Stokes' expansion of internal deep water waves to the fifth order

Stokes' expansion is applied to the internal waves of finite amplitude, which propagate on the interface between two layers of infinite thickness. Stream function, wave profile, phase velocity and mass transport velocity are given in the fifth order approximation. It is shown that (a) phase velocity increases with increase of wave steepness, (b) mass transport appears in the direction of the wave propagation in both layers as in the case of the surface waves, and (c) when the density difference is very small, the wave profile is flattened not only at the troughs but also at the crests.     

Testing of a towed CTD

The results of laboratory and field experiments on a CTD measuring unit attached to a controllable towed body is described. It was verified that the three-dimensional distribution of salinity and temperature could be observed with sufficient accuracy (to 0.03 in salinity and to 0.01°C in temperature if proper correction is adopted) while cruising at up to 4 knots. A double integrated A/D converter is used to compensate for effects of extraneous environmental changes.     

Gas hydrate saturation at Site C0002, IODP Expeditions 314 and 315, in the Kumano Basin,Nankai trough

The degree of gas hydrate saturation at Integrated Ocean Drilling Program (IODP) Site C0002 in the Kumano Basin, Nankai Trough, was estimated from logging‐while‐drilling logs and core samples obtained during IODP Expeditions 314 and 315. Sediment porosity data necessary for the calculation of saturation were obtained from both core samples and density logs. Two forms of the Archie equation (‘quick‐look’ and ‘standard’) were used to calculate gas hydrate saturation from two types of electrical resistivity log data (ring resistivity and bit resistivity), and a three‐phase Biot‐type equation was used to calculate gas hydrate saturation from P‐wave velocity log data. The gas hydrate saturation baseline calculated from both resistivity logs ranges from 0% to 35%, and that calculated from the P‐wave velocity log ranges from 0% to 30%. High levels of gas hydrate saturation (>60%) are present as spikes in the ring resistivity log and correspond to the presence of gas hydrate concentrations within sandy layers. At several depths, saturation values obtained from P‐wave velocity data are lower than those obtained from bit resistivity data; this discrepancy is related to the presence of free gas at these depths. Previous research has suggested that gas from deep levels in the Kumano Basin has migrated up‐dip towards the southern and seaward edge of the basin near Site C0002. The high saturation values and presence of free gas at site C0002 suggest that a large gas flux is flowing to the southern and seaward edge of the basin from a deeper and/or more landward part of the Kumano Basin, with the southern edge of the Kumano Basin (the location of site C0002) being the main area of fluid accumulation.     

Traditional Irrigation Management in Betmera-Hiwane, Ethiopia： The Main Peculiarities for the Persistence of Irrigation Practices

Introduction Tigray, the northern region of Ethiopia (Figure 1), is located between 12°20′~14°30′N and 36° ~ 41°30′E. It is dominated by undulating topo- graphy with many mountains, plateaus, hills, depressions and limited flat lands. The elevation     

230Th/234U and 14C dating of a lowstand coral reef beneath the insular shelf off Irabu Island, Ryukyus, southwestern Japan

Abstract   High-resolution seismic reflection profiles delineated the distribution of mound-shaped reflections, which were interpreted as reefs, beneath the insular shelf western off Irabu Island, Ryukyus, southwestern Japan. A sediment core through one of the mounded structures was recovered from the sea floor at a depth of −118.2 m by offshore drilling and was dated by radiometric methods. The lithology and coral fauna of the core indicate that the mounded structure was composed of coral–algal boundstone suggesting a small-scaled coral reef. High-precision α-spectrometric ²³⁰Th/²³⁴U dating coupled with calibrated accelerator mass spectrometric ¹⁴C ages of corals obtained reliable ages of this reef ranging from 22.18 ± 0.63 to 30.47 ± 0.98 ka. This proves that such a submerged reef was formed during the lowstand stage of marine oxygen isotope stages 3–2. The existence of low-Mg calcite in the aragonitic coral skeleton of 22.18 ± 0.63 ka provides evidence that the reef had once been exposed by lowering of the relative sealevel to at least −126 m during the last glacial maximum in the study area. There is no room for doubt that a coral reef grew during the last glacial period on the shelf off Irabu Island of Ryukyus in the subtropical region of western Pacific.     

Annual Variability of Sea Surface Height and Upper Layer Thickness in the Pacific Ocean

The annual variabilities of the sea surface height in the Pacific Ocean were investigated by analyzing the TOPEX/POSEIDON satellite data and by solving a reduced gravity model. We discuss how adequately the simple model can capture the variabilities of the sea surface height, and what the cause of the variabilities is. Three large amplitude peaks in the satellite data are found along the 12°N longitude line. Two elongated zones with a large amplitude are also found: one extends east-west along 6°N and the other extends northwestward from South America around 25°S. These features are adequately reproduced in the numerical simulation of the reduced gravity model. The propagation of the Rossby wave is analyzed by the use of the extended Eliassen-Palm flux to investigate the mechanism of these annual variabilities. The two east peaks around 12°N can be explained in terms of the interference between the local Ekman pumping and the free wave emitted near the western coast of North America, and the most western peak is affected by the Rossby wave formed by the local wind stress. The elongated zonal area around 6°N is mainly due to the local Ekman pumping. Another area around 25°S results from the convergence of the free Rossby wave emitted from the eastern boundary and the area with the strong wind stress curl off South America. A discrepancy between the satellite data and the model results suggests that the eastern equatorial Pacific Ocean is relatively calm in the model but not in the satellite data. This revised version was published online in July 2006 with corrections to the Cover Date.     

Vertical distribution of bacterial abundance in the northwest pacific ocean

Mixed populations of free-living marine bacteria were collected at depths from the surface to the bottom (1,960m in Suruga Bay and 1,585 m in the Japan Sea) in the northwest Pacific during deep-sea diving by the submersible,Shinkai 2000. Their abundance in total cell counts and in lipopolysaccharide (LPS) concentration was found to decrease with increasing depth, and the decreasing profiles were shown to be linear on logarithmic scales. The total cell counts and the LPS concentration showed a linear relationship on arithmetic scales, and the LPS content per cell was found to be 1.02×10^–14 g.     

Molecules of Non-Photospheric Origin in Red Giants and Supergiants Revealed by the ISO SWS

Overall SEDs based on ISO SWS observations show fair agreement with photospheric model predictions for red (super)giant stars. However, some details of molecular spectra cannot be explained by a photospheric origin. In particular, fine structure in the H2O 2.7 μm band can be clearly resolved by the SWS and is identified in an early M giant, whose photosphere will never produce H2O. This is definite evidence for H2O of non-photospheric origin in an early M giant. Also, the observed H2O and CO2 bands in a late M giant are too strong to be explained by a photospheric origin alone. Further, the H2O 2.7 μm band is found in four early M supergiants in the h + χ Persei clusters (three of which show UIRs) and is especially strong in the M4 supergiant S Per (which also shows a highly peculiar SED). Thus, against a belief that H2O is found only in the latest M giants such as Miras, the SWS has revealed the presence of H2O in a wider region of the HR diagram. The origin of this H2O is unknown but is probably in a non-photospheric extra envelope. Such a H2O envelope appears to be a general feature through early M (super)giants to cool supergiants such as S Per, where the envelope has finally developed to be optically thick. This revised version was published online in August 2006 with corrections to the Cover Date.