Managing marine genetic diversity: time for action?   总被引：1，自引：0，他引：1  

Kenchington  Ellen; Heino  Mikko; Nielsen  Einar Eg 《ICES Journal of Marine Science》2003,60(6):1172-1176

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An ecosystem modeling approach to predicting cod recruitment     

Einar Svendsen  Morten Skogen  Paul Budgell  Geir Huse  Jan Erik Stiansen  Bjrn dlandsvik  Frode Vikeb  Lars Asplin  Svein Sundby 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2810

The Norwegian Ecological Model (NORWECOM) biophysical model system implemented with the ROMS ocean circulation model has been run to simulate conditions over the last 25 years for the North Atlantic. Modeled time series of water volume fluxes, primary production, and drift of cod larvae through their modeled ambient temperature fields have been analyzed in conjunction with VPA estimated time series of 3-year-old cod recruits in the Barents Sea. Individual time series account for less than 50% of the recruitment variability; however, a combination of simulated flow of Atlantic water into the Barents Sea and local primary production accounts for 70% of the variability with a 3-year lead. The associated regression predicts increased recruitment between 2007 and 2008 from about 450–700 million individuals with a standard error of nearly 150 million.  相似文献   

Temporal and spatial variability of phytoplankton and chlorophyll a: lessons from the south coast of Norway and the Skagerrak     

Dahl  Einar; Johannessen  Tore 《ICES Journal of Marine Science》1998,55(4):680-687

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Solution of great systems of normal equations     

Einar Andersen 《Journal of Geodesy》1950,24(1):19-29

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Temperature scenarios for Norway: from regional to local scale     

Torill Engen-Skaugen  Jan Erik Haugen  Ole Einar Tveito 《Climate Dynamics》2007,29(5):441-453

Scenarios with daily time resolution are frequently used in research on the impacts of climate change. These are traditionally developed by regional climate models (RCMs). The spatial resolution, however, is usually too coarse for local climate change analysis, especially in regions with complex topography, such as Norway. The RCM used, HIRHAM, is run with lateral boundary forcing provided from two global medium resolution models; the ECHAM4/OPYC3 from MPI and the HadAM3H from the Hadley centre. The first is run with IPCC SRES emission scenario B2, the latter is run with IPCC SRES emission scenarios A2 and B2. All three scenarios represent the future time period 2071–2100. Both models have a control run, representing the present climate (1961–1990). Daily temperature scenarios are interpolated from HIRHAM to Norwegian temperature stations. The at-site HIRHAM-temperatures, both for the control and scenario runs, are adjusted to be locally representative. Mean monthly values and standard deviations based on daily values of the adjusted HIRHAM-temperatures, as well as the cumulative distribution curve of daily seasonal temperatures, are conclusive with observations for the control period. Residual kriging are used on the adjusted daily HIRHAM-temperatures to obtain high spatial temperature scenarios. Mean seasonal temperature grids are obtained. By adjusting the control runs and scenarios and improving the spatial resolution of the scenarios, the absolute temperature values are representative at a local scale. The scenarios indicate larger warming in winter than in summer in the Scandinavian regions. A marked west–east and south–north gradient is projected for Norway, where the largest increase is in eastern and northern regions. The temperature of the coldest winter days is projected to increase more than the warmer temperatures.  相似文献   

New gas geothermometers for geothermal exploration—calibration and application     

Stefán Arnórsson  Einar Gunnlaugsson 《Geochimica et cosmochimica acta》1985,49(6):1307-1325

Calibration of five gas geothermometers is presented, three of which used CO₂, H₂S and H₂ concentrations in fumarole steam, respectively. The remaining two use $\text{CO}{}_2\text{H}{}_2$ and $\text{H}{}_2\text{S}\text{H}{}_2$ ratios. The calibration is based on the relation between gas content of drillhole discharges and measured aquifer temperatures. After establishing the gas content in the aquifer, gas concentrations were calculated in steam formed by adiabatic boiling of this water to atmospheric pressure to obtain the gas geothermometry functions. It is shown that the concentrations of CO₂, H₂S and H₂ in geothermal reservoir waters are fixed through equilibria with mineral buffers. At temperatures above 230°C epidote + prehnite + calcite + quartz are considered to buffer CO₂. Two buffers are involved for H₂S and H₂ and two functions are, therefore, presented for the geothermometers involving these gases. For waters containing less than about 500 ppm chloride and in the range 230–300°C pyrite + pyrrholite + epidote + prehnite seem to be involved, but pyrite + epidote + prehnite + magnetite or chlorite for waters above 300°C and waters in the range 230–300°C, if containing over about 500 ppm.The gas geothermometers are useful for predicting subsurface temperatures in high-temperature geothermal systems. They are applicable to systems in basaltic to acidic rocks and in sediments with similar composition, but should be used with reservation for systems located in rocks which differ much in composition from the basaltic to acidic ones. The geothermometry results may be used to obtain information on steam condensation in upflow zones, or phase separation at elevated pressures.Measured aquifer temperatures in drillholes and gas geothermometry temperatures, based on data from nearby fumaroles, compare well in the five fields in Iceland considered specifically for the present study as well as in several fields in other countries for which data were inspected. The results of the gas geothermometers also compare well with the results of solute geothermometers and mixing models in three undrilled Icelandic fields.  相似文献   

Estimation of geological dip and curvature from time‐migrated zero‐offset reflections in heterogeneous anisotropic media     

Martin Tygel  Bjørn Ursin  Einar Iversen  Maarten V. de Hoop 《Geophysical Prospecting》2012,60(2):201-216

Starting from a given time‐migrated zero‐offset data volume and time‐migration velocity, recent literature has shown that it is possible to simultaneously trace image rays in depth and reconstruct the depth‐velocity model along them. This, in turn, allows image‐ray migration, namely to map time‐migrated reflections into depth by tracing the image ray until half of the reflection time is consumed. As known since the 1980s, image‐ray migration can be made more complete if, besides reflection time, also estimates of its first and second derivatives with respect to the time‐migration datum coordinates are available. Such information provides, in addition to the location and dip of the reflectors in depth, also an estimation of their curvature. The expressions explicitly relate geological dip and curvature to first and second derivatives of reflection time with respect to time‐migration datum coordinates. Such quantitative relationships can provide useful constraints for improved construction of reflectors at depth in the presence of uncertainty. Furthermore, the results of image‐ray migration can be used to verify and improve time‐migration algorithms and can therefore be considered complementary to those of normal‐ray migration. So far, image‐ray migration algorithms have been restricted to layered models with isotropic smooth velocities within the layers. Using the methodology of surface‐to‐surface paraxial matrices, we obtain a natural extension to smooth or layered anisotropic media.  相似文献   

Estimation of geological dip and reflector curvature from zero-offset seismic reflections in heterogeneous anisotropic media     

Martin Tygel  Bj?rn Ursin  Einar Iversen  Maarten V. de Hoop 《Studia Geophysica et Geodaetica》2012,56(2):521-531

Depth conversion of selected seismic reflections is a valuable procedure to position key reflectors in depth in a process of constructing or refining a depth-velocity model. The most widespread example of such procedure is the so-called map migration, in which normal-incidence, zero-offset (stacked) seismic data are employed. Since the late seventies and early eighties, under the assumption of an isotropic velocity model, map migration algorithms have been devised to convert traveltime and its first and second derivatives into reflector position, dip and curvatures in depth. In this work we revisit map migration to improve the existing algorithms in the following accounts: (a) We allow for fully anisotropic media; (b) In contrast to simple planar measurement surface, arbitrary topography is allowed, thus enlarging the algorithms applicability and (c) Derivations and results are much simplified upon the use of the methodology of surface-to-surface paraxial matrices.  相似文献   

Ray tracing and inhomogeneous dynamic ray tracing for anisotropy specified in curvilinear coordinates     

Einar Iversen  Ivan P&#;en&#;ík 《Geophysical Journal International》2008,174(1):316-330

Ray tracing has recently been expressed for anisotropy specified in a local Cartesian coordinate system, which may vary continuously in a model specified by elastic parameters. It takes advantage of the fact that anisotropy is often of a simpler nature locally (and is thus specified by a smaller number of elastic parameters) and that the orientation of its symmetry elements may vary. Here we extend this approach by replacing the local Cartesian coordinate system with a curvilinear coordinate system of global extent and by applying the new approach to ray tracing and inhomogeneous dynamic ray tracing. The curvilinear coordinate system is orthogonal and is constructed so that the coordinate axes are consistent with the considered anisotropy of the medium. Our formulation allows for computation of ray attributes (e.g. ray velocity vector and paraxial ray attributes) in the curvilinear coordinate system, while rays are computed in global Cartesian coordinates. Compared to the classic formulation in terms of 21 elastic moduli in global Cartesian coordinates, the main advantages are improved efficiency, lower computer-memory requirements, and conservation of anisotropic symmetry throughout the model.  相似文献   

On the Nature of Prominence Absorption and Emission in Highly Ionized Iron and in Neutral Hydrogen     

Engvold  Oddbjørn  Jakobsson  Hans  Tandberg-Hanssen  Einar  Gurman  Joe B.  Moses  Daniel 《Solar physics》2001,202(2):293-308

We have studied the behavior of the emission in the highly ionized EUV lines Feix/x, 171 Å, Fexii, 195 Å, and Fexv, 284 Å observed in quiescent prominences. Kucera, Andretta, and Poland (1998) have explained the absorption of other highly ionized metallic EUV lines as due to absorption in the hydrogen continuum. However, since the authors noticed deviations from the expected ³ dependence of the absorption strengths, we have explored the possibility that emission in EUV iron lines can influence the observations. We propose the existence of a hot, i.e., million-degree plasma component of the prominence–corona transition region (PCTR), where the EUV iron lines originate. We find that (i) neither of the two scenarios alone reproduces observations; (ii) both emission and absorption increase prior to eruption; (iii) the measurements of Kucera, Andretta, and Poland's 14 May event are strongly affected by hot PCTR emission.  相似文献