Modeling of ocean wave propagation across the crevasse-ridden ice shelf: focus on the comparison of two models

<p>The propagation of high-frequency elastic-flexural waves through an ice shelf was modeled by a full 3-D elastic models. These models based on the momentum equations that were written as the differential equations (model#1) and as the integro-differential equations (model#2). The integro-differential form implies the vertical integration of the momentum equations from the ice surface to the current coordinate z like, for instance, in the Blatter-Pattyn ice flow model. The sea water flow under the ice shelf is described by the wave equation. The numerical solutions were obtained by a finite-difference method. Numerical experiments were undertaken for a crevasse-ridden ice shelf with different spatial periodicities of the crevasses. In this research the modeled positions of the band gaps in the dispersion spectra dependently on the spatial periodicities of the crevasses is investigated from the point of view of agreement of these positions with the Bragg’s law. The investigation of the dispersion spectra shows that different models reveal different sensitivities of the dispersion spectra (in relation to the appearance of the band gaps in the spectra) dependently on the spatial periodicity of the crevasses and on the crevasses depth.</p>

Late Paleozoic oroclinal bending, arc amalgamation, and large-scale transcurrent tectonics in the western Central Asian Orogenic Belt: termination of accretionary orogenesis and initiation of aridification in Central Asia?

<p>The western Central Asian Orogenic Belt (CAOB) underwent the prolonged accretion from Neoproterozoic to latest Paleozoic, and evolved into an intracontinental orogenic environment in the Mesozoic to Cenozoic, which was accompanied by significant changes of climatic environments. To constrain earlier accretion mechanisms and processes of the CAOB is fundamentally important given its control on the orogenic architecture and paleogeography, which inevitably affects the subsequent intracontinental orogeny. Here, I focus on the late Paleozoic tectonic reconstruction of the western CAOB with an aim to understand the role of oroclinal bending, arc amalgamation, and large-scale transcurrent tectonics in shaping the orogenic architecture of the western CAOB. My results show that the development of the U-shaped Kazakhstan Orocline in the western CAOB may have been controlled by the along-strike variation of the trench retreat, which was accompanied by the consumption of the Junggar Ocean in the core area of the orocline. The subsequent amalgamation of multiple arcs in the western CAOB may further amplify the oroclinal structure, and I emphasize that the orogen-parallel extension plays a significant role in arc amalgamation of the western CAOB. In the Permian, the large scale of strike-slip faults characterized the western CAOB with sinistral shearing in the north (Chinese Altai) and dextral kinematics in the south (Tianshan), which together indicates the eastward migration of orogenic materials (current coordinate). Following the termination of accretionary orogeny, the western CAOB was in an intracontinental environment with relatively arid climate in the early to middle Triassic as indicated by the widespread occurrence of red beds, which may mark the initiation of aridification in Central Asia.</p><p>Acknowledgements: this study was financially supported by the Hong Kong Research Grant Council (HKU17302317), the international partnership program of the Chinese Academy of Sciences (132744KYSB20200001), the National Key Research and Development Program of China (2017YFC0601205), the National Natural Science Foundation of China (41872222) and a project from Guangdong Province (2019QN01H101).</p>

Digital processing of old topographical maps for the reference base for quantitative and qualitative studies of landscape changes

<p><strong>Abstract.</strong> The undertaken issue was the digital processing of cartographic material such as Prussian old topographical maps from the beginning and the end of the XIX century. These maps play a crucial role in studies of the development of the landscape in the past. Quantitative and qualitative changes in geographical space could be analyzed after the transformation of historical material according to the present day coordinate system.</p><p>The main source of data were two types of Prussian topographical maps &amp;ndash; Urmesstischblätter which represents topographical features from the 1820s and Messtischblätter which depicts the landscape from the 1880s and were based on more precise measurements. These two maps were drawn in the 1&amp;thinsp;:&amp;thinsp;25&amp;thinsp;000 scale and because of that they are very useful in comparative analysis. Regions presented on them are the Upper Silesia Industrial District and the Ruhr Area.</p><p>The main aim of this research was to design and develop a reference basis for further quantitative and qualitative studies of landscape changes in two mentioned regions. The research included a set of methods such as georeferencing old maps based on the current coordinate system, vectorization of the selected geographical features, unification of symbolization, and proofreading of prepared reference maps.</p><p>The processing of old cartographic maps was divided into stages which helped to achieve the main goals of the research and gave the results which were reference maps with uniformed style in one coordinate system. These reference maps have also become the basis for the creation of bargraphs of land usage, which are used to describe changes in selected elements of the landscape in individual time periods from 1830.</p>