Material Circulation through Time: Chemical Differentiation Within the Mantle and Secular Variation of Temperature and Composition of the Mantle

Author(s):  
Tsuyoshi Komiya
1998 ◽  
Vol 37 (6-7) ◽  
pp. 241-248 ◽  
Author(s):  
A. Netzband ◽  
H. Christiansen ◽  
B. Maaß ◽  
G. Werner

Besides the beneficial use of dredged material, sustainable relocation, which means keeping the sediments in the natural aquatic material circulation, is one goal for handling dredged material in the port of Hamburg. Decreasing contamination the River Elbe and new dredged material guidelines provide a basis for this. With comprehensive investigations, near- and far-field transport and the effects of relocation regarding the water quality and the benthic community were determined thus deveoloping conditions for future operating strategies.


2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Sabrina Sanchez ◽  
Johannes Wicht ◽  
Julien Bärenzung

Abstract The IGRF offers an important incentive for testing algorithms predicting the Earth’s magnetic field changes, known as secular variation (SV), in a 5-year range. Here, we present a SV candidate model for the 13th IGRF that stems from a sequential ensemble data assimilation approach (EnKF). The ensemble consists of a number of parallel-running 3D-dynamo simulations. The assimilated data are geomagnetic field snapshots covering the years 1840 to 2000 from the COV-OBS.x1 model and for 2001 to 2020 from the Kalmag model. A spectral covariance localization method, considering the couplings between spherical harmonics of the same equatorial symmetry and same azimuthal wave number, allows decreasing the ensemble size to about a 100 while maintaining the stability of the assimilation. The quality of 5-year predictions is tested for the past two decades. These tests show that the assimilation scheme is able to reconstruct the overall SV evolution. They also suggest that a better 5-year forecast is obtained keeping the SV constant compared to the dynamically evolving SV. However, the quality of the dynamical forecast steadily improves over the full assimilation window (180 years). We therefore propose the instantaneous SV estimate for 2020 from our assimilation as a candidate model for the IGRF-13. The ensemble approach provides uncertainty estimates, which closely match the residual differences with respect to the IGRF-13. Longer term predictions for the evolution of the main magnetic field features over a 50-year range are also presented. We observe the further decrease of the axial dipole at a mean rate of 8 nT/year as well as a deepening and broadening of the South Atlantic Anomaly. The magnetic dip poles are seen to approach an eccentric dipole configuration.


2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Magnus D. Hammer ◽  
Grace A. Cox ◽  
William J. Brown ◽  
Ciarán D. Beggan ◽  
Christopher C. Finlay

AbstractWe present geomagnetic main field and secular variation time series, at 300 equal-area distributed locations and at 490 km altitude, derived from magnetic field measurements collected by the three Swarm satellites. These Geomagnetic Virtual Observatory (GVO) series provide a convenient means to globally monitor and analyze long-term variations of the geomagnetic field from low-Earth orbit. The series are obtained by robust fits of local Cartesian potential field models to along-track and East–West sums and differences of Swarm satellite data collected within a radius of 700 km of the GVO locations during either 1-monthly or 4-monthly time windows. We describe two GVO data products: (1) ‘Observed Field’ GVO time series, where all observed sources contribute to the estimated values, without any data selection or correction, and (2) ‘Core Field’ GVO time series, where additional data selection is carried out, then de-noising schemes and epoch-by-epoch spherical harmonic analysis are applied to reduce contamination by magnetospheric and ionospheric signals. Secular variation series are provided as annual differences of the Core Field GVOs. We present examples of the resulting Swarm GVO series, assessing their quality through comparisons with ground observatories and geomagnetic field models. In benchmark comparisons with six high-quality mid-to-low latitude ground observatories we find the secular variation of the Core Field GVO field intensities, calculated using annual differences, agrees to an rms of 1.8 nT/yr and 1.2 nT/yr for the 1-monthly and 4-monthly versions, respectively. Regular sampling in space and time, and the availability of data error estimates, makes the GVO series well suited for users wishing to perform data assimilation studies of core dynamics, or to study long-period magnetospheric and ionospheric signals and their induced counterparts. The Swarm GVO time series will be regularly updated, approximately every four months, allowing ready access to the latest secular variation data from the Swarm satellites.


2021 ◽  
pp. 088832542095081
Author(s):  
Virág Molnár

This article belongs to the special cluster, “National, European, Transnational: Far-right activism in the 20th and 21st centuries”, guest edited by Agnieszka Pasieka. Research on populism attributes great significance to mapping the distinctive discursive logic of populist reasoning (e.g., the trope of pitting corrupt elites against the people). This article aims to move beyond the primary focus on discursive structures to stress the role of symbols, objects, and different modalities of circulation in the political communication of populist ideas, using the case of Hungary. By tracing the history of one of the key symbols of nationalist populism—the image of “Greater Hungary”—from its emergence in the interwar period to its present-day use, the article shows how the meanings and material forms this symbol assumed in political communication that evolved under different political regimes. The analysis builds on extensive archival, ethnographic, and online data to highlight how the diversity of material forms and the conduits through which this image circulated have contributed to its endurance as a key political symbol. Symbols, like the Greater Hungary image, condense complex historical narratives into a powerful sign that can be easily objectified, reproduced, and diffused. Today’s differentiated consumer markets provide convenient conduits for this kind of material circulation. These symbols carry meaning in and of themselves as signs, and once they are turned into everyday objects, they facilitate the normalization of radical politics by increasing their salience and broad visibility.


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