The northern boundary of the Jan Mayen microcontinent, North Atlantic determined from ocean bottom seismic, multichannel seismic, and gravity data   总被引：1，自引：0，他引：1  

Aleksandre Kandilarov  Rolf Mjelde  Rolf-Birger Pedersen  Bjarte Hellevang  Cord Papenberg  Carl-Joerg Petersen  Lars Planert  Ernst Flueh 《Marine Geophysical Researches》2012,33(1):55-76

The Jan Mayen microcontinent was as a result of two major North Atlantic evolutionary cornerstones—the separation of Greenland from Norway (~54 Ma), accompanied by voluminous volcanic activity, and the jump of spreading from the Aegir to the Kolbeinsey ridge (~33 Ma), which resulted in the separation of the microcontinent itself from Eastern Greenland (~24 Ma). The resulting eastern and western sides of the Jan Mayen microcontinent are respectively volcanic and non-volcanic rifted margins. Until now the northern boundary of the microcontinent was not precisely known. In order to locate this boundary, two combined refraction and reflection seismic profiles were acquired in 2006: one trending S–N and consisting of two separate segments south and north of the island of Jan Mayen respectively, and the second one trending SW–NE east of the island. Crustal P-wave velocity models were derived and constrained using gravity data collected during the same expedition. North of the West Jan Mayen Fracture Zone (WJMFZ) the models show oceanic crust that thickens from west to east. This thickening is explained by an increase in volcanic activity expressed as a bathymetric high and most likely related to the proximity of the Mohn ridge. East of the island and south of the WJMFZ, oceanic Layers 2 and 3 have normal seismic velocities but above normal average crustal thickness (~11 km). The similarity of the crustal thickness and seismic velocities to those observed on the conjugate M?re margin confirm the volcanic origin of the eastern side of the microcontinent. Thick continental crust is observed in the southern parts of both profiles. The northern boundary of the microcontinent is a continuation of the northern lineament of the East Jan Mayen Fracture Zone. It is thus located farther north than previously assumed. The crust in the middle parts of both models, around Jan Mayen island, is more enigmatic as the data suggest two possible interpretations—Icelandic type of oceanic crust or thinned and heavily intruded continental crust. We prefer the first interpretation but the latter cannot be completely ruled out. We infer that the volcanism on Jan Mayen is related to the Icelandic plume.  相似文献   

Uncertainty estimation for operational ocean forecast products—a multi-model ensemble for the North Sea and the Baltic Sea     

Inga Golbeck  Xin Li  Frank Janssen  Thorger Brüning  Jacob W. Nielsen  Vibeke Huess  Johan Söderkvist  Bjarne Büchmann  Simo-Matti Siiriä  Olga Vähä-Piikkiö  Bruce Hackett  Nils M. Kristensen  Harald Engedahl  Ed Blockley  Alistair Sellar  Priidik Lagemaa  Jose Ozer  Sebastien Legrand  Patrik Ljungemyr  Lars Axell 《Ocean Dynamics》2015,65(12):1603-1631

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Ocean eddy momentum fluxes at the latitudes of the Gulf Stream and the Kuroshio extensions as revealed by satellite data     

Richard John Greatbatch  Xiaoming Zhai  Jan-Dirk Kohlmann  Lars Czeschel 《Ocean Dynamics》2010,60(3):617-628

Eddy momentum fluxes, i.e. Reynold stresses, are computed for the latitude bands of the Gulf Stream and Kuroshio extensions using 13 years of data from the merged satellite altimeter product of Le Traon et al. The spatial pattern and amplitude of the fluxes is remarkably similar to that found by Ducet and Le Traon using the 5 years of data that were available to them. In addition to updating the work of Ducet and Le Traon, we provide new insight into the role played by the underlying variable bottom topography, both for determining the structure of the eddy momentum fluxes seen in the satellite data and for influencing the way these fluxes feedback on the mean flow. While there is no clear evidence that eddies locally flux momentum into the eastward jets of the Gulf Stream and Kuroshio extensions, a clearer picture emerges after zonally integrating across each of the North Atlantic and North Pacific basins. We argue that the eddy momentum fluxes do indeed drive significant transport, a conclusion supported by preliminary results from a 3-D model calculation. We also present evidence that in the North Pacific, the Reynolds stresses are important for driving the recirculation gyres associated with the Kuroshio extension, taking advantage of new data from both observations and high-resolution model simulations.  相似文献   

Meteorology and oceanography of the Atlantic sector of the Southern Ocean—a review of German achievements from the last decade     

Hartmut H. Hellmer  Monika Rhein  Günther Heinemann  Janna Abalichin  Wafa Abouchami  Oliver Baars  Ulrich Cubasch  Klaus Dethloff  Lars Ebner  Eberhard Fahrbach  Martin Frank  Gereon Gollan  Richard J. Greatbatch  Jens Grieger  Vladimir M. Gryanik  Micha Gryschka  Judith Hauck  Mario Hoppema  Oliver Huhn  Torsten Kanzow  Boris P. Koch  Gert König-Langlo  Ulrike Langematz  Gregor C. Leckebusch  Christof Lüpkes  Stephan Paul  Annette Rinke  Bjoern Rost  Michiel Rutgers van der Loeff  Michael Schröder  Gunther Seckmeyer  Torben Stichel  Volker Strass  Ralph Timmermann  Scarlett Trimborn  Uwe Ulbrich  Celia Venchiarutti  Ulrike Wacker  Sascha Willmes  Dieter Wolf-Gladrow 《Ocean Dynamics》2016,66(11):1379-1413

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The Major Soils of a Village in Northern Burkina Faso     

Lars Krogh M.Sc. 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):90-100

Krogh, Lars: The Major Soils of a Village in Northern Burkina Faso. Geografisk Tidsskrift 93:90–100. Copenhagen 1993.

In the Oudalan Province of Sahelian Northern Burkina Faso soil investigations have been carried out in order to evaluate the sustainability of millet production with emphasis on the dynamics of soil fertility. Some results of pedological investigations carried out in 1990 are included. Three commonly occurring soil types in a village territory are examined and their genesis and fertility discussed. Analyses show that the soils are inherently low in organic matter. The level of macro-nutrients is low, soil structure is weak or unfavourable: all probably due to a combination of natural and human factors. Crop yields are generally low and cannot be raised without more intensive cultivation.  相似文献   

Rapid generation of Digital Elevation Models from topographic maps     

Lars Eklundh  Ulrik Mårtensson 《International journal of geographical information science》2013,27(3):329-340

Abstract

In this article we demonstrate that substantial gains in time can be made when using point sampling rather than contour line digitising for generation of Digital Elevation Models (DEMs). A simple sampling scheme, based on regularly distributed points, was used supplemented with points near break-lines in the terrain. An evaluation of surfaces created with three different interpolation methods at three different resolutions shows that the statistical distribution was better when using points as opposed to contours, and that the accuracy was comparable despite the much smaller amount of input data.  相似文献   

Effects of CO₂ on benthic biota: An in situ benthic chamber experiment in Storfjorden (Norway)     

Hiroshi Ishida  Lars G. Golmen  Julia West  Martin Krüger  Patricia Coombs  John Arthur Berge  Tastuo Fukuhara  Michimasa Magi  Jun Kita 《Marine pollution bulletin》2013

Carbon capture and storage (CCS) methods, either sub-seabed or in ocean depths, introduces risk of CO₂ leakage and subsequent interaction with the ecosystem. It is therefore important to obtain information on possible effects of CO₂. In situ CO₂ exposure experiments were carried out twice for 10 days during 2005 using a Benthic Chamber system at 400 m depth in Storfjorden, Norway. pCO₂ in the water above the sediment in the chambers was controlled at approximately 500, 5000 and 20,000 μatm, respectively. This article describes the experiment and the results from measured the biological responses within the chamber sediments. The results show effects of elevated CO₂ concentrations on biological processes such as increased nanobenthos density. Methane production and sulphate reduction was enhanced in the approximately 5000 μatm chamber.  相似文献   

Determination of gravity anomaly at sea level from inversion of satellite gravity gradiometric data   总被引：1，自引：0，他引：1  

Mehdi Eshagh  Lars E. Sjberg 《Journal of Geodynamics》2011,51(5):366-377

Gravity gradients can be used to determine the local gravity field of the Earth. This paper investigates downward continuation of all elements of the disturbing gravitational tensor at satellite level using the second-order partial derivatives of the extended Stokes formula in the local-north oriented frame to determine the gravity anomaly at sea level. It considers the inversion of each gradient separately as well as their joint inversion. Numerical studies show that the gradients T_zz, T_xx, T_yy and T_xz have similar capability of being continued downward to sea level in the presence of white noise, while the gradient T_yz is considerably worse than the others. The bias-corrected joint inversion process shows the possibility of recovering the gravity anomaly with 1 mGal accuracy. Variance component estimation is also tested to update the observation weights in the joint inversion.  相似文献   

淮河流域水文随机方法的径流图化(英文)     

严子奇  夏军 《地理学报(英文版)》2011,21(3):441-457

Theoretical difficulties for mapping and for estimating river regime characteristics in a large-scale basin remain because of the nature of the variable under study: river flows are related to a specific area, i.e. the drainage basin, and are hierarchically organized in space through the river network with upstream-downstream dependencies. Another limitation is there are not enough gauge stations in developing countries. This presentation aims at de-veloping the hydro-stochastic approach for producing choropleth maps of average annual runoff and computing mean discharge along the main river network for a large-scale basin. The approach applied to mean annual runoff is based on geostatistical interpolation proce-dures coupled with water balance and data uncertainty analyses. It is proved by an applica-tion in the upstream at Bengbu in the Huaihe River Basin, a typical large-scale basin in China. Hydro-stochasitic approach in a first step interpolates to a regular grid net and in a second step the grid values are integrated along rivers. The interpolation scheme includes a con-straint to be able to account for the lateral water balance along the rivers. Grid runoff map with 10 km × 10 km resolution and the discharge map along the river with the 1 km basic length unit are the main results in this study. This kind of statistic approach can be widely used be-cause it avoids the complexity of hydrological models and does not depend on the meteoro-logical data.  相似文献   

The use of spectral analysis-based exact solutions to characterize topography-controlled groundwater flow   总被引：2，自引：1，他引：1  

Lars Marklund  Anders W?rman 《Hydrogeology Journal》2011,19(8):1531-1543

Spectral analysis enhances the ability to analyze groundwater flow at a steady state by separating the top boundary condition into its periodic forms. Specifically, spectral analysis enables comparisons of the impact of individual spatial scales on the total flow field. New exact spectral solutions are presented for analyzing 3D groundwater flow with an arbitrarily shaped top boundary. These solutions account for depth-decaying, anisotropic and layered permeability while utilizing groundwater flux or the phreatic surface as a top boundary condition. Under certain conditions, groundwater flow is controlled by topography. In areas where the groundwater flow is controlled by the topography, the unknown water table is often approximated by the topography. This approximation induces a systematic error. Here, the optimal resolution of digital elevation models (DEMs) is assessed for use as a top boundary in groundwater flow models. According to the analysis, the water-table undulation is smoother than the topography; therefore, there is an upper limit to the resolution of DEMs that should be used to represent the groundwater surface. The ability to represent DEMs of various spectral solutions was compared and the results indicate that the fit is strongly dependent on the number of harmonics in the spectral solution.  相似文献