled. This texture is not developed in rocks with MgO contents greater than 26% (± 2%).The comparison of the ultramafics of the Widgiemooltha and Eundynie areas indicates that talc-carbonate formation and serpentinization have modified primary igneous textures and geochemistries, resulting in the production of a diverse group of rock types. Such post-magmatic alteration processes in association with structural elements are considered important in the upgrading of nickel sulphide mineralisation.  相似文献   

Growing mountain ranges and quenched river networks     

Sbastien Castelltort  Guy Simpson 《Comptes Rendus Geoscience》2006,338(16):1184-1193

River networks in mountain ranges owe their existence to the competing effects of tectonic uplift and climate-controlled erosion. However, paradoxically, the universal geometric properties of river networks are independent of both tectonics and climate. Currently, this paradox has still not been resolved. Here we propose a solution that consists in considering that the geometry of river networks is established on the lowland margins of incipient uplifts, and is quenched into the erosion zone as the mountain belts widen with time. In our model, the geometry of river networks simply reflects the downward coalescence of alluvial rivers on un-dissected surfaces outside of mountain belts, and is therefore independent of erosion processes. To cite this article: S. Castelltort, G. Simpson, C. R. Geoscience 338 (2006).  相似文献   

Ontario’s Environmental Farm Plan: Evaluation and research agenda     

Guy M. Robinson 《Geoforum》2006,37(5):859-873

This paper analyses the operation of the Environmental Farm Plan (EFP) scheme in Ontario, Canada, a voluntary agri-environment scheme established in 1993. Previously unpublished data and interviews with farmers, leaders of farmers’ organisations and government officials are used to detail participation rates, geographical spread and method of operation. Largely developed by farmers’ organisations, the scheme has focused on soil management, water quality and storage/disposal of agricultural wastes. The environmental actions associated with these activities are discussed, revealing both successes and limitations. Distinctions are drawn with agri-environmental schemes in the European Union, and a broader context for the EFP is provided with respect to the proposed post-productivist transition of agri-food systems and the need to examine the way these systems are regulated. A need for further systematic research is proposed, specifically with respect to barriers to participation, the voluntary nature of the scheme, financial incentives and the resultant environmental impacts.  相似文献   

What we know about elemental bulk chondrule and matrix compositions: Presenting the ChondriteDB Database     

Dominik C. Hezel  Markus Harak  Guy Libourel 《Chemie der Erde / Geochemistry》2018,78(1):1-14

Chondrules and matrix are the major components of chondritic meteorites and represent a significant evolutionary step in planet formation. The formation and evolution of chondrules and matrix and, in particular, the mechanics of chondrule formation remain the biggest unsolved challenge in meteoritics. A large number of studies of these major components not only helped to understand these in ever greater detail, but also produced a remarkably large body of data. Studying all available data has become known as ?big data? analyses and promises deep insights – in this case – to chondrule and matrix formation and relationships. Looking at all data may also allow one to better understand the mechanism of chondrule formation or, equally important, what information we might be missing to identify this process. A database of all available chondrule and matrix data further provides an overview and quick visualisation, which will not only help to solve actual problems, but also enable students and future researchers to quickly access and understand all we know about these components. We collected all available data on elemental bulk chondrule and matrix compositions in a database that we call ChondriteDB. The database also contains petrographic and petrologic information on chondrules. Currently, ChondriteDB contains about 2388 chondrule and 1064 matrix data from 70 different publications and 161 different chondrites. Future iterations of ChondriteDB will include isotope data and information on other chondrite components. Data quality is of critical importance. However, as we discuss, quality is not an objective category, but a subjective judgement. Quantifiable data acquisition categories are required that allow selecting the appropriate data from a database in the context of a given research problem. We provide a comprehensive overview on the contents of ChondriteDB. The database is available as an Excel file upon request from the senior author of this paper, or can be accessed through MetBase.  相似文献   

1995—2015年中国人口迁移的时空变化特征   总被引：2，自引：2，他引：0  

柯文前  朱宇  陈晨  Guy J.Abel  林李月  林洁 《地理学报》2022,77(2):411-425

本文利用人口普查数据,估算了1995—2015年中国地（市）间人口O-D迁移流和迁移率,结合GIS空间分析和社会网络分析方法,揭示了20年间中国人口迁移的时空变化特征。研究发现：① 中国人口迁移由相对不活跃、局部地区参与的“低活性时代”,逐步走向相对活跃、绝大多数地区参与的“高活性时代”。② 人口迁移地域类型的时空演化过程呈现出各活跃型地（市）不断扩散,而非活跃型地（市）大幅缩减的特点。③ 人口迁移网络以“胡焕庸线”为界,东、西两侧迁移流“东密西疏”且差异悬殊,这一空间格局具有很强的稳定性和顽健性。④ 在人口省内迁移持续增强,以及跨省迁移中沿海三大城市群吸引力的“此消彼长”和西南地区吸引力不断增强的背景下,东中西部地区的人口迁移流场结构表现为：沿海地区主要城市群内部分化和影响范围减弱,中部地区（除湖北省）未能演化出以省为单元的独立社区,西部地区则是西北相对稳定而西南持续变动。  相似文献   

Lagrangian sources of frontogenesis in the equatorial Atlantic front     

Hervé Giordani  Guy Caniaux 《Climate Dynamics》2014,43(11):3147-3162

Estimating the processes that control the north equatorial sea surface temperature (SST)-front on the northern edge of the cold tongue in the tropical Atlantic is a key issue for understanding the dynamics of the oceanic equatorial Atlantic and the West African Monsoon. Diagnosis of the frontogenetic forcings on a realistic high-resolution simulation was used to identify the processes involved in the formation and evolution of the equatorial SST-front. The turbulent forcing associated with the mixed-layer turbulent heat flux was found to be systematically frontolytic while the dynamic forcing associated with currents was found to be frontogenetic for the equatorial SST-front. Nevertheless, the low-frequency component of the turbulent forcing was frontogenetic and initiated the SST-front which was then amplified and maintained by the leading dynamic forcing. This forcing was mainly driven by the meridional convergence of the northern South Equatorial Current (nSEC) and the Guinea Current, which points out the essential role played by the circulation in the equatorial SST-front evolution. The quasi-biweekly variability of the equatorial SST-front and its forcings were found to be more strongly coupled to the wind energy flux (WEF) than to the surface wind stress. In fact the WEF controlled the convergence/divergence of the nSEC and Guinea Current and thus the meridional component of the leading dynamic forcing. The WEF explains the equatorial SST-front development better than the wind does because it is a coupled ocean-atmosphere process.  相似文献