Interannual Sea Level Variations and Annual Tides in the Northwestern Pacific

Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone.     

Paleoenvironmental analysis of the Mawaki archaeological site,central Japan,in relation to the stratigraphic position of dolphin bones

In order to elucidate the paleoenvironment associated with the early Holocene Mawaki archaeological site on the Noto Peninsula of central Japan, a high‐resolution stratigraphic study was conducted of 17 boreholes drilled at the archaeological site. We selected three boreholes for which lithological and/or chronological data are reported. Initial magnetic susceptibility was utilized for correlation of clastic core samples with the assistance of 26 radiocarbon dates. Four lithological units (A, B, C, and D in ascending order) were identified and interpreted as a sequence in a cycle of marine transgression and regression. Dated coastal horizons were chosen to indicate former sea levels. A Holocene relative sea level curve was generated on the basis of the geological data, and a rapid rise from 8000cal. yr B.P. to 7000cal. yr B.P. and a succeeding minor sea level fall represent the basic eustatic trend around the Sea of Japan because hydroisostatic and tectonic effects are moderate in the study area. Abundant dolphin bones lay just above the top of the marine sequence (boundary between Units C and D), located in the seashore environment. Cultural artifacts are found in a subaerial deposit (Unit D) near the dolphin bone level that is assigned to a period of high, stable sea level after the post‐glacial eustatic highstand. Dolphin bones are associated with stone artifacts (arrowheads, knives, and scrapers) and ritual wood columns, indicating the presence of a longstanding fishery during the early Holocene on the Sea of Japan coast. © 2011 Wiley Periodicals, Inc.     

Kinetics of decompressional reactions in eclogitic rocks – formation of plagioclase coronas around kyanite

This paper describes a kinetic study on reaction textures in eclogitic rocks from the Sulu region, eastern China. Some of the eclogitic rocks display a decompressional reaction texture, whereby kyanite grains are surrounded by plagioclase coronas and are never in contact with quartz. The change in mineral parageneses with progress of the reaction was predicted by constructing chemical potential diagrams in a model system. The chemical potential diagrams indicated that the chemical potential of 2Na₂O + CaO (2µ_Na2O + µ_CaO) in intergranular regions between kyanite and quartz should decrease with decreasing pressure, whereas 2µ_Na2O + µ_CaO in intergranular regions between garnet and omphacite should increase with decreasing pressure. Thus, upon decompression, an inequality in chemical potential arises in the rock. To reduce this inequality, garnet and omphacite react to produce amphibole and plagioclase and release Na₂O and CaO. Then, the released Na₂O and CaO components diffuse into the regions between kyanite and quartz grains and react to produce plagioclase between them. This model also indicates that the chemical potential of SiO₂ should decrease around kyanite grains during the progress of the decompressional reaction, and Si‐undersaturated conditions should have formed around kyanite grains in spite of the presence of quartz in these eclogitic rocks. Thus, spinel or corundum that are not stable in the system with excess quartz can form as a metastable phase, as observed in eclogitic rocks from the study areas. Phase diagrams in the system with excess quartz should be carefully applied for analysis of such reaction textures.     

Plasmaspheric hiss observed in the topside ionosphere at mid- and low-latitudes

Latitudinal characteristics of ELF hiss in mid- and low-latitudes have been statistically studied by using ELF/VLF electric field spectra (50 Hz-30 kHz) from ISIS-1 and -2 received at Kashima station, Japan from 1973 to 1977. Most ISIS ELF/VLF data observed in mid- and low-latitude include ELF hiss at frequencies below a few kHz. The ELF hiss has the strongest intensity among VLF phenomena observed by the ISIS electric dipole antenna in mid- and low-latitudes, but the ELF hiss has no rising structure like the chorus in the detailed frequency-time spectrum. The ELF hiss is classified into the steady ELF hiss whose upper frequency limit is approximately constant with latitude and the ELF hiss whose upper frequency limit increases with latitude. These two types of ELF hiss occur often in medium or quiet geomagnetic activities. Sometimes there occurs a partial or complete lack of ELF hiss along an ISIS pass.Spectral shape and bandwidth of ELF hiss in the topside ionosphere are very similar to those of plasmaspheric hiss and of inner zone hiss. The occurrence rate of steady ELF hiss is about 0.3 near the geomagnetic equator and decreases rapidly with latitude around L = 3. Hence it seems likely that ELF hiss is generated by cyclotron resonant instability with electrons of several tens of keV in the equatorial outer plasmasphere beyond L = 3.Thirty-seven per cent of ELF hiss events received at Kashima station occurred during storm times and 63% of them occurred in non-storm or quiet periods. Sixty-seven per cent of 82 ELF hiss events during storm times were observed in the recovery phase of geomagnetic storms. This agrees with the previous satellite observations of ELF hiss by search coil magnetometers. The electric field of ELF hiss becomes very weak every 10 s, which is the satellite spin period, in mid- and low-latitudes, but not near the geomagnetic equator. Ray tracing results suggest that waves of ELF hiss generated in the equatorial outer plasmasphere propagate down in the electrostatic whistler mode towards the equatorial ionosphere, bouncing between the LHR reflection points in both the plasmaspheric hemispheres.     

Hill stability of the planar three-body problem: General and restricted cases

The equations of motion of the planar three-body problem split into two parts, called an external part and an internal part. When the third mass approaches zero, the first part tends to the equations of the Kepler motion of the primaries and the second part to the equations of motion of the restricted problem.We discuss the Hill stability from these equations of motion and the energy integral. In particular, the Jacobi integral for the circular restricted problem is seen as an infinitesimal-mass-order term of the Sundman function in this context.     

The gravity-darkening of highly distorted stars in close binary systems

From a quantitative analysis of the photometric ellipticity effect, values of the exponent of gravity-darkening have been empirically deduced for the components of sixteen W UMa systems with accurate cross-correlation spectroscopic mass ratios. In the analysis, the exponents for both components of a W UMa system are assumed to be the same. In view of the generally unstable nature of their light curves and the consequent difficulty to find an unique set of the fractional radii of both components, -values have been derived for various equipotential surfaces with boundary cases set at the inner and outer Roche lobes.The results indicate that if the fill-out factors are less than 0.5 (as is so for most of the actual cases), the deduced -values are all greater than Lucy's conventional value of 0.32. The empirical -values as a whole are found to increase with the mean effective temperature of the components and, furthermore, they show a tendency to decrease with increasing mass ratio, particularly for A-type systems. Thus, a W UMa system consisting of two components of quite different masses has a large empirical -value. These observational evidences indicate that the structure of the photosphere of contact components of W UMa systems is significantly different from that of normal Main-Sequence stars of similar spectral type and may provide a clue to solve puzzles of W UMa stars.     

Global sounding of sporadic E layers by the GPS/MET radio occultation experiment

The GPS radio occultation technique is sensitive for layered structures with horizontal scales of around 100 km and with vertical scales of a few 100 m or more at the Earth's limb. These structures cause strong fluctuations of the GPS L1 and L2 phase paths which have been measured by a GPS receiver onboard of Microlab-1 satellite in 730 km orbit during the GPS/Meteorology experiment (GPS/MET of UCAR, Boulder). By means of GPS/MET radio occultation data, profiles of electron density fluctuations are derived for the mesosphere/lower thermosphere region with a height resolution of around 1 km. Data analysis of 1900 radio occultation events in June/July 1995, 1540 events in October 1995, and 2690 events in February 1997 confirms seasonal dependence of sporadic E layers. The meridian slices of average sporadic E activity show a dominance of plasma irregularities in the summer hemisphere. The irregularities mainly occur at heights 90–110 km. Auroral and equatorial sporadic E, electron density depletions, and multiple ionization layers are also present in the high resolution GPS/MET data. The multiple layers often have a distance of around 5–10 km in height, and appear up to a height of 140 km (upper height limit for 50 Hz sampling rate of GPS receiver). For February and June, the GPS/MET observations are compared to ground-based observations of the Asia/Australia ionosonde chain.     

Growth characteristics ofChattonella antiqua

Nutrient requirements of a red tide flagellate,Chattonella antiqua, were investigated in a laboratory culture experiment. Growth ofC. antiqua was supported by nitrate and ammonium, and by urea to a limited extent, but not by glycine, alanine and glutamate. Orthophosphate served as a good phosphorus source but glycerophosphate did not. Fe³⁺ (1µM) fully promoted the flagellate's growth in the presence of 80µM of EDTA. The addition of Mn²⁺ (0–20µM), Zn²⁺ (0–10µM) and Co²⁺ (0–0.4µM) did not show any effect. Among three vitamins tested, only B₁₂ (6 ng 1^?1) served as a growth factor. Glucose, acetate and glycolate did not improve growth in the light nor did they support growth in darkness. The minimum cell quotas for nitrogen, phosphorus, iron and B₁₂ were estimated to be 11 pmoles ce^?1, 1.0, ～0.09 and 1.1 fg cell^?1, respectively.     

Dispersion and accumulation of radionuclides in sediment of Urazoko Bay (I)

Contents of⁹⁰Sr,¹³⁷Cs and⁶⁰Co in surface sediments were investigated in and around Urazoko Bay, Fukui Prefecture, where a nuclear power plant has been operating since 1969 and the waste effluent has been released into the sea. The main source of⁹⁰Sr and¹³⁷Cs was recognized to be radioactive fallout, whereas⁶⁰Co was considered to originate from the nuclear power plant. Using the¹³⁷Cs concentration as an indicator of sorption capacity of the sediment, the behaviour of⁶⁰Co was investigated. No seasonal variation was observed in the distribution pattern of⁶⁰Co/¹³⁷Cs ratio and the retention of the heavy initial discharge in 1969 was considered to dominate the radionuclide level in the sediment. Correlation of⁶⁰Co/¹³⁷Cs ratio in the sediment and the distance from the discharge outlet was expressed by a simple exponential function of the distance. It was suggested that the contamination is spreading out gradually to the outer region of Urazoko Bay.     

Chemical environment for red tides due toChattonella antiqua

In order to assess the roles of Fe and Cu in outbreaks ofChattonella antiqua red tide, concentrations of these metals in the surface seawater were monitored around the Ie-shima Islands in the Seto Inland Sea during the summers of 1986–1988. Bioassay of the surface seawater with respect to Fe and Cu was also conducted using a cultured strain ofC. antiqua.Concentrations of Fe and Cu in the filtered seawater (Fe^F and Cu^F) were in the range of 3.9–10.0 and 9.3–11.2 nM, respectively. The bioassay with respect to Fe revealed that Fe at the surface layer was usually insufficient to support the maximum growth rate ofC. antiqua, except whenC. antiqua was dominant in the field. However, correlations between Fe^F and the growth rate of the control cultures (Fe, EDTA=not enriched; N, P, B₁₂=enriched at optimum levels) were not apparent, probably because Fe^F did not reflect the concentration of available Fe.The bioassay with respect to Cu was coupled with the Cu^F values obtained. The results indicated that Cu at the surface layer was detoxified by complexation with natural organic ligand(s), and that pCu (=minus log of cupric ion activity) was 11.5–11.7, optimum for the growth ofC. antiqua, throughout the survey period. It is suggested that Fe, but not Cu, is a potentially important factor in regulating the natural populations ofC. antiqua in the Seto Inland Sea.