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81.
Naoto Ebuchi Yasushi Fukamachi Kay I. Ohshima Kunio Shirasawa Masao Ishikawa Toru Takatsuka Takaharu Daibo Masaaki Wakatsuchi 《Journal of Oceanography》2006,62(1):47-61
Three High Frequency (HF) ocean radar stations were installed around the Soya/La Perouse Strait in the Sea of Okhotsk in order
to monitor the Soya Warm Current (SWC). The frequency of the HF radar is 13.9 MHz, and the range and azimuth resolutions are
3 km and 5 deg., respectively. The radar covers a range of approximately 70 km from the coast. The surface current velocity
observed by the HF radars was compared with data from drifting buoys and shipboard Acoustic Doppler Current Profilers (ADCPs).
The current velocity derived from the HF radars shows good agreement with that observed using the drifting buoys. The root-mean-square
(rms) differences were found to be less than 20 cm s−1 for the zonal and meridional components in the buoy comparison. The observed current velocity was also found to exhibit reasonable
agreement with the shipboard ADCP data. It was shown that the HF radars clearly capture seasonal and short-term variations
of the SWC. The velocity of the Soya Warm Current reaches its maximum, approximately 1 m s−1, in summer and weakens in winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately
40 km. The surface transport by the SWC shows a significant correlation with the sea level difference along the strait, as
derived from coastal tide gauge records at Wakkanai and Abashiri.
Deceased. 相似文献
82.
Sensitivity analysis of a coastal marine ecosystem 总被引:1,自引:0,他引:1
An ecosystem with four compartments, i.e. PO4-P, phytoplankton, zooplankton and detritus, in a coastal region was considered. Sensitivity analysis of a phosphorus flow model in well-mixed water without currents concludes that (1) the maximal photosynthetic rate,V
m
, in Michaelis-Menten relation plays an important role in the distribution of biomass among compartments but the half saturation constant,K
s
, is not so important, (2) the natural death rate of phytoplankton is important for the ecosystem, (3) the natural death rate of zooplankton is also effective on the ecosystem.A numerical experiment was also performed on the ecosystem with four compartments are also studied using a dynamical barotropic model of tidal currents of Mikawa Bay (Japan). Diffusion coefficient in diffusion equation plays the role of a linear smoothing parameter in the horizontal distribution of compartment. On the other hand, perturbations of biological parameters cause nonlinear variations in the horizontal distribution of compartment. 相似文献
83.
Field observation was conducted to monitor phosphate concentrations in groundwater and seawater mixing at two sandy beaches in Futtsu and Miura in Tokyo Bay, Japan. Dissolved phosphate concentrations were measured along transects from fresh groundwater aquifer to seawater adjacent the beaches. The concentrations were often high (up to 46 µM) in fresh groundwater samples (Cl– < 0.2). Coastal seawater, on the other hand, exhibited low phosphate concentrations (1.5 µM or less). Along the transects, phosphate generally displayed non-conservative behavior during mixing of fresh and saline waters in the aquifer; concentrations as high as 100 µM were found around the upper limit of seawater intrusion (Cl– = 2). Laboratory experiments were executed to identify the processes that control the phosphate behavior in the mixing processes. The results revealed that adsorption-desorption processes by the aquifer sand particles could significantly control the phosphate concentrations in the groundwater. Furthermore, the adsorption and/or desorption was found to be a function of salinity; the equilibrium concentration of dissolved phosphate in slurry of sand and water was the highest in freshwater and decreased considerably in saline water. The extreme concentration of phosphate may be caused by release from sand particles coinciding with the rapid change in salinity with tide. 相似文献
84.
Tomohiro Nakamura Takahiro Toyoda Yoichi Ishikawa Toshiyuki Awaji 《Journal of Oceanography》2004,60(2):411-423
A numerical study using a 3-D nonhydrostatic model has been applied to baroclinic processes generated by the K
1 tidal flow in and around the Kuril Straits. The result shows that large-amplitude unsteady lee waves are generated and cause
intense diapycnal mixing all along the Kuril Island Chain to levels of a maximum diapycnal diffusivity exceeding 103 cm2s−1. Significant water transformation by the vigorous mixing in shallow regions produces the distinct density and potential vorticity
(PV) fronts along the Island Chain. The pinched-off eddies that arise and move away from the fronts have the ability to transport
a large amount of mixed water (∼14 Sv) to the offshore regions, roughly half being directed to the North Pacific. These features
are consistent with recent satellite imagery and in-situ observations, suggesting that diapycnal mixing within the vicinity
of the Kuril Islands has a greater impact than was previously supposed on the Okhotsk Sea and the North Pacific. To examine
this influence of tidal processes at the Kurils on circulations in the neighboring two basins, another numerical experiment
was conducted using an ocean general circulation model with inclusion of tidal mixing along the islands, which gives a better
representation of the Okhotsk Sea Mode Water than in the case without the tidal mixing. This is mainly attributed to the added
effect of a significant upward salt flux into the surface layer due to tidal mixing in the Kuril Straits, which is subsequently
transported to the interior region of the Okhotsk Sea. With a saline flux into the surface layer, cooling in winter in the
northern part of the Okhotsk Sea can produce heavier water and thus enhance subduction, which is capable of reproducing a
realistic Okhotsk Sea Mode Water. The associated low PV flux from the Kuril Straits to the open North Pacific excites the
2nd baroclinic-mode Kelvin and Rossby waves in addition to the 1st mode. Interestingly, the meridional overturning in the
North Pacific is strengthened as a result of the dynamical adjustment caused by these waves, leading to a more realistic reproduction
of the North Pacific Intermediate Water (NPIW) than in the case without tidal mixing. Accordingly, the joint effect of tidally-induced
transport and transformation dominating in the Kuril Straits and subsequent eddy-transport is considered to play an important
role in the ventilation of both the Okhotsk Sea and the North Pacific Ocean.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
85.
Masahiro Endoh 《Journal of Oceanography》1977,33(1):6-15
A numerical study of characteristics of the front formed by cooling of the sea surface and inflow of the fresh water is made within a vertical two-dimensional plane without the rotation of the earth. The convective adjustment technique is employed to parameterize the small scale convective overturning process.A sharply edged shelf causing the marked difference of the heat capacity of the water columns between over the shelf (50 m depth) and in the deeper region (150 m depth), is responsible for the formation of a thermal front over the shelf edge and two cell circulations of the same sense with each other adjoining at the frontal region.Inflow of the fresh water at the upper region of the coast (which is equivalently replaced by the outflow of the salt from the same region) adds a circulation of the opposite sense to the above ones, which transports the water of low salinity and low temperature offshore and forms a sharp front both of temperature and salinity with the offshore water of high salinity and high temperature. This thermohaline front or Oceanic front has a remarkable character that the horizontal density gradient is minimal at the front due to the counteracting contributions of temperature and salinity to density. Response of this front to the sudden ceases of the surface cooling and the fresh water supply, is also studied in order to understand its transient behaviors. 相似文献
86.
Masahiro Endoh 《Journal of Oceanography》1973,29(4):148-154
Dynamics of western boundary currents in the subtropical and subpolar gyres are studied as a source-sink flow of barotropic fluid by means of numerical integration of the time-dependent non-linear vorticity equation. The bottom topography consists of a continental shelf of uniform slope (120 km wide) parallel to the straight western coast and a flat bottom of uniform depth. The steady solution in the case of low Reynolds number (Re≦100) shows the vorticity balance of the western boundary current between theβ-, diffusion-, and bottom relief terms. The cuspidated flow of the western boundary current in the subpolar gyre is observed as a compensating flow for the subtropical western boundary current separating from the western coast. In the case of Re=350, the zonal current separating from the coast meanders with the wave length of the stationary Rossby waves. It is shown that in the present model the separation of the boundary current is controlled by the planetary vorticity (f) of the fluid particle in the boundary flow, with which the same particle flows out the eastern wall at the corresponding latitude. The decrease of the efflux width increases the intensity of the non-linear overshooting of the boundary current separating from the western coast. 相似文献
87.
Masahiro Endoh 《Journal of Oceanography》1980,36(2):134-140
Summarized is the author's study of the ocean circulation dynamics with numerical models, for which he was honored by the
Okada Prize (1979). Cited topics are formation of the western boundary current and its variation associated with imposed wind
stress, some effects of a marine ridge on the boundary current, coastal upwelling circulation and coastal thermohaline front
formation. Recent modelling efforts in Japan, specifically on numerical study of ocean circulation dynamics are also reviewed. 相似文献
88.
To understand the behavior of manganese in diagenetic processes in sediments of an enclosed bay which is similar to those
of an estuary, chemical analyses have been carried out on both sediment and interstitial water of a core sample collected
from Tokyo Bay. The results suggest that redistribution of manganese takes place within the sediment as a result of the dissolution
of buried manganese oxides and hydroxides under reducing condition, the downward diffusion of Mn2+ through the interstitial water toward lower layers and then the precipitation of carbonate. The carbonate formed in the sediment
contains managanese carbonate probably as a solid solution between calcitic calcium carbonate and manganese carbonate. 相似文献
89.
In order to examine the formation, distribution and transport of North Pacific Intermediate Water (NPIW), repeated hydrographic
observations along several lines in the western North Pacific were carried out in the period from 1996 to 2001. NPIW formation
can be described as follows: (1) Oyashio water extends south of the Subarctic Boundary and meets Kuroshio water in intermediate
layers; (2) active mixing between Oyashio and Kuroshio waters occurs in intermediate layers; (3) the mixing of Oyashio and
Kuroshio waters and salinity minimum formation around the potential density of 26.8σθ proceed to the east. It is found that Kuroshio water flows eastward even in the region north of 40°N across the 165°E line,
showing that Kuroshio water extends north of the Subarctic Boundary. Volume transports of Oyashio and Kuroshio components
(relative to 2000 dbar) integrated in the potential density range of 26.6–27.4σθ along the Kuroshio Extension across 152°E–165°E
are estimated to be 7–8 Sv (106 m3s−1) and 9–10 Sv, respectively, which is consistent with recent work.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
90.
The Japanese government is committed to resuming sustainable commercial whaling, both on the high seas and along the Japanese coastline. To this end scientific whaling programs are supported with public money and the byproducts of the catch are distributed to the public and utilized in a variety of ways. Here we review the policies which govern how these byproducts are disseminated within Japan, as well as how the population as a whole makes use of whale resources. Possibilities for the future, if and when the international moratorium on commercial whaling ends, are also discussed. 相似文献