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Geoscience Frontiers 2015年第1期6卷 61-78页

作者： Yingfeng Ji Shoichi Yoshioka Research Center for Urban Safety and Security Kobe University Department of Earth and Planetary Science Graduate School of ScienceKobe University

We investigated the relationships among slab geometry, obliquity, and the thermal regime associated with the subduction of oceanic plates using a three-dimensional （3D） parallelepiped thermal convection model. Various models with convex and concave slab shapes were constructed in the numerical simu- lation, and the temperature and mantle flow distributions were calculated. The results revealed that when the slab dip angle increases, or the obliquity of subduction becomes steeper, the interplate tem- perature decreases remarkably. Cooler （warmer） zones on the plate interface were identified from the modeling where there was a larger （smaller） subduction angle. Consequently, the interplate temperature distribution is partly controlled by the true subduction angle （TSA）, which is a function of the slab dip angle and the obliquity of subduction. The rate of change of the interface temperature for the TSA was 10-50 ℃ （10°〈 TSA 〈 20°） at depths ranging from （TSA 10） × 5 km to 60 ＋（TSA 10） × 5 km for a fiat slab after a subduction history of 7 Myrs. The along-arc slab curvature affects the variation in TSA. The slab radius also appeared to influence the radius of induced mantle flow.

关键词： Temperature Mantle flow Heat flow Numerical simulation Slab geometry obliquity

River bank protection from ship-induced waves and river flow

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Water Science and Engineering 2019年第2期12卷 129-135页

作者： Sahameddin Mahmoudi Kurdistani Giuseppe R. Tomasicchin Felice D’Alessandro Leila Hassanabadi Department of Engineering for Innovation University of Salento

A new equation is proposed for the design of armor units on protected river banks under the combined action of ship-induced waves and river flow.Existing observed field and experimental data in the literature have been examined and a valuable database has been developed.Different conditions,including the river water depth,flow velocity,river bank slope,Froude number,wave height,wave period,and wave obliquity have been considered.Results from an empirical equation (Bhowmik,1978) that only considers the maximum wave height and river bank slope have been compared with the results calculated by the newly developed equation.Calculated results have also been verified against field data.Results show that not only the maximum wave height and river bank slope but also the water depth,flow velocity,wave length,wave obliquity,and wave period are important parameters for predicting the mean diameter of the armor units,highlighting the multivariate behavior of protecting the river bank in the presence of ship-induced waves and river flow velocity.

关键词： River bank protection Hydraulics Ship-induced waves River flow velocity Wave period Wave obliquity Multivariate phenomenon

Shuram-Wonoka carbon isotope excursion:Ediacaran revolution in the world ocean's meridional overturning circulation

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Geoscience Frontiers 2018年第2期9卷 391-402页

作者： George E.Williams Phillip W.Schmidt Department of Earth Sciences University of Adelaide MagneticEarth

The late Ediacaran Shuram-Wonoka excursion, with δ^(13)C_(carb) values as low as-12‰(PDB) in marineshelf deposits and spanning up to 10 Myr, is the deepest and most protracted δ^(13)C_(carb) negative anomaly recognised in Earth history. The excursion formed on at least four continents in low(≤32°) palaeolatitudes, and in China is associated with a major phosphogenic event. Global and intrabasinal correlation, magnetostratigraphy, isotope conglomerate tests and further geochemical data are consistent with a primary or syn-depositional origin for the excursion. Continental-margin phosphorites are generated by oceanic upwelling driven by surface winds, and δ^(13)C_(carb) negative anomalies are explicable by oceanic upwelling of 13 C-depleted deep oceanic waters, arguing that a feature common to these exceptional Ediacaran events was unprecedented perturbation of the world ocean. These events occurred during the transition from an alien Proterozoic world marked by low-palaeolatitude glaciation near sea level and strong seasonality to the familiar Phanerozoic Earth with circum-polar glaciation and temperate climate, suggesting that the Shuram-Wonoka excursion is related to this profound change in Earth's climate system. Of various hypotheses for Proterozoic low-palaeolatitude glaciation, only the high obliquity(>54°) hypothesis, which posits secular decrease in obliquity to near the present-day value(23.5°) during the Ediacaran, predicts an unparalleled revolution in the Ediacaran world ocean. The obliquity controls the sense of the world ocean's meridional overturning circulation, which today is driven by the sinking of cold, dense water at the poles and upwelling driven by zonal surface winds.When the decreasing obliquity passed the critical value of 54° during the Ediacaran the meridional temperature gradient reversed, with the equator becoming warmer than the poles and Hadley lowlatitude(<30°-35°) atmospheric zonal circulation reversing. This reversal of the temperature gradient is unique to the Ediacaran Period a

关键词： Ediacaran ShurameWonoka carbon isotope excursion Oceanic meridional circulation Atmospheric circulation Proterozoic paleoclimate obliquity of the ecliptic

The Effect of Tide on the Global Climate Change

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Global Geology 2002年第1期7卷 23-30页

作者： YANG Xuexiang, CHEN Zhen and CHEN Dianyou( College of Ceo - exploration Science and Technology, Jilin University, Changchun 130026, P. R. China)Qiao Qiyuan(National Astronomical Observatory, Chinese Academy of Science, Beijing 100012, P. R. China) College of Geo - exploration Science and Technology Jilin University Changchun130026 P.R. China National Astronomical Observatory Chinese Academy of Science Beijing100012 P.R. China

The differential rotation between the solid and fluid spheres caused by tidal force could explain the 1500 to 1800-year cycle of the world's temperature. Strong tide increases the vertical and horizontal mixing of water in the oceans, drawing the cold Pacific water from the depths to the surface and the warm water from the west to the east, where it cools or warms the atmosphere above, absorbs or releases CO2 to decrease or increase greenhouse effect and to make La Nina or El Nino occur in the global. The moon's declination and obliquity of the ecliptic affect the tidal intensity. The exchange of tidal energy and tide-generating force caused by the sun, moon and major planets makes the earth's layers rotate in different speeds. The differenti-al rotation between solid and fluid of the earth is the basic reason for El Nino and global climate change.

关键词： Tide-generating force, Differential rotation, El Nino, Moon's declination, obliquity of the ecliptic

Late Neogene evolution of the East Asian monsoon revealed by terrestrial mollusk record in Western Chinese Loess Plateau:From winter to summer dominated sub-regime

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Late Neogene evolution of the East Asian monsoon revealed by...