Influence Of Bottom Topography Research Articles

The Influence of Bottom Topography on Baroclinic Transports

Abstract A new and reduced set of governing equations is proposed for the modeling of baroclinic motions in a two-layer system with variable bottom topography. The reduction of the equations, which eliminates all barotropic is based on the assumption of almost vertically compensated transports. The resulting equations differ somewhat from those obtained with a rigid-lid approximation. The limitations are topography variability only on horizontal scales greater than the wavelength and wavelengths shorter than the barotropic radius of deformation. These are not critical in many problems. Numerical solutions to the reduced equations are shown to be close to those obtained from the primitive equations, in one- and two-dimensional cases. In view of their relative simplicity, the new governing equations have also been applied to the analytical study of coastal upwelling in the presence of variable topography. It is shown then that the presence of a canyon enhances coastal upwelling. The success of the reduced e...

The Influence of Bottom Topography on Upwelling off Peru

Abstract The x-y-t, two-layer β-plane numerical model developed by Hurlburt (1974) is used to examine the upwelling system off Peru. The region off Peru from 14 to 15°30's is one of strong and persistent upwelling. The most distinctive feature of the Peruvian upwelling circulation is a predominant poleward flow. A local area model, when forced by wind stress only, cannot account for the observed Peruvian circulation. When an additional barotropic forcing is applied in the model, a dominating poleward flow results. The effects of wind stress are felt on the upper layer and by the third day of integration an equatorward flow develops near the coast. Two functional representations of the actual topography are used in the model and compared to a flat-bottom case. Model results, when compared to observations, show that the observed upwelling maximum ∼40 km south of 15°S is the result of a mesoscale topographic feature, a seamount. Variations of longshore and cross-shelf flow in cases with sloping topography ar...

Design and preliminary testing of a continuous offshore resistivity method

A continuous offshore resistivity method has been designed for use in shallow, multimethod, marine geophysical surveys. This inexpensive system employs towed electrodes near the sea surface and is compatible with other ship-board equipment. Limited field testing indicates that the offshore resistivity results obtained, after processing to assess the influence of bottom topography, contain useful information on lateral sub-bottom resistivity contrasts which may be of geological significance. Further testing and development of the method appears to be warranted as it should not only provide additional data on sub-bottom material but could be extremely useful in studying the conductive overburden problem often encountered in galvanic surveys on land.

Planetary-type Waves in the South West Indian Ocean

SOUTH of the latitude of the Cape of Good Hope, the Agulhas Current Stream (or at least most of it) turns back into the Indian Ocean and forms a zonal current called the Agulhas Return Current, whose mean axis of flow is approximately 38°–39°S. Near the start of its eastward flow, the Agulhas Return Current has been shown to undergo sharp changes of direction (Fig. 1a). These deflections are apparent in the analysis made by Dietrich1 and Le Pichon2. The latter shows them occurring down to the depth of the salinity maximum and draws attention to the important influence of bottom topography. They are also very evident in the study made by Darbyshire3 of data from the cruises of SAS Natal and RS Africana II, occurring in three out of the four seasons examined. The deflections all occur near a prominent topographical feature, the Agulhas Plateau, and their recurrence suggests that they are a quasi-stationary feature and possibly planetary waves caused by the rapid changes in water depth. An investigation into this possibility has been made by comparing the flow patterns deduced from hydrological data with those predicted by theory.

Topographic effects on the wind‐driven ocean circulation

Abstract This is a study of the influence of bottom topography of an ocean basin on the wind‐driven, barotropic ocean circulation. A detailed investigation is made of the role of vorticity transfer to the ocean bottom in the presence of varying topography. It is shown that the wind‐driven gyre over the topography of the North Atlantic has a transport in the western part of the basin only half of that obtained in an ocean of constant depth.

The Influence of Bottom Topography on the Stability of Jets in a Baroclinic Fluid

Abstract The stability of a two-layer model is analyzed using a numerical method taking into account the effect of bottom topography. A jet in geostropic equilibrium exists in the upper layer and baroclinic instability may occur. It is found if the bottom topography has a large amplitude relative to the total depth, that it has a destabilizing rather than a stabilizing influence. Applying the model to the Gulf Stream, it is found that the most unstable disturbances, corresponding to the basic flow upstream from Cape Hatteras, are markedly different in wavelength and period from those corresponding to the basic flow downstream from Hatteras. The baroclinic disturbances in the model are consistent with the limited observational evidence on momentum transfer by Gulf Stream eddies.

On the wind-driven circulation in an ocean with bottom topography

The influence of bottom topography on the wind-driven ocean circulation is investi gated for a homogeneous, s-plane model with an imposed, steady wind stress curl. The linear model studied by Munk (1950) and the non-linear model studied by Carrier & Robinson (1962) are special cases as is the simple model proposed by Warren (1963) foi the description of Gulf Stream meanders. Although the effects of density stratification are neglected, inertial and frictional effects are included and solutions determined for various kinds of topography. Simple analytic models are examined and found to be useful in describing limited regions of the ocean basin. In particular the concept of an interior regime, in which nonlinear and frictional terms are unimportant, can be extended to the case of variable depth. In regions of strong inertial flow over topography, the simple meander model investigated by Rossby (1940) has some success in predicting the path of the stream. In both models the importance of isopleths of constant F/H , where F is the Coriolis parameter and H is the depth, is demonstrated by showing that there is a strong tendency for streamlines to follow or meander about such curves. Complete numerical solutions are found for the finite difference vorticity equation by an efficient relaxation scheme developed for this purpose. Results show that the response of the ocean may be strongly controlled by the shape of the ocean bottom and that such gross features of the ocean circulation as Gulf Stream separation, meandering, and variable transport may be related to topograpic effects. DOI: 10.1111/j.2153-3490.1967.tb01510.x

On the Influence of Bottom Topography on Ocean Currents

On the Influence of Bottom Topography on Ocean Currents