Branching of the Tsushima Current by an Abrupt Increase of Bottom Depth     

Young Ho Seung 《Journal of Oceanography》2005,61(2):261-269

An analytical model of the branching of an inertial current partly afloat incident upon a step fall in bottom topography is considered to account for the branching of the Tsushima Current induced by an abrupt increase of the bottom depth near the northern end of the Korea-Tsushima Strait. The grounded portion of the incident current is constraint by bottom topography and eventually runs along the depth discontinuity over the shallow region. Due to the inertia of the incident current, however, the ungrounded portion crosses the depth discontinuity and forms a free inertial jet, giving rise to the branching. The deflection angle of this free inertial jet is determined through an integrated momentum balance. The branching is more restricted as the grounded portion of the incident current becomes relatively more important, in terms of the momentum transport, than the ungrounded portion. For typical values of the bottom depth, the transport of the Tsushima Current through the Korea-Tsushima Strait, and for acceptable values of other physical parameters, it appears that branching is possible. Hence, the abrupt increase of the bottom depth near the northern end of the Korea-Tsushima Strait, combined with the inertia of current, may indeed be an important factor in the branching of the Tsushima Current.  相似文献   

A second-order particle tracking method     

Seok Lee  Heung-Jae Lie  Kyu-Min Song  Chong-Jeanne Lim 《Ocean Science Journal》2005,40(4):201-208

An accurate particle tracking method for a finite difference method model is developed using a constant acceleration method. Being assumed constant temporal and spatial gradients, the new method permits temporal-spatial variability of particle velocity. Test results in a solid rotating flow show that the new method has second-order accuracy. The performance of the new method is compared with that of other methods; the first-order Euler forward method, and the second-order Euler predictorcorrector method. The new method is the most efficient method among the three. It is more accurate and efficient than the other two.  相似文献   

Significance of Shallow Bottom Friction in the Dynamics of the Tsushima Current   总被引：1，自引：0，他引：1  

Young Ho Seung 《Journal of Oceanography》2003,59(1):113-118

A simple analytical model is considered for the dynamics of volume transport of the Tsushima Current. This model is basically baroclinic but allows bottom friction over the shallow regions connecting the Pacific Ocean to the Japan Sea basin, and is thus different from previous models which are either purely barotropic with bottom friction predominating over the whole domain, or purely baroclinic with bottom friction completely ignored. Compared to the previous barotropic model, this model is not only more realistic but also gives much simpler results. It gives the observed downstream sea level slope, which is not seen in the previous baroclinic model. As a result, the estimated transport of the Tsushima Current is closer to the observational data than those of previous models. This model indicates that the localized bottom friction acting over the shallow regions not only controls the transport of the Tsushima Current but also moves the stagnation point of the western boundary current northward. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Magnitude and variability of Holocene sediment accumulation in Santa Monica Bay,California     

Sommerfield CK  Lee HJ 《Marine environmental research》2003,56(1-2):151-176

The spatial variability of Holocene (past 10,000 years) sediment accumulation in Santa Monica Bay (California) was examined to identify controls sediment trapping in a bathymetrically complex coastal embayment and to provide geologic context for the post-industrial sedimentary record and associated pollution gradients. Sediment chronologies based on downcore AMS 14C dates were used to quantify long-term (millennia) accumulation rates in an effort to elucidate particle-transport pathways and sinks. Sediment accumulation rates for the full range of bayfloor environments (50-630 m water depths) range from 22 to 102 mg/cm(2)/year (15-88 mm/100 year), have an overall mean of 51+/-21 mg/cm(2)/year (1 sigma, n=11), and are comparable to rates reported for adjacent borderland basins. Maximal accumulation rates on the Malibu shelf and within a reentrant to Redondo canyon are interpreted to reflect (1) proximity to sediment sources and (2) localized oceanographic and topographic conditions conducive to sediment trapping and deposition. The 14C-derived accumulation rates are 2-10 times lower than rates determined through (210)Pb geochronology for the same sites in a related study, revealing that Holocene sediment accumulation has been non-steady-state. Santa Monica Bay is an important sink for suspended matter; averaged over the past several millennia a mass of sediment equivalent to 10-80% of the modern annual river supply is sequestered yearly. Net influx of suspended matter derived from the adjacent Palos Verdes shelf is evinced by a concentration gradient of p,p'-DDE in bayfloor sediments, whereas the distribution of anthropogenic silver suggests transport from Santa Monica shelf to the southeastern boundary of the bay. The results of this study provide new insight to the long-term fates of particulate matter in Los Angeles coastal waters.  相似文献   

Water surface resonance in the L-shaped channel of seawater exchange breakwater     

Changhoon Lee  Dal Soo Lee 《Ocean Engineering》2003,30(18):2423-2436

The resonance period of the L-shaped channel in the caisson is predicted analytically for the seawater exchange breakwater of “Applicability Study of the Seawater Exchange Breakwater (1). Korea Ministry of Maritime Affairs and Fisheries (in Korean) (1999a)”. Hydraulic experiments are conducted for a composite breakwater with a rear reservoir that is one of the seawater exchange breakwaters developed by them. For regular waves, the water surface elevation in the channel and the flow rate through the breakwater are measured. For irregular waves, the flow rate through the breakwater and the reflection coefficient on the breakwater are measured. The resonant maximum values in both the surface elevation and the flow rate, and the resonant minimum values in the reflection coefficient are all at wave periods slightly longer than analytically predicted ones. The measured resonance period for irregular waves is closer to the predicted one than for regular waves. If the resonance period of the L-shaped channel is fitted to the dominant period of incident waves, there would be high efficiency of seawater exchange between inside and outside the harbor.  相似文献   

Indicators for ecosystem-based management on the Scotian Shelf: bridging the gap between theory and practice     

O'Boyle  R.; Sinclair  M.; Keizer  P.; Lee  K.; Ricard  D.; Yeats  P. 《ICES Journal of Marine Science》2005,62(3):598-605

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Data Assimilation Modeling of the Barotropic Tides in the Korea/Tsushima Strait     

Jeffrey?W.?BookEmail author  Pavel?Pistek  Henry?Perkins  Keith?R.?Thompson  William?J.?Teague  Gregg?A.?Jacobs  Moon-Sik?Suk  Kyung-Il?Chang  Jae-Chul?Lee  Byung?Ho?Choi 《Journal of Oceanography》2004,60(6):977-993

During 1999–2000, 13 bottom mounted acoustic Doppler current profilers (ADCPs) and 12 wave/tide gauges were deployed along two lines across the Korea/Tsushima Strait, providing long-term measurements of currents and bottom pressure. Tidally analyzed velocity and pressure data from the moorings are used in conjunction with other moored ADCPs, coastal tide gauge measurements, and altimeter measurements in a linear barotropic data assimilation model. The model fits the vertically averaged data to the linear shallow water equations in a least-squares sense by only adjusting the incoming gravity waves along the boundaries. Model predictions are made for the O₁, P₁, K₁, μ₂, N₂, M₂, S₂, and K₂ tides. An extensive analysis of the accuracy of the M₂ surface-height predictions suggests that for broad regions near the mooring lines and in the Jeju Strait the amplitude prediction errors are less than 0.5 cm. Elsewhere, the analysis suggests that errors range from 1 to 4 cm with the exception of small regions where the tides are not well determined by the dataset. The errors in the model predictions are primarily caused by bias error in the model’s physics, numerics, and/or parameterization as opposed to random errors in the observational data. In the model predictions, the highest ranges in sea level height occur for tidal constituents M₂, S₂, K₁, O₁, and N₂, with the highest magnitudes of tidal velocities occurring for M₂, K₁, S₂, and O₁. The tides exhibit a complex structure in which diurnal constituents have higher currents relative to their sea level height ranges than semi-diurnal constituents.  相似文献   

Biomarker responses in Macoma nasuta (Bivalvia) exposed to sediments from northern San Francisco Bay     

Ingeborg Werner  Swee J. Teh  Seema Datta  XiaoQiao Lu  Thomas M. Young 《Marine environmental research》2004,58(2-5):299

Our study investigates biomarker responses and survival of Macoma nasuta exposed to sediments collected from six locations in northern San Francisco Bay. Biomarkers analyzed were stress proteins (hsp70) in gill, mantle and digestive gland, lysosomal membrane damage and histopathologic lesions. Sediments and clam tissues were analyzed for a comprehensive suite of heavy metals and trace organic pollutants. Sediment grain size and organic carbon content were determined. Clams accumulated metals, polyaromatic hydrocarbons (PAHs) and organochlorine pesticides (aldrin and p,p^′-DDT and its metabolites p,p^′-DDD and p,p^′-DDE). Pearson and Spearman correlation analysis revealed that mortality, hsp70 in gill and histopathologic lesion scores in gonads, and lysosomal membrane damage were significantly correlated with tissue concentrations of DDT and/or its metabolites. Tissue concentrations of metals, in particular nickel, chromium, and copper, were associated with macrophage aggregates in digestive gland and germ cell necrosis. Cadmium was linked to mortality and lysosomal membrane damage.  相似文献   

Influence of mesoscale oceanographic processes on larval distribution and stock structure in jackass morwong (Nemadactylus Macropterus: Cheilodactylidae)     

Bruce  B. D.; Evans  K.; Sutton  C. A.; Young  J. W.; Furlani  D. M. 《ICES Journal of Marine Science》2001,58(5):1072-1080

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Variations in the abundance of fisheries resources and ecosystem structure in the Japan/East Sea   总被引：1，自引：0，他引：1  

Chang Ik Zhang  Jae Bong Lee  Young Il Seo  Sang Cheol Yoon  Suam Kim 《Progress in Oceanography》2004,61(2-4):245

Evidence supports the hypothesis that two climatic regime shifts in the North Pacific and the Japan/East Sea, have affected the dynamics of the marine ecosystem and fisheries resources from 1960 to 2000. Changes in both mixed layer depth (MLD) and primary production were detected in the Japan/East Sea after 1976. The 1976 regime shift appears to have caused the biomass replacement with changes in catch production of major exploited fisheries resources, including Pacific saury, Pacific sardine and filefish. Both fisheries yield and fish distribution are reflected in these decadal fluctuations. In the 1960s and 1990s, common squid dominated the catches whereas in the 1970s and 1980s, it was replaced by walleye pollock. In the post-1988 regime shift, the distribution of horse mackerel shifted westward and southward and its distributional overlap with common mackerel decreased. The habitat of Pacific sardine also shifted away from mackerel habitats during this period. To evaluate changes in the organization and structure of the ecosystem in the Japan/East Sea, a mass-balanced model, Ecopath, was employed. Based on two mass-balanced models, representing before (1970–75) and after (1978–84) the 1976 regime shift, the weighted mean trophic level of catch increased from 3.09 before to 3.28 after. Total biomass of species groups in the Japan/East Sea ecosystem increased by 15% and total catch production increased by 48% due to the 1976 regime shift. The largest changes occurred at mid-trophic levels, occupied by fishes and cephalopods. The dominant predatory species shifted from cephalopods to walleye pollock due to the 1976 regime shift. It is concluded that the climatic regime shifts caused changes in the structure of the ecosystem and the roles of major species, as well as, large variations in biomass and production of fisheries resources.  相似文献