Relationship between Cd and PO4 in the Subtropical Sea near the Ryukyu Islands

The relationship between dissolved cadmium (Cd) and phosphate (PO₄) was examined at three stations in the subtropical area near the Ryukyu Islands in May 1999. Preformed PO₄ was obtained using the Redfield ratio in order to separate the surface water and the other layers in this study area. Almost 0 μM (−0.043 μM to 0.094 μM) was estimated in the layers above 300 m and 250 m at Sts. 1 and 3 and at St. 2, respectively. Up to these depths, water was considered to be uniform, and these layers were defined as the surface water in this study area. In the surface water, the slopes of the regression lines of the Cd-PO₄ plot were 0.162, 0.156, and 0.226 (nM/μM) at Sts. 1, 2, and 3, respectively, and these values were much closer to the estimated regenerated ratio of Cd to PO₄ from the Apparent Oxygen Utilization (AOU)-Cd/PO₄ plots, which was 0.197 (nM/μM) in this study area. Below surface layers, the slopes of the Cd-PO₄ plot changed to 0.371, 0.352, and 0.362 (nM//μM) at Sts. 1, 2, and 3, respectively. In the relationships between Cd and PO₄, clear deviations or kinks were observed at three stations at a PO₄ concentration of approximately 0.2 μM in the plot, which was attributable to the discontinuity of surface water and the other layers across the North Pacific subtropical mode water. In studies of the interaction between surface water and biogenic particles concerning the Cd/PO₄ ratio, separate analyses of seawater (surface water and the other layers) should be carried out to obtain the individual surface water ratio because the Cd/PO₄ ratio in the surface water is expected to differ from that of the underlying water. Furthermore, the biological fractionation of these constituents is based on the surface water ratio. This revised version was published online in July 2006 with corrections to the Cover Date.     

A note on internal wavetrains and the associated undulation of the sea surface observed upstream of seamounts

An internal wavetrain, generated by a tidal current in superposition with the Tsushima Warm Current, has been observed by use of an acoustic echo-sounder upstream of the Shichiri-Ga-Sone Seamounts in the East Tsushima Strait of the Japan Sea. The sea surface above the internal wavetrain was simultaneously observed and was found to be undulated at the wavelength of the internal wave.     

Numerical calculation of free-surface potential flow around a ship using the modified Rankine source panel method

A modified Rankine source panel method is presented for solving a linearized free-surface flow problem with respect to the double-body potential. The method of solution is based on the distribution of Rankine sources on the hull as well as its image and on the free surface. An iterative algorithm is used for determining the free surface and wave resistance using upstream finite difference operator. A verification of numerical modeling is made using the Wigley hull and the validity of the computer program is examined by comparing the details of wave profiles and wave making resistance with Series 60 model.     

Fault induced permanent ground deformations: Experimental verification of wet and dry soil, numerical findings’ relation to field observations of tunnel damage and implications for design

Few building codes contains provisions fault surface ruptures and accompanying soil deformations which constitutes a great risk to human lives, buildings and infrastructure. A numerical and experimental comparison show a fair agreement of result. Analysis of “real” scale show the how water increases the incompressibility of wet soil causing shear deformations to become larger and conjugate ruptures to appear for reverse faults. Field observations and numerical analysis indicates that horizontal compression of soil surrounding underground structures should be taken into account in design.     

Numerical study of surface water circulation around Sekisei Lagoon, southwest Japan

This paper discusses the variability of surface currents around Sekisei Lagoon using a nested grid ocean circulation model. We developed a triple-nested grid system that consists of a coarse-resolution (1/60° or ∼1.85 km) model off Taiwan, an intermediate-resolution (1/300° or ∼370 m) model around the Yaeyama Islands, and a fine-resolution (1/900° or ∼123 m) model of Sekisei Lagoon. The nested grid system was forced by wind and heat flux calculated from six-hourly atmospheric reanalysis data and integrated over the period from May to July 2003. The coarse-resolution model was driven by lateral boundary conditions calculated from daily ocean reanalysis data to include realistic variation of the Kuroshio and mesoscale eddies with spatial scales of ∼500–700 km in the open ocean. The tidal forcing was included in the intermediate-resolution model by interpolating sea level data obtained from a data-assimilative tidal model. The results were then used to drive the fine-resolution model to simulate the surface water circulation around Sekisei lagoon. Model results show that (1) currents inside the lagoon are mainly driven by tide and wind; (2) there exists a strong southwestward current along the bottom slope in the southeast portion of the lagoon; the current is mainly driven by remote mesoscale eddies and at times intensified by the local wind; (3) the flow relaxation scheme is effective in reducing biases along the open boundaries. The simulated currents were used to examine the retention and dispersion of passive particles in the surface layer. Results show that the surface dispersion in the strong open ocean current region is significantly higher than that inside the lagoon.     

Glacio-geophysical implication of an NNSS positioning in and around Syowa Station, East Antarctica

Utilization of the two-wave NNSS receiver drastically improved the positioning accuracy on the ice sheet of Antarctica. The NNSS positioning gives us 3 m three-dimensional convergence with 25 accepted satellite passes, and is most useful for the measurement of ice flow velocity. The flow velocity vectors along Route S-H-Z on Mizuho plateau, East Antarctica were obtained by estimating positional change of glaciological traverse stations after 7 years' interval. The transformation of the coordinate system was necessary before the comparison of the positioning in 1973 by the geodetic traverse method on the Bessel Reference Ellipsoid with that in 1980 by the satellite Doppler method on the NWL-8E Ellipsoid. NNSS receiving experiments at astronomical datum point in Syowa Station enabled us to estimate the translation of the coordinate origin of the Bessel Reference Ellipsoid against the geocentric NWL-8E Ellipsoid and correction terms for coordinate transformation. The obtained flow velocity is 15 m/a at H17 of around 1000 m a.s.l. and 70 m/a at Z2 of around 2000 m a.s.l. with ±6% uncertainty, and is too large to be explained only by the laminar flow of the ice sheet. The obtained velocity vectors are found to be mostly parallel to the maximum slope of the free-air gravity anomaly contours and can be interpreted as the ice sheet sliding down the slope of the subglacial mound of 2400 m relative height from the average subglacial bedrock topography. If such bedrock sliding occurrs over the whole region of Mizuho Plateau, the related thinning of the ice sheet may be detected by the precise measurement of the height change of the same marker station. By dynamically modelling the ice sheet and substituting the observed parameters such as precipitation, principal strain rate, etc., into the equation of ice thickness change the submergence velocity of around −1 m/a is expected and will be detected by carefully designed repetitive NNSS receiving experiments after several year's interval.     

Subgrade model for transient response analysis of multiple embedded bodies

During the dynamic response of multiple partially or fully embedded structures, the subgrade medium at the sides of the structures not only generates the soil-structure interaction forces but also transmits the motions from one structural body to others. With Winkler's hypothesis, these forces and motions are formulated in the time-domain in a simple form utilizing the frequency-domains formulations. The validity of the developed formulations is examined using small-scale-model test results obtained for piles in a synthetic ground. A numerical example is provided to demonstrate the approach proposed and the formulations developed. The simplified time-domain formulations are found to be numerically efficient and yet capable of predicting the behaviour reasonably well.     

The Miduk porphyry Cu deposit,Kerman, Iran: A geochemical analysis of the potassic zone including halogen element systematics related to Cu mineralization processes

Miduk hypogene and supergene porphyry Cu–Mo mineralization occurs within the Miocene porphyritic quartz–diorite and host Eocene plagioclase–hornblende phyric andesitic pyroclastic and flow sequence. Both the host rocks were extensively altered by hydrothermal fluids to dominantly potassic, phyllic, and argillic with interstitial to distal propylitic types.