Seasonal variability of the carbon export in the central South China Sea

Ocean Dynamics - The South China Sea (SCS) is strongly influenced by the East Asian monsoon system with seasonal reversal. Measurements from a 7-year continuous sediment trap located in the central...     

乌加河地震台地电阻率干扰形态识别

选取乌加河地震台2015-2018年地电阻率观测资料,分析数据异常变化,结合观测环境及实地调查,发现存在降雨、雷电、金属管线、农田灌溉、设备漏电等影响因素,对比分析并总结各类干扰曲线形态、变化幅度、影响时间、干扰频次等特征,以便正确认识并排除地电阻率干扰,为地震异常信息识别提供帮助。     

Remote sensing linear trends of the Gulf Stream from 1993 to 2016

Ocean Dynamics - The Gulf Stream (GS) transports a massive amount of heat northward to high latitudes and releases sensible and latent heat to the atmosphere, playing an important role in the North...     

Geochemistry,Zircon U–Pb Analysis,and Biotite 40Ar/39Ar Geochronology of the Maoling Gold Deposit,Liaodong Rift,NE China

The Maoling gold deposit is located in the southwestern part of the Liaodong rift, NE China, and has estimated reserves of 25 t. In this paper we present the results of an investigation into the geochronology and geodynamic mechanisms of igneous activity and metallogenesis within the Maoling gold deposit. New zircon U–Pb age data, biotite ⁴⁰Ar/³⁹Ar age data, whole‐rock geochemistry, and Hf isotopic analyses are presented in order to constrain the petrogenesis and mineralization of the deposit. Zircon U–Pb dating of the Wolongquan biotite monzogranite and Maoling biotite granite yielded mean ages of 194.0 ± 1.1 Ma and 196.1 ± 1.1 Ma, respectively. All the granites are characteristically high‐K calc‐alkaline, enriched in light rare earth elements and large ion lithophile elements, and depleted in high field strength elements, which is consistent with the geochemical characteristics of arc‐type magmas. The Hf isotope characteristics indicate that the granites formed by partial melting of early Paleoproterozoic crustal material. In addition, biotite ⁴⁰Ar/³⁹Ar dating indicates that the Maoling gold deposit formed at 188.9 ± 1.2 Ma, implying that the mineralization was related to both the granite intrusions. Taking into account previous data on S–Pb–O–H isotopes and our new age data, the Maoling deposit can be classified as an intrusion‐related gold deposit. Taking into account the geology of the study area and adjacent regions, we propose that the Maoling gold deposit and its associated granitic intrusions formed in a geodynamic setting that was dominated by subduction of the Paleo‐Pacific Plate beneath the Eurasian continent.     

民勤荒漠绿洲过渡带灌丛沙堆形态特征及分布格局

以民勤荒漠绿洲过渡带为研究区,通过样方调查,研究了荒漠区、荒漠绿洲过渡区到绿洲内不同梯度生境中灌丛沙堆的形态特征及分布格局。结果表明:(1)3种生境中灌丛沙堆的形态呈极显著性差异(p<0.01);绿洲区灌丛沙堆的平均高度、底面积、纵横断面积和体积均最大,其次为荒漠区,过渡区最小。(2)过渡带3种生境灌丛沙堆的长、短轴之间均呈二次函数关系,但相关程度不同,过渡区相关性最高,相关系数达0.78;绿洲区相关性最低,相关系数为0.57;高度与底面积、体积与高度间均呈幂函数关系,相关系数均在0.59以上;(3)过渡区灌丛沙堆分布密度较大,呈聚集分布,而荒漠区及绿洲区沙堆分布密度较小,均呈随机分布。     

A model study of the Copper River plume and its effects on the northern Gulf of Alaska

A three-level nested Regional Ocean Modeling System was used to examine the seasonal evolution of the Copper River (CR) plume and how it influences the along- and across-shore transport in the northern Gulf of Alaska (NGoA). A passive tracer was introduced in the model to delineate the growth and decay of the plume and to diagnose the spread of the CR discharge in the shelf, into Prince William Sound (PWS) and offshore. Furthermore, a model experiment with doubled discharge was conducted to investigate potential impacts of accelerated glacier melt in future climate scenarios. The 2010 and 2011 simulation revealed that the upstream (eastward) transport in the NGoA is negligible. About 60 % of the passive tracer released in the CR discharge is transported southwestward on the shelf, while another one third goes into PWS with close to 60 % of which exiting PWS to the shelf from Montague Strait. The rest few percent is transported across the shelf break and exported to the GoA basin. The downstream transport and the transport into PWS are strongly regulated by the downwelling-favorable wind, while the offshore transport is related to the accumulation of plume water in the shelf, frontal instability, and the Alaskan Stream. It takes weeks in spring for the buoyancy to accumulate so that a bulge forms outside of the CR estuary. The absence of strong storms as in the summer of 2010 allows the bulge continue growing to trigger frontal instability. These frontal features can interact with the Alaskan Stream to induce transport pulses across the shelf break. Alternatively as in 2011, a downwelling-favorable wind event in early August (near the peak discharge) accelerates the southwestward coastal current and produces an intense downstream transport event. Both processes result in fast drains of the buoyancy and the plume content, thereby rapid disintegration of the plume in the shelf. The plume in the doubled discharge case can be two to three times in size, which affects not only the magnitude but also the timing of certain transport events. In particular, the offshore transport increases by several folds because the plume appears to be more easily entrained by the seaward flow along the side of Hinchinbrook Canyon.     

Study on Three-dimensional Visualization for Rock Structure

The visualization of rock structure is a very useful and important technique in many aspects in geological and geotechnical engineering such as investigating and evaluating the stability of a high rock slope. The conventional method used to visualize rock structure is limited to plotting the orientation of individual discontinuities by using the Schmidt stereographic net. The present paper shows a new technique to visualize the three-dimensional structure of rock masses. The fitting function for three-dimensional rock structure was established based on data gathered from field survey. Two fitting methods by which the discontinuous points gathered from a plane and discrete points from field survey were fitted respectively are suggested. The technique to visualize the three-dimensional structure of rock masses includes many aspects such as projection transformation, blanking and mutual cutting, are investigated. Based on the visualizing technique, the rock structure at the site of Xilupdu dam which is being built in Southwest of China was investigated.     

Modeling the long-term variability of phytoplankton functional groups and primary productivity in the South China Sea

Primary productivity (PP) and phytoplankton structure play an important role in regulating oceanic carbon cycle. The unique seasonal circulation and upwelling pattern of the South China Sea (SCS) provide an ideal natural laboratory to study the response of nutrients and phytoplankton dynamics to climate variation. In this study, we used a three-dimensional (3D) physical–biogeochemical coupled model to simulate nutrients, phytoplankton biomass, PP, and functional groups in the SCS from 1958 to 2009. The modeled results showed that the annual mean carbon composition of small phytoplankton, diatoms, and coccolithophores was 33.7, 52.7, and 13.6 %, respectively. Diatoms showed a higher seasonal variability than small phytoplankton and coccolithophores. Diatoms were abundant during winter in most areas of the SCS except for the offshore of southeastern Vietnam, where diatom blooms occurred in both summer and winter. Higher values of small phytoplankton and coccolithophores occurred mostly in summer. Our modeled results indicated that the seasonal variability of PP was driven by the East Asian Monsoon. The northeast winter monsoon results in more nutrients in the offshore area of the northwestern Luzon Island and the Sunda Shelf, while the southwest summer monsoon drives coastal upwelling to bring sufficient nutrients to the offshore area of southeastern Vietnam. The modeled PP was correlated with El Niño/Southern Oscillation (ENSO) at the interannual scale. The positive phase of ENSO (El Niño conditions) corresponded to lower PP and the negative phase of ENSO (La Niña conditions) corresponded to higher PP.     

Residents′Activity-travel Behavior Variation by Communities in Beijing,China

China’s transition from a planned economy to a market economy has resulted in many changes in its urban structure and society and provided an opportunity for a quasi-longitudinal case study on the relationship between the built environment and activity-travel behavior.This paper draws upon data from an activity diary survey conducted in Beijing in 2007.The survey sample comprised 652 residents living in Danwei(work unit),commodity housing,and affordable housing neighborhoods.On the basis of the three-dimensional geo-visualization analysis of the space-time path and statistical multivariate regression models of daily travel and leisure time,it was found that both residential spatial factors and socio-demographics influence residents’ daily behaviors.The findings show that Danwei residents have less daily travel time than those who live in commodity housing,but people living in affordable housing endure the longest travel time.Daily leisure time is associated more with individual attributes.We argue that although China’s transition is currently gradual,the Danwei system may continue to play significant roles in daily life,and it might provide a valuable model for neighborhood spatial planning.     

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