Isotope fractionation of neon during stepheating extraction?: a comment on ‘Re‐interpretation of the existence of a primitive plume under Australia based on neon isotope fractionation during step heating’ by Gautheron and Moreira (2003)     

Takuya Matsumoto  Masahiko Honda  Ian McDougall  Igor Yatsevich  Suzanne Y. O'Reilly 《地学学报》2004,16(1):23-26

Using a Rayleigh distillation fractionation model, we calculate that the maximum isotope fractionation potentially achievable is less than 5% during the early stages of gas release from a sample. Our calculation corrects the erroneous conclusions of Gautheron and Moreira (2003), who re‐interpreted the plume‐like neon isotopic compositions found in metasomatic apatite from a south‐eastern Australian xenolith (Matsumoto et al., 1997) to be the result of Rayleigh‐type isotope fractionation of originally MORB‐type neon during stepheating gas extraction. We stress that the modelling of neon isotopic fractionation by Gautheron and Moreira (2003) is incorrect, and that the finding of a plume‐like neon isotopic composition in the apatite by Matsumoto et al. (1997) remains a quite valid and robust conclusion.  相似文献   

Real-time difference imaging analysis of MOA Galactic bulge observations during 2000     

I.A. Bond  F. Abe  R.J. Dodd  J.B. Hearnshaw  M. Honda  J. Jugaku  P.M. Kilmartin  A. Marles  K. Masuda  Y. Matsubara  Y. Muraki  T. Nakamura  G. Nankivell  S. Noda  C. Noguchi  K. Ohnishi  N.J. Rattenbury  M. Reid  To. Saito  H. Sato  M. Sekiguchi  J. Skuljan  D.J. Sullivan  T. Sumi  M. Takeuti  Y. Watase  S. Wilkinson  R. Yamada  T. Yanagisawa  P.C.M. Yock 《Monthly notices of the Royal Astronomical Society》2001,327(3):868-880

We describe observations carried out by the MOA group of the Galactic bulge during 2000 that were designed to detect efficiently gravitational microlensing of faint stars in which the magnification is high and/or of short duration. These events are particularly useful for studies of extrasolar planets and faint stars. Approximately 17 deg² were monitored at a sampling rate of up to six times per night. The images were analysed in real time using a difference imaging technique. 20 microlensing candidates were detected, of which eight were alerted to the microlensing community whilst in progress. Approximately half of the candidates had high magnifications (≳10), at least one had very high magnification (≳50), and one exhibited a clear parallax effect. The details of these events are reported here, together with details of the on-line difference imaging technique. Some nova-like events were also observed and these are described, together with one asteroid.  相似文献   

Near inertial motion excited by wind change in a margin of the Typhoon 9019   总被引：1，自引：0，他引：1  

Akio Maeda  Kazuki Uejima  Toru Yamashiro  Masahito Sakurai  Hiroshi Ichikawa  Masaki Chaen  Keisuke Taira  Shinjirou Mizuno 《Journal of Oceanography》1996,52(3):375-388

An excitation of inertial oscillation in the upper layer east of course of Typhoon 9019 was fortuitously observed at three surface buoys deployed during the Ocean Mixed Layer Experiment (OMLET). The observed inertial oscillation was compared with wind fluctuation measured at Ocean Weather Station T (29°N, 135°E) which was placed at the center of a triangle with three vertexes occupied by the respective surface buoys. Inertial oscillation is effectively excited in the mixed layer at the eastern margin of the typhoon by a rapid decrease of wind rather than by prevailing strong wind. It is shown by means of a least square deviation that the inertial oscillation observed in the mixed layer has a period of 23.9 hours shorter than the local inertial period of 24.7 hours. This shorter period suggests that the inertial oscillation has the finite velocities of phase and group as an inertial internal wave. A theoretically obtained ratio of vertical component of group velocity to that of phase velocity, approximately agrees with observed value. The inertial internal wave is excited by fluctuation of divergence with near inertial period in the mixed layer.  相似文献   

Excess CO2 and pHexcess in the Intermediate Water Layer of the Northwestern Pacific     

Andrey Andreev  Makio Honda  Yuichiro Kumamoto  Masashi Kusakabe  Akihiko Murata 《Journal of Oceanography》2001,57(2):177-188

Excess CO₂ and pH_excess showing an increase in dissolved inorganic carbon and a decrease in pH from the beginning of the industrial epoch (middle of the 19th century) until the present time have been calculated in the intermediate water layer of the northwestern Pacific and the Okhotsk Sea. It is concluded that: (1) The Kuril Basin (Okhotsk Sea) and the Bussol' Strait areas are characterized by the greatest concentrations of excess CO₂ at isopycnal surfaces due to the processes of formation and transformation of intermediate water mass. (2) The largest difference in excess CO₂ concentration between the Okhotsk Sea and the western subarctic Pacific (about 8 µmol/kg) is found at the = 27.0. (3) The difference in excess CO₂ between the western subarctic Pacific and subtropical regions is significant only in the upper part of the intermediate water layer ( = 26.7–27.0). (4) About 10% of the excess CO₂ accumulation in the subtropical north Pacific is determined by water exchange with the subarctic Pacific and the Okhotsk Sea.  相似文献   

Nankai Trough: A hot trench?     

M. Yamano  S. Honda  S. Uyeda 《Marine Geophysical Researches》1984,6(2):187-203

Heat flow estimated from the gas hydrate layers on the landward slope of the Nankai Trough reveals that heat flow increases downslope toward the trench floor. This data plus six new heat flow values obtained by a conventional probe and two values available from DSDP drill holes give a fairly detailed heat flow distribution in the Nankai Trough area, when combined with the already existing data set. There appears to be a zonal pattern parallel to the trough axis, with a high heat flow zone on the floor of the trough that is quite anomalous for a subduction zone. It might be explained as a result of subduction of the hot portion of the Philippine Sea plate, i.e. the Shikoku Basin, and/or of more local effects such as heating due to intrusion of hot water from subducted sediments to shallow depth beneath the trough floor. Surface heat flow patterns landward of the trough were calculated for a simple thermal model of subduction. Perfect reproduction of the observed zonal pattern is difficult to achieve by the simple model, suggesting the necessity for further heat flow and other observations.  相似文献   

Correction method for full-depth current velocity with lowered acoustic Doppler current profiler (LADCP)   总被引：1，自引：0，他引：1  

Kanae Komaki  Masaki Kawabe 《Journal of Oceanography》2007,63(6):995-1007

A new method is presented to process and correct full-depth current velocity data obtained from a lowered acoustic Doppler current profiler (LADCP). The analysis shows that, except near the surface, the echo intensity of a reflected sound pulse is closely correlated with the magnitude of the difference in vertical shear of velocity between downcast and upcast, indicating an error in velocity shear. The present method features the use of echo intensity for the correction of velocity shear. The correction values are determined as to fit LADCP velocity to shipboard ADCP (SADCP) and LADCP bottom-tracked velocities. The method is as follows. Initially, a profile of velocity relative to the sea surface is obtained by integrating vertical shears of velocity after low-quality data are rejected. Second, the relative velocity is fitted to the velocity at 100–800 dbar measured by SADCP to obtain an “absolute” velocity profile. Third, the velocity shear is corrected using the relationship between the errors in velocity shears and echo intensity, in order to adjust the velocity at sea bottom to the bottom-tracked velocity measured by LADCP. Finally, the velocity profile is obtained from the SADCP-fitted velocity at depths less than 800 dbar and the corrected velocity shear at depths greater than 800 dbar. This method is valid for a full-depth LADCP cast throughout which the echo intensity is relatively high (greater than 75 dB in the present analysis). Although the processed velocity may include errors of 1–2 cm s⁻¹, this method produced qualitatively good current structures in the Northeast Pacific Basin that were consistent with the deep current structures inferred from silicate distribution, and the averaged velocities were significantly different from those calculated by the Visbeck (2002) method.  相似文献   

Variations of the Kuroshio Axis South of Kyushu in Relation to the Large Meander of the Kuroshio   总被引：1，自引：0，他引：1  

Toru Yamashiro  Masaki Kawabe 《Journal of Oceanography》2002,58(3):487-503

The characteristics of the Kuroshio axis south of Kyushu, which meanders almost sinusoidally, are clarified in relation to the large meander of the Kuroshio by analyzing water temperature data during 1961–95 and sea level during 1984–95. The shape of the Kuroshio axis south of Kyushu is classified into three categories of small, medium, and large amplitude of meander. The small amplitude category occupies more than a half of the large-meander (LM) period, while the medium amplitude category takes up more than a half of the non-large-meander (NLM) period. Therefore, the amplitude and, in turn, the curvature of the Kuroshio axis is smaller on average during the LM period than the NLM period. The mean Kuroshio axis during the LM period is located farther north at every longitude south of Kyushu than during the NLM period, with a slight difference west of the Tokara Islands and a large difference to the east. A northward shift of the Kuroshio axis in particular east of the Tokara Islands induces small amplitude and curvature of the meandering shape during the LM period. During the NLM period, the meandering shape and position south of Kyushu change little with Kuroshio volume transport. In the LM formation stage, the variation of the Kuroshio axis is small west of the Tokara Islands but large to the east due to a small meander of the Kuroshio. In the LM decay stage, the Kuroshio meanders greatly south of Kyushu and is located stably near the coast southeast of Kyushu. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Sea level variations around the Nansei Islands and the large meander in the Kuroshio south of central Japan     

Masaki Kawabe 《Journal of Oceanography》1980,36(4):227-235

The sea level difference between Naze and Nishinoomote and sea level anomalies (the residuals after removal of seasonal variations) around the Nansei Islands were examined in relation to the large meander in the Kuroshio south of central Japan. They are indices of surface velocity and geostrophic transport of the Kuroshio in the Tokara Strait and in the East China Sea, respectively. All of them were large during the meandering period, and each of them reached a maximum before or after the generation of the large meander in 1975. Thus the surface velocity and the geostrophic transport of the Kuroshio in the Tokara Strait and the East China Sea were large during the meandering period. The sea level difference between Naze and Nishinoomote (or Makurazaki) shows that the surface velocity and geostrophic transport in the Tokara Strait were significantly larger during the extinction stage in 1963 and during the generation stage in 1975 and were correlated with the position of the Kuroshio east of Kyûshû in 1974 and 1975 before the generation of the large meander.The surface velocity of the Kuroshio southeast of Yakushima (E-line) based on dynamic calculation referred to 1,000 db was weak during the meandering period, and was out of phase with the variation of surface velocity in the Tokara Strait monitored by tide gauge data. The analysis of GEK and hydrographic data shows that southwestward flow existed below 600 m in the slope region on the E-line and weakened during the meandering period. Thus, the out-of-phase variation in surface velocity mentioned above seems to be partly explained by the variation in velocity on the reference level at the E-line.  相似文献   

Coastal trapped waves in a two-layer ocean: Wave properties when the density interface intersects a sloping bottom     

Masaki Kawabe 《Journal of Oceanography》1982,38(3):115-124

Properties of coastal trapped waves when the pycnocline intersects a sloping bottom are studied using a two-layer model which has slopes in both layers. In this system there is an infinite discrete sequence of modes, and four different sorts of waves exist: the barotropic Kelvin wave, the upper shelf wave, the lower shelf wave and the internal Kelvin-type wave. They all propagate with the coast to their right in the Northern Hemisphere. The upper and lower shelf waves are due to the topographic-effect on the upper-layer and lower-layer slopes, respectively. Their motions are dominant in the respective layers being accompanied by significant interface elevations. The properties of the upper (lower) shelf wave are almost unaffected by the existence of a lower-layer (upper-layer) slope. The motion of the internal Kelvin-type wave is confined to the region around the line where the density interface intersects the bottom slope.The modes, except that with the fastest phase speed (the barotropic Kelvin wave), are assigned mode numbers in order of descending frequency. Characteristics of Mode 1 change with wavenumber; the upper shelf wave for small wavenumbers and the internal Kelvin-type wave for large wavenumbers (high frequencies). The higher modes of Mode 2 and above can be classified into the upper and lower shelf waves.  相似文献   

Sea level variations along the south coast of Japan and the large meander in the Kuroshio     

Masaki Kawabe 《Journal of Oceanography》1980,36(2):97-104

Sea level variations from 1974 through 1976 at 9 stations on the south coast of Japan (from west to east, Aburatsu, Tosa-shimizu, Muroto-misaki, Kushimoto, Uragami, Owase, Toba, Maisaka and Omaezaki) were analysed in relation to the large meander in the Kuroshio. From May to July in 1975, a small maximum in sea level variation was observed at every station west of Cape Shionomisaki from Aburatsu to Kushimoto. It propagated eastward along with the eastward propagation of a small meander in the Kuroshio until it reached Kushimoto, when the sea levels at Uragami and Owase started to rise sharply. This remarkable rise appeared at all stations in August when a large meander in the Kuroshio was established. The mean sea level at the stations east of Cape Shionomisaki from Uragami to Omaezaki rose by about 10 cm. The difference in sea level variations between the regions east and west of Cape Shionomisaki, which had been present before the rise, disappeared. A similar characteristic of sea level variation was also found in the generation stage of the large meander in 1959. The sea level variations along the south coast of Japan indicate that, prior to the generation of the large meander, the small meander in the Kuroshio was generated southeast of Kyushu and propagated eastward and that, just when this meander reached off Cape Shionomisaki, a large scale oceanic event covering over the whole region of the south coast of Japan occurred. This large scale event seems to be one of the necessary conditions for the generation of the large meander in the Kuroshio off Enshû-nada.  相似文献