Ra in the Japan Sea and the residence time of the Japan Sea water     

Koh Harada  Shizuo Tsunogai 《Earth and Planetary Science Letters》1986,77(2)

The surface water of the Japan Sea contained²²⁶Ra of70 ± 4dpm m⁻³ which was nearly equal to that of the surface water in the North Pacific. The concentration of²²⁶Ra in the Japan Sea deep water below 500 m was151 ± 8dpm m⁻³, showing a vertically and regionally small variation. This concentration of²²⁶Ra in the deep water is unexpectedly high, because the Japan Sea deep water has a higher Δ¹⁴ C value by about 50‰ than the Atlantic deep water containing the same²²⁶Ra. One of the causes to be considered is larger contribution of²²⁶Ra from biogenic particles dissolving in the Japan Sea deep water, but the Japan Sea is not so fertile in comparison to the Bering Sea. The other more plausible cause is the internal ventilation of the Japan Sea water, which means that the residence time of the Japan Sea Proper water is considerably long although the water is vertically mixed fairly well especially in winter. The ventilation may supply some amounts of radiocarbon and oxygen but does not change the inventory of²²⁶Ra. The residence times of the Japan Sea deep water and of water within the Japan Sea are calculated by solving simultaneous equations for²²⁶Ra and¹⁴C with a three-box model to be 300–400 years and 700–1000 years, respectively.  相似文献   

Topographical effects on the distributions of rainfall and 18O distributions: a case in Miyake Island,Japan     

Changyuan Tang  Shizuo Shindo  Isao Machida 《水文研究》1998,12(4):673-682

In this paper, we try to calculate precipitation in Miyake Island, Japan. In order to know the temporal and spatial variations of precipitation, we have set 15 rain gauges randomly in the island to collect the monthly precipitation data since June 1994. It is found that the precipitation is very different from point to point. First, we used statistical methods to get the correlations between the monthly precipitation at our survey points and that at the weather station. Next, regression analyses were used to establish formulae to calculate precipitation as a function of altitude, aspect of the geomorphological surface and wind direction. Based on these results, distributions of monthly and yearly precipitation and δ¹⁸O over the island were assessed. The results show that landscape patterns strongly influence precipitation distribution over the island, with the highest precipitation being found on the windward side, about 400–600 m above sea level. Even at places at the same altitude, the precipitation was different because of the aspect of the landscape. At the same time, altitude effects for δ¹⁸O on both the windward and leeward sides were −0·10‰/100 m and −0·15‰/100 m, respectively. Comparing with the distribution of precipitation distribution, it was also found that δ¹⁸O for the windward and leeward sides was different from that for precipitation, which means that both topographical effects must be considered separately. © 1998 John Wiley & Sons, Ltd.  相似文献   

Arsenic species and their accumulation features in green turtles (Chelonia mydas)     

Agusa T  Takagi K  Iwata H  Tanabe S 《Marine pollution bulletin》2008,57(6-12):782-789

Total arsenic (As) and its compounds were determined in liver, kidney, muscle, and stomach contents of green turtles (Chelonia mydas). Total As concentrations in the muscle were higher than those in the kidney and liver. Arsenobetaine (AB) was the predominant compound in all the three tissues and its levels were positively correlated with total As concentrations. This indicates that AB greatly contributes to As accumulation in green turtles. Higher concentrations of remaining As in the sample after extraction were detected in the liver, implying that lipid-soluble or protein bound As compounds accumulate in the liver of green turtles. Total As levels in tissues showed significant negative correlations with standard carapace length. The size-dependence of As accumulation in green turtles may be related to their feeding habit, shifting from carnivore to herbivore at different growth stages. Concentrations of AB and dimethylarsinic acid (DMA) were low in the stomach contents but high in the tissues, implying bioaccumulation of these arsenicals in green turtles.  相似文献   

3D Modal Solution for Tidally Induced Lagrangian Residual Velocity with Variations in Eddy Viscosity and Bathymetry in a Narrow Model Bay     

DENG Fangjing  JIANG Wensheng  VALLE-LEVINSON Arnoldo  FENG Shizuo 《中国海洋大学学报(英文版)》2019,(1):69-79

In this study, we examine the results obtained by the Finite-volume Coastal Ocean Circulation Model(FVCOM) regarding the effects of eddy viscosity and bathymetry on the three-dimensional(3 D) Lagrangian residual velocity(LRV) in a narrow bay. The results are cast in terms of two nondimensional numbers: the ratio of friction to local acceleration(δ) and the ratio of the minimum depth over shoals to the maximum depth in the channel(ε). The ratio δ depends on the eddy viscosity and mean depth. For a given eddy viscosity, when ε > 0.5, the along-estuary LRV tends to be vertically sheared and when ε < 0.5, the exchange is laterally sheared. When ε << 1, the structure of the 3 D, depth-integrated, and breadth-averaged LRV changes only slightly as δ increases. For ε values between 0.33 and 0.5, the structure of the 3 D LRV is mainly laterally sheared. In the same ε range, the 3 D and depth-integrated LRV exhibit reversed structures from high to low δ values. In addition, the breadth-averaged LRV weakens the typical twolayered circulation when δ decreases. When ε is 1, the two-layered vertical structure reverses direction, and a three-layered vertical structure develops in the outer bay as δ decreases.  相似文献   

3.2 ka BP以来念青唐古拉山东部则普冰川波动与环境变化   总被引：4，自引：1，他引：3  

焦克勤  Shuji Iwata  姚檀栋  井哲帆  李忠勤 《冰川冻土》2005,27(1):74-79

基于野外考察和 14C 年代测定, 确定了3.2 ka BP以来念青唐古拉山东部则普冰川的冰进序列.新冰期冰进可明显分为3次: 即大拿[ 14C ( 3 242 ±101)a BP]、大拿顶[ 14C ( 1 920 ±110)～ (1 540 ±85)a BP]和白同[ 14C ( 1 056 ±115)a BP]冰进.新冰期盛时, 则普冰川比现代长6.9 km, 面积大17.10 km2, 雪线降低约157 m, 温度降低1.0～1.9 ℃. 小冰期可分出2次: 即15世纪或16世纪[ 14C (580±130)a BP]和19世纪[ 14C (197±80)a BP, (190±80)a BP]冰进. 小冰期盛时, 则普冰川比现代长2.0 km, 面积大11.16 km2, 雪线降低约100 m, 温度降低0.65～1.23 ℃. 现代则普冰川, 冰面表碛特别发育, 其厚度亦很大, 冰舌末端退缩难以辨认. 但冰川减薄很强烈, 边缘两侧形成2～3道现代侧碛, 并高出现代冰面20～30 m. 对埋藏腐殖质土壤层和木炭碎屑经 14C 年代测定, 结果表明在(720±210)～( 2 010 ±120)a BP间, 波堆藏布流域存在砍伐森林、开垦田地和放牧的人类活动.  相似文献   

亚洲沙尘的远距离输送及对海洋生态系统的影响   总被引：6，自引：0，他引：6  

高会旺  祁建华  石金辉  石广玉  冯士筰 《地球科学进展》2009,24(1):1-10

亚洲沙尘是全球沙尘的重要组成部分,其环境效应已得到广泛关注,但至今对亚洲沙尘输送/沉降—海洋生态系统响应—辐射活性气体海气交换—间接气候效应这一过程的认识却是非常初步的。亚洲沙尘存在3个主要源区,对其排放强度的认识仍存在较大的不确定性。亚洲沙尘可以通过长距离输送而影响到广大的北太平洋,其传输路径和影响范围决定于沙尘的来源、粒子谱分布与大气环流特征等因素。沙尘沉降是海洋营养物质和污染物质的来源之一,但沉降通量的估算结果仍有待进一步验证,而对海洋生态系统的作用机制及其反馈还缺乏足够的了解。论文在综述国内外相关研究的基础上,提出了“亚洲沙尘与海洋生态系统”（Asian Dust and Ocean EcoSystem,ADOES）研究计划的科学目标和主要研究内容。  相似文献   

Aturoidea (Nautilida) from the Upper Cretaceous Sada limestone in Shimanto City, Kochi Prefecture, Japan     

Yasuyuki Tsujino  Hirohide Iwata 《Cretaceous Research》2009,30(4):911-916

The first specimen of Aturoidea to be recorded in East Asia has been found in the Upper Cretaceous Sada limestone in Shimanto City, Kochi Prefecture, Japan. The specimen is one of the few representatives from the Upper Cretaceous, along with species known from Libya, Angola, and India. The specimen is very similar to A. mathewsonni from the Paleocene deposits in California. However, we describe the specimen as A. cf. mathewsonni, as it slightly differs from A. mathewsonni in the shape of the lateral lobe of the suture. The finding reveals that Aturoidea had already lived in waters around East Asia in the Late Cretaceous.  相似文献   

Accumulation of trace elements in harp seals (Phoca groenlandica) from Pangnirtung in the Baffin Island, Canada     

Agusa T  Nomura K  Kunito T  Anan Y  Iwata H  Tanabe S 《Marine pollution bulletin》2011,63(5-12):489-499

Nineteen trace elements were determined in liver, muscle, kidney, gonads, and hair of 18 harp seals (Phoca groenlandica) from Pangnirtung in the Baffin Island, Canada. Concentrations of V, Mn, Fe, Cu, Mo, Ag, and Hg in the liver, Co, Cd, and Tl in the kidney, and Ba and Pb in the hair were significantly higher than those in other tissues. Significant positive correlations between Hg concentrations in the hair, and liver, kidney and testis imply usefulness of the hair sample for non-destructive monitoring of Hg in the harp seals. It is suggested that whereas Hg preferentially accumulates in the liver, the accumulation in other tissues is induced at higher hepatic Hg levels. In contrast, Se may not be accumulated in other tissues compared with the liver even at higher hepatic Hg levels because of the presence of excess Se for Hg detoxification in other tissues.  相似文献   

Pelagic Nitrogen Cycling in Jiaozhou Bay, a Model Study I： the Conceptual Model   总被引：2，自引：0，他引：2  

任玲  张曼平  Brockmann Uwe H  冯士笮 《中国海洋湖沼学报》2003,21(4):358-367

A zero-dimensional box model (PNCMjzb) with six state variables (ammonium, nitrate, dissolved organic nitrogen, phytoplankton, zooplankton and detritus) was developed to study nitrogen cycling in the Jiaozhou Bay pelagic ecosystem. The dominant processes within these compartments are considered with nitrogen as flow currency. Phytoplankton and zooplankton are treated as separate state variables, assuming that the species composition was dominated by two or three species the dynamic constants of which are similar and that they represent the entire plankton community. The microbial loop has not been integrated explicitly in the model. The turnover of bacteria is included implicitly in processes such as detritus decomposition, DON remineralization, pelagic nitrification and denitrification. The model is driven by two forcing variables, viz. water temperature and light intensity. Historical data from the1980s and 1990s were compiled and used for model calibration. In this paper (part Ⅰ), the consideration of every main compartment in the model is interpreted in detail. And the applied equations and parameters are presented. The main results from the simulations together with discussion about phytoplankton dynamics and primary production in Jiaozhou Bay are presented in the next paper (part Ⅱ).  相似文献   

Acquisition of the tide-induced Lagrangian residual current field by the PIV technique in the laboratory     

Tao Wang  Wensheng Jiang  Xu Chen  Shizuo Feng 《Ocean Dynamics》2013,63(11-12):1181-1188

In this paper, a new particle image velocimetry (PIV)-based measurement method is proposed to obtain the high-resolution tide-induced Lagrangian residual current field in the laboratory. A long gravity wave was generated to simulate the tide in a narrow tank full of water laden with PIV particles. Consecutive charge-coupled device (CCD) images were recorded with the studied layer illuminated with a laser beam. Two images separated by one tidal period were processed by applying the pattern-matching algorithm to get the horizontal tide-induced Lagrangian residual current field. The results coincide with sporadic results from the traditional surface-float tracing method, but with much higher spatial resolution and accuracy. Furthermore, it is found that the direct acquisition of the Lagrangian residual current may reduce the error at least by one order compared with those acquisition methods that require the detailed information of the tidal cycle.  相似文献