On the Utility and Disutility of JEBAR

The usefulness of the concept of JEBAR, the joint effect of baroclinicity and relief, in large-scale ocean dynamics is critically analyzed. The authors address two questions. Does the JEBAR term properly characterize the joint impact of stratification and bottom topography on the ocean circulation? Do estimates of the JEBAR term from observational data allow reliable diagnostic calculations? The authors give a negative answer to the first question. The JEBAR term need not give a true measure of the effect of bottom relief in a stratified ocean. A simple two-layer model provides examples. As to the second question, it is demonstrated that the large-scale pattern of the transport streamfunction is captured by the smoothed solution, especially with the Mellor et al. formulation of the JEBAR term. However, the calculated velocity field is very noisy and the relative errors are large

The Influence of the Pressure Head on the Indonesian Seas Circulation

A high resolution, regional, non-linear, barotropic ocean model (2D POM) was used to show that a pressure difference between the Pacific and Indian Ocean does not significantly influence the total transport of the Indonesian throughflow

Dynamical Balance in the Indonesian Seas Circulation

A high resolution, four-open port, non-linear, barotropic ocean model (2D POM) is used to analyze the Indonesian Seas circulation. Both local and overall momentum balances are studied. It is shown that geostrophy holds over most of the area and that the Pacific-Indian Ocean pressure difference is essentially balanced by the resultant of pressure forces acting on the bottom

On the evolution of Rossby waves, generated by wind stress in a closed basin, incorporating total mass conservation

The evolution of Rossby waves generated in a closed basin by applied stationary wind stress is considered, taking into account the total mass conservation constraint. The behavior of the wave field for large time t and the formation of a Sverdrup regime in the open ocean are analyzed by neglecting the frictionally induced wave decay. The consistent quasigeostrophic formulation of the problem is developed and the conditions are found for the applicability of relations derived. Using the vertical mode expansion reduces the 3D problem to a set of 2D problems. A method of solving the forced 2D problem with the mass constraint is suggested. The method consists of solving several particular problems, the most important of which are the forced problem for the auxiliary stream function Ψ τ with zero boundary values and the Volterra integral equation of the second kind for time-dependent boundary values of the stream function Ψ. To simplify the analysis, the 1D model of the forced problem considered is offered. The analytical solution of the problem with zero boundary values of the stream function Ψ is found. It is known that, in general, such a solution does not stabilize with time but for large values of m (the ratio of the basin dimension to the Rossby radius of deformation) and t it tends to the Sverdrup solution in the open ocean. The time-averaged stream function Ψ is introduced, which tends to the Sverdrup solution in the open ocean for all m. A solution of the consistent problem satisfying the total mass conservation constraint is obtained and analyzed. It is pointed out that the stream function Ψ does not tend to the Sverdrup solution outside the western boundary layer for large values of m and t, which differs drastically from the corresponding behavior of Ψ in the problem with zero boundary values. This demonstrates the failure of the solution of the inconsistent problem with zero boundary values to describe the wave motion for large t. It is shown that the establishment of the Sverdrup solution for large t can be seen only if the time-averaged stream function Ψ is considered. It is proved for all m that outside the western boundary layer Ψ tends to the Sverdrup solution (minus the integral of Ψ in x over the whole basin) for large t. The evolution of the total energy is also discussed

On the Divergence-Form Finite-Difference Approximation to the Momentum Advection in Curvilinear Orthogonal Coordinates

The traditional finite-difference schemes for the dynamical equations in curvilinear orthogonal coordinates have a basic flaw: they conserve only energy, but not momentum. A finite-difference approximation to these equations is suggested that conserves both energy and momentum. (C) 2000 Elsevier Science Ltd. All rights reserved

On the Transition Between Different Dynamical Regimes of the Antarctic Circumpolar Current

Two different dynamical regimes of the Antarctic Circumpolar Current are considered: the Sverdrup regime and the frictionally controlled one. In the former the intensity of the current does not depend on friction, while in the latter it is inversely proportional to the coefficient of friction. The transition between these two regimes is studied. It is shown that the frictionally controlled regime is generated not only in the case of closed isolines of ambient potential vorticity q. The regime is formed in the case of blocked (or partially blocked) q isolines as well, if the slope of the q isolines in the zonal direction is sufficiently small

Dynamics of the Indonesian seas circulation. Part I – The influence of bottom topography on temperature and salinity distributions

The influence of bottom topography on the distribution of temperature and salinity in the Indonesian seas region has been studied with a high-resolution model based on the Princeton Ocean Model. One of the distinctive properties of the model is an adequate reproduction of all major topographic features in the region by the model bottom relief. The three major routes of flow of Pacific water through the region have been identified. The western route follows the flow of North Pacific Water through the Sulawesi Sea, Makassar Strait, Flores Sea, and Banda Sea. This is the main branch of the Indonesian Throughflow. The eastern routes follow the flow of South Pacific water through the eastern Indonesian seas. This water enters the region either through the Halmahera Sea or by flowing to the north around Halmahera Island into the Morotai Basin and then into the Maluku Sea. A deep southward flow of South Pacific Water fills the Seram Sea below 1200 to through the Lifamatola Passage. As it enters the Seram Sea, this overflow turns eastward at depths greater than 2000 m, then upwells in the eastern part of the Seram Sea before returning westward at similar to 1500-2000 m. The flow continues westward across the Seram Sea, spreading to greater depths before entering the Banda Sea at the Buru-Mangole passage. It is this water that shapes the temperature and salinity of the deep Banda Sea. Topographic elevations break the Indonesian seas region down into separate basins. The difference in the distributions of potential temperature, theta, and salinity, S, in adjacent basins is primarily due to specific properties of advection of theta and S across a topographic rise. By and large, the topographic rise blocks deep flow between basins whereas water shallower than the depth of the rise is free to flow between basins. To understand this process, the structure of simulated fields of temperature and salinity has been analyzed. To identify a range of advected theta or S, special sections over the sills with isotherms or isohalines and isotachs of normal velocity have been considered. Following this approach the impact of various topographic rises on the distribution of theta and S has been identified. There are no substantial structural changes of potential temperature and salinity distributions between seasons, though values of some parameters of temperature and salinity distributions, e.g., magnitudes of maxima and minima, can change. It is shown that the main structure of the observed distributions of temperature and salinity is satisfactorily reproduced by the model throughout the entire domain

On the Time-Splitting Scheme Used in the Princeton Ocean Model

The analysis of the time-splitting procedure implemented in the Princeton Ocean Model (POM) is presented. The time-splitting procedure uses different time steps to describe the evolution of interacting fast and slow propagating modes. In the general case the exact separation of the fast and slow modes is not possible. The main idea of the analyzed procedure is to split the system of primitive equations into two systems of equations for interacting external and internal modes. By definition, the internal mode varies slowly and the crux of the problem is to determine the proper filter, which excludes the fast component of the external mode variables in the relevant equations. The objective of this paper is to examine properties of the POM time-splitting procedure applied to equations governing the simplest linear non-rotating two-layer model of constant depth. The simplicity of the model makes it possible to study these properties analytically. First, the time-split system of differential equations is examined for two types of the determination of the slow component based on an asymptotic approach or time-averaging. Second, the differential-difference scheme is developed and some criteria of its stability are discussed for centered, forward, or backward time-averaging of the external mode variables. Finally, the stability of the POM time-splitting schemes with centered and forward time-averaging is analyzed. The effect of the Asselin filter on solutions of the considered schemes is studied. It is assumed that questions arising in the analysis of the simplest model are inherent in the general model as well. (C) 2009 Elsevier Inc. All rights reserved