摘要:

This contribution investigates the morphodynamic equilibrium of funnel‐shaped well‐mixed estuaries and/or tidal channels. The one‐dimensional de Saint Venant and Exner equations are solved numerically for the ideal case of a frictionally dominated estuary consisting of noncohesive sediment and with insignificant intertidal storage of water in tidal flats and salt marshes. This class of estuaries turns out to be invariably flood dominated. The resulting asymmetries in surface elevations and tidal currents lead to a net sediment flux within a tidal cycle which is directed landward. As a consequence, sediments are trapped within the estuary and the bottom profile evolves asymptotically toward an equilibrium configuration, allowing a vanishing net sediment flux everywhere and, in accordance with field observations, a nearly constant value of the maximum flood/ebb speed. Such an equilibrium bed profile is characterized by a concavity increasing as the estuary convergence increases and by a uniquely determined value of the depth at the inlet section. The final length of the estuary is fixed by the longitudinal extension of the very shallow area which tends to form in the landward portion of the estuary. Note that sediment advection is neglected in the analysis, an assumption appropriate to the case of not too fine sed

ISSN:0148-0227    

DOI:10.1029/2000JC000468

年代:2002

数据来源: WILEY

摘要:

In situ and satellite sea level data sets over 1980–1998 are used to estimate interannual variations of the geostrophic zonal transport from the western Pacific Ocean into the Celebes Sea. Then the transport component due to the Pacific wind‐driven and fully reflected equatorial waves is removed. Finally, the residual variations, named Indonesian throughflow correction (ITFC), are used to correct for the model closed western boundary. ITFC inflows/outflows are leading the warm/cold events by a few months. They are then prescribed at the model western boundary over 1980–1998 to compare with closed boundary simulations. An ITFC inflow anomaly makes the eastern Pacific slightly warmer and trade winds in the central Pacific slightly weaker. Indeed, these quantities are simulated by both experiments in very good agreement with observations. More importantly, prescribing the ITFC greatly improves two characteristics of the model that play a key role in the coupled simulations. The first is the RMS variability of sea level versus longitude; the ITFC shifts to the west the position of the minimum. The second is the basin average sea level; the ITFC largely amplifies its fluctuations, stimulating the charge and discharge of the system. Consequently, the ITFC can have a very large impact on El Niño‐Southern Oscillation forecasts. For example, the 1982/1983 and 1997/1998 1‐year lead forecasts which fail to predict the warm events with closed boundaries are successful with the ITFC. The impact of the ITFC on coupled simulations is not linearly dependent on the ITFC value itself: In addition to the fluctuating conditions at the western boundary, results depend on how close to instability the system is at each

ISSN:0148-0227    

DOI:10.1029/2000JC000615

年代:2002

数据来源: WILEY

摘要:

Two practical techniques of “correction method” and “fitting method” for computing major diurnal and semidiurnal tidal currents from irregular satellite‐tracked drifter position data have been developed and then applied to the Yellow and East China Seas to compute M2and K1currents. The correction method calculates the most dominant diurnal and semidiurnal tidal currents using the correction coefficients, defined amplitude ratios, and phase differences between the major tidal currents. On the other hand, the fitting method calculates major tidal currents by fitting the amplitudes and phases to a given polynomial function in space, without utilization of the correction coefficients. Validation tests for sampling intervals, data truncation, effects of low‐frequency currents, and position errors are performed to improve computation results. Both methods enable us to evaluate effectively and correctly strong tidal currents provided that the signal‐to‐noise level in drifter positions is not significantly high. The spatial pattern and current ellipses of M2and K1tidal currents from drifter positions in the Yellow Sea are fairly well consistent with those from moored current data. Application of the two methods to the Yellow and East China Seas exhibits commonly that M2and K1currents rotate clockwise in the East China Sea but counterclockwise in the Yellow Sea interior, with rotation direction change around 35° and 34

ISSN:0148-0227    

DOI:10.1029/2001JC000898

年代:2002

数据来源: WILEY

摘要:

A fully three‐dimensional model for the motion and bending of a solitary ice floe due to wave forcing is presented. This allows the scattering and wave‐ induced force for a realistic ice floe to be calculated. These are required to model wave scattering and wave‐induced ice drift in the marginal ice zone. The ice floe is modeled as a thin plate, and its motion is expanded in the thin plate modes of vibration. The modes are substituted into the integral equation for the water. This gives a linear system of equations for the coefficients used to expand the ice floe motion. Solutions are presented for the ice floe displacement, the scattered energy, and the time‐averaged force for a range of ice floe geometries and wave periods. It is found that ice floe stiffness is the most important factor in determining ice floe motion, scattering, and force. However, above a critical value of stiffness the floe geometry also influences the scattering an

ISSN:0148-0227    

DOI:10.1029/2000JC000713

年代:2002

数据来源: WILEY

摘要:

The wind‐ and buoyancy‐forced upper ocean circulation in a marginal sea connected to the open ocean through two straits is investigated using idealized numerical and analytical models. The study is motivated by the Japan/East Sea (JES) and other marginal seas found along the western North Pacific. It is shown that for anticyclonic wind stress curl and atmospheric cooling in the marginal sea, the inflow transport branches into eastern and western boundary currents, in qualitative agreement with observed branching of the Tsushima Current in the southern JES. The eastern boundary current arises because wind forcing in the open ocean, and a circulation integral around the island that separates the marginal sea from the open ocean, maintains the temperature on the island to be warmer than that found in the interior of the marginal sea. Buoyancy forcing in the marginal sea plays a key role in maintaining the eastern boundary current. The dynamics that control the water mass transformation and downwelling are described and related to the model parameters. The largest heat loss to the atmosphere is found in the eastern boundary current. The exchange rates with the open ocean, downwelling within the marginal sea, and current structure within the marginal sea predicted by a linear analytic theory compare closely with results from a shallow water numerical mo

ISSN:0148-0227    

DOI:10.1029/2001JC000966

年代:2002

数据来源: WILEY

摘要:

Three deep anticyclonic eddies of a species only reported once before [Gordon and Greengrove, 1986] were intersected by hydrographic lines of the World Ocean Circulation Experiment (WOCE) and South Atlantic Ventilation Experiment (SAVE) programs in the Argentine Basin. The vortices are centered near 3500 m depth at the interface between North Atlantic Deep Water and Bottom Water. They have ∼1500‐m‐thick cores containing Lower Circumpolar Deep Water and a dynamic influence that may span up to two thirds of the water column. As one eddy was observed just downstream of the western termination of the Falkland Escarpment, a destabilization of the deep boundary current by the sudden slope relaxation is suggested as a potential cause of eddy formation. Besides isopycnal interleaving at the eddy perimeters, strongly eroded core properties in the upper parts of the lenses, associated with low density ratios, hint at double diffusion at the top of the structures as another major decay mechanism. The presence of an eddy in the northern Argentine Basin shows the possibility for a northward drift of the vortices, in this basin at least. Deep events in recent current measurements from the Vema Channel are presented that raise the question of further equatorward motion to the Brazil

ISSN:0148-0227    

DOI:10.1029/2001JC000963

年代:2002

数据来源: WILEY

摘要:

We use a two‐dimensional, time‐dependent sediment‐transport model to quantify across‐shelf transport, deposition, and sorting during wave‐driven resuspension events characteristic of those that dominate sediment transport on many continental shelves. Decreases in wave‐orbital velocities as water depth increases, and the resulting cross‐shelf gradient in bed shear stress favor a net offshore transport of sediment. On wide, flat shelves (slopes ∼0.1%percnt;), these gradients are low, and the depth to which the seabed is reworked depends mainly on bottom shear stress and local sediment availability. On narrow, steep shelves (slopes ∼0.5%percnt;), however, the gradient in bottom stress generates significant cross‐shelf suspended sediment flux gradients that create regions of net erosion and deposition. While the magnitude of waves generally determines the water depth to which sediment can be resuspended, erosional and depositional patterns on narrow shelves are sensitive to cross‐shelf gradients in wave energy, nonlocal sediment availability, and the direction and magnitude of the cross‐shelf current. During energetic waves, cross‐shelf divergence of suspended sediment flux can create a coarsened, erosional area on the inner shelf that abuts a region of fine‐grained sediment deposition on the mid‐to‐outer shelf. If currents are strongly shoreward, however, flux divergence leads t

ISSN:0148-0227    

DOI:10.1029/2000JC000634

年代:2002

数据来源: WILEY