The latest batch-to-batch difference table of standard seawater and its application to the WOCE onetime sections

An updated batch-to-batch difference table of IAPSO standard seawater (SSW) up to P145 is proposed. The batch-to-batch difference table is based on several recent SSW comparison experiments, including the experiments conducted independently at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and Woods Hole Institute of Oceanography (WHOI) at about the same time using the same procedure. Proposed batch-to-batch differences range from 1.2 × 10⁻³ to −1.9 × 10⁻³ with reference to the average of those from P91 to P102. Batch-to-batch differences from P29 to P145 with reference to the recent batches and this average over every 5 years since 1960 are also presented, together with standard deviation. This reveals that inconsistency among batches has improved since 1980s. In particular, the standard deviation was 0.3 × 10⁻³ in this decade, which is about one-half the value reported previously and almost equal to the modern measurement precision (0.2 × 10⁻³) and is within-batch difference (<0.3 × 10⁻³). Proposed batch-to-batch differences were applied to the observational results of the WOCE hydrographic onetime section (WHP onetime) in the Indian Ocean. Average absolute salinity differences at 14 crossover points in the Indian Ocean were slightly larger, from 1.2 × 10⁻³ to 1.5 × 10⁻³, when the batch-to-batch difference table was applied; however, when results from the Indian, Pacific, and Atlantic Oceans were combined, application of the batch-to-batch difference table yielded statistically acceptable salinity differences. The table was also applied to WHP sections P1 and P17 (revisited about 10 years after the original observations during the WOCE period) and sections I1, I7, and I8 (visited twice by different research vessels in the same year). In all cases, the table corrected unrealistically large salinity changes in space and time. The results suggest that the application of the batch-to-batch table to well-controlled salinity data such as WOCE datasets would be effective in making the datasets more consistent in space and time.     

Partitioning of heavy metals into mineral and organic fractions in a sediment core sample from Osaka Bay

Partitioning of copper, zinc, iron and manganese into oxide, sulfide, organic and silicate fractions has been determined with a selective chemical leaching technique on sediment samples from a core collected in Osaka Bay. The samples have been dated by the²¹⁰Pb method. Most of the copper and zinc in the polluted surface sediment layer are contained in both oxide and sulfide fractions. This suggests that the transformation of oxides and hydroxides to sulfides under anoxic conditions within the sediment is significant for the fixation of copper and zinc discharged through human activities into the sediment. Manganese is apparently enriched in oxide and hydroxide fractions of the surface layer due to the post-depositional migration of manganese within the sediment. The copper, zinc and manganese contents of the 30 % H₂O₂ soluble fraction (mostly organic fraction) decrease with depth in the sediment core, and correlate significantly with the organic carbon content. The heavy metal (Cu, Zn, Fe and Mn) contents of the silicate fraction, without exchangeable sites, are almost constant with depth.     

Some regular patterns in the distribution of sediment contamination in the coastal waters along Japan

Observations of sediment contamination along the coast of Japan were analyzed. When the pollutant concentration is divided by the fine particle fraction in the sediment, a regular pattern is observed in the quantitative relationship among the degree and the area of contamination and the discharge rate of pollutant released continuously into the water along the coast. This regularity was observed with respect to COD,n-hexane soluble substances and heavy metals, and could be expressed by a formula.Polluted particles were supposed to disperse through suspension in the bottom water layer, and thus their distribution in the surface sediment is expected to become similar to effluent dispersion in the surface water.     

Unusual Behavior of the Kuroshio Current System from Winter 1996 to Summer 1997 Revealed by ADEOS-OCTS and Other Data (Continued): A Study from Broad External Conditions with Bottom Topography

In the previous paper (Toba and Murakami, 1998) we reported on an unusual path of the Kuroshio Current System, which occurred in April 1997 (April 1997 event), using the Ocean Color and Temperature Scanner (OCTS) data of the Advanced Earth Observing Satellite (ADEOS). The April 1997 event was characterized by the flow of the Kuroshio along the western slope (northward) and the eastern slope (southward) of the Izu-Ogasawara Ridge, a very southerly turning point at about 32°N, followed by a straight northward path up to 37°N of the Kuroshio Extension along the eastern flank of the Izu-Ogasawara and the Japan Trenches. Overlaying of depth contours on ADEOS-OCTS chlorophyll-a images at the April 1997 event demonstrates the bottom topography effects on the current paths. A new finding based on TOPEX/Poseidon altimeter data is that the sea-surface gradient across the Kuroshio/Kuroshio Extension diminished greatly in the sea area southeast of the central Japan, as a very temporary phenomenon prior to this event. This temporary diminishing of the upper-ocean current velocity might have caused a stronger bottom effect along the Izu-Ogasawara Ridge, and over the Izu-Ogasawara Trench disclosed a weak background, barotropic trench-flank current pattern, which existed otherwise independently of the Kuroshio Extension. The very southerly path of the Kuroshio Extension from winter 1996 to autumn 1998 corresponded, with a time lag of about 1.5 years, to the previous La Niña tendency with weaker North Equatorial Current. The April 1997 event occurred in accordance with its extreme condition.     

Spatio-temporal deposition profile of an experimentally produced turbidity current with a continuous suspension supply

A turbidity current is a turbulent, particle-laden gravity current that is driven by density differences resulting from the presence of suspended sediment particles. The current travels downslope, bearing a large amount of sediment over a great distance, and forms fluvial and submarine bedforms. Knowledge of the spatio-temporal deposition profile of turbidity-deposited sediment is important for a better understanding of sediment transport by turbidity currents. In the current study, the depositi...     

Seismic performance evaluation and risk assessment of typical reinforced concrete frame buildings with masonry infill and conventional vertical extension in Nepal

Bulletin of Earthquake Engineering - Many reinforced concrete (RC) frame buildings in Nepal were significantly damaged by the 7.8 magnitude (Mw) earthquake in Nepal on April 25, 2015. To contribute...     

Determination of reaction kinetics using grain size: An application for metamorphic zircon growth

The reaction kinetics of metamorphic minerals can be subdivided into interface‐ and diffusion‐controlled kinetics. The discrimination of reaction kinetics is crucial for estimating reaction rates. Here, we propose a new and simple method for discriminating reaction kinetics. This method requires measuring only the initial and final grain sizes during growth. The reaction kinetics is inferred from different plotted arrays of initial vs. final grain sizes after the mineral growth. Using metamorphic zircon, we take detrital core sizes as the initial sizes and post‐metamorphic grain sizes as the final sizes. The application of the method to the subduction‐related high‐pressure Nagasaki metamorphic complex in Japan shows that this metamorphic zircon grew under interface‐controlled kinetics even at the relatively low temperature of 440°C. This method is potentially applicable to other minerals that have time‐markers, such as chemical zoning or internal structures that are captured at a given point in time during growth.     

Vertical material flux under seasonal sea ice in the Okhotsk Sea north of Hokkaido, Japan

Downward material fluxes under seasonal sea ice were measured using a time-series sediment trap installed at an offshore site in the Okhotsk Sea north of Hokkaido, Japan, from 13 January to 23 March 2005. The maximum fluxes of lithogenic material (753 mg m⁻² day⁻¹) and organic matter (mainly detritus; 333 mg m⁻² day⁻¹) were recorded during the period in which sea ice drifted ashore and increased in extent, from 13 January to 9 February. Organic matter as fecal pellets (81–93 mg m⁻² day⁻¹) and opal as biosilica (51–67 mg m⁻² day⁻¹), representing diatom fluxes, were abundant in sediment trap samples obtained during the period of full sea ice coverage from 10 February to 9 March. Microscopic observations revealed that fecal pellets were largely diatom frustules, suggesting that zooplankton actively grazed on ice algae during the period of full sea ice coverage. During the period of retreating sea ice, from 10 to 23 March, the phytoplankton flux showed a rapid increase (from 9.5 to 22.5 × 10⁶ cells m⁻² day⁻¹), reflecting their release into the water column as the sea ice melted. Our results demonstrate that the quantity and quality of sinking biogenic and lithogenic materials vary with the seasonal extent of sea ice in mid-winter.     

Finite-element simulations of long-period ground motions: Japanese subduction-zone earthquakes and the 1906 San Francisco earthquake

Large earthquakes at shallow depths commonly excite long-period ground motions in distant sedimentary basins, thereby inflicting damage upon large-scale structures. For example, the 2003 Tokachi-oki earthquake, Japan, damaged oil tanks in the Yufutsu Basin, located 250 km from the epicenter. Similar long-range effects were also observed during the 2004 earthquake off Kii Peninsula, Japan. In this study, we present the results of simulations of these earthquakes undertaken using the finite element method (FEM) with a voxel mesh. In addition, to examine whether the 1906 San Francisco earthquake excited long-period ground motions in the Los Angeles-area basins, we performed long-period ground motion simulations of most of the California region. The FEM simulations confirmed the importance of path effects for the development of long-period ground motions.     

RXTE observation of NGC 6240: a search for the obscured active nucleus

We present new data taken at 850 μm with SCUBA at the James Clerk Maxwell Telescope for a sample of 19 luminous infrared galaxies. Fourteen galaxies were detected. We have used these data, together with fluxes at 25, 60 and 100 μm from IRAS , to model the dust emission. We find that the emission from most galaxies can be described by an optically thin, single temperature dust model with an exponent of the dust extinction coefficient ( k _λ ∝ λ ^{− β} ) of β ≃1.4–2. A lower β ≃1 is required to model the dust emission from two of the galaxies, Arp 220 and NGC 4418. We discuss various possibilities for this difference and conclude that the most likely is a high dust opacity. In addition, we compare the molecular gas mass derived from the dust emission, M _850 μm, with the molecular gas mass derived from the CO emission, M _CO, and find that M _CO is on average a factor 2–3 higher than M _850 μm.