A three-dimensional model of the Southern Ocean with bottom topography

Johnson, John A.; Hill, Rebekah

doi:10.1016/0011-7471(75)90079-0

Cited by 16 publications

(19 citation statements)

References 4 publications

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“…In the following, a barotropic linear model will be used to examine the role of the local wind. It is possible to construct a solution for the currents in a homogeneous fluid in a region of closed f / H if the winds and bathymetry are known [ Kamenkovich , 1962; Johnson and Hill , 1975; Johnson , 1998; Dewar , 1998; Isachsen et al , 2003]. A difficulty arises with stratification since momentum must be transferred through fluid layers downward to the bottom Ekman layer to balance the surface forcing.…”

Section: Origin Of the Algerian Gyresmentioning

confidence: 99%

The mean circulation of the southwestern Mediterranean Sea: Algerian Gyres

et al. 2005

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This is a study about the general circulation of the southwestern Mediterranean Sea based on observations of currents carried out in the southwestern Mediterranean Sea in the framework of the Mass Transfer and Ecosystem Response (MATER) program (EEC/MAST3 program). From July 1997 to August 2002, profiling floats (MEDPROF experiment), isobaric floats (LIWEX experiment), and moored current meters (ELISA experiment) give evidence of two large-scale barotropic cyclonic circulations, the here-called Western and Eastern Algerian Gyres, centered around [3730'N, 230'E] and [3830'N, 600'E], respectively. These gyres have typical horizontal scales of 100-300 km and are characterized by orbital velocities of about 5 cm/s corresponding to rotational periods of about 4 months. They are strongly related to the bottom topography of the basin and to the planetary vorticity gradient: closed f/H isocontours (f is the planetary vorticity, H the water depth) correspond to the locations of the gyres and favor such circulations as free geostrophic modes. A linear and barotropic model is used to investigate the possibility of wind driving, but the results suggest that the wind stress is not responsible for establishing such circulations. The boundary currents flowing along the continental slope of Africa, Sardinia, and the Balearic Islands are proposed to be the main drivers of these gyres

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Section: Origin Of the Algerian Gyresmentioning

confidence: 99%

The mean circulation of the southwestern Mediterranean Sea: Algerian Gyres

et al. 2005

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“…But inclusion of a realistic or idealized bottom relief did not provide circulations with more realistic transports since these were generally far too weak (e.g. Johnson and Hill 1975, Klinck 1991, Krupitsky and Cane 1994, Wang and Huang 1995, Krupitsky et al 1996. Analytical models with baroclinicity are rare.…”

Section: Introductionmentioning

confidence: 99%

Six circumpolar currents—on the forcing of the Antarctic Circumpolar Current by wind and mixing

2006

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The transport of the Antarctic Circumpolar Current (ACC) is influenced by a variety of processes and parameters. A proper implementation of basin geometry, ocean topography and baroclinicity is known to be a fundamental requisite for a realistic simulation of the circulation and transport. Other, more subtle parameters are those of eddy-induced transports and diapycnal mixing of thermohaline tracers or buoyancy, either treated by eddy resolution or by a proper parameterization. Quite a number of realistic numerical simulations of the circulation in the Southern Ocean have recently been published. Many concepts on relations of the ACC transport to model parameters and forcing function are in the discussion, however, without much generality and little success.We present a series of numerical simulations of circumpolar flow with a simplified numerical model, ranging from flat-bottom wind-driven flow to baroclinic flow with realistic topography and wind and buoyancy forcing. Analysis of the balances of momentum, vorticity and baroclinic potential energy enables us to develop a new transport theory, which combines the most important mechanisms driving the circulation of the ACC and determining its zonal transport. The theory is based on the importance of the bottom vertical velocity in generating vorticity and shaping the baroclinic potential energy of the ACC. It explains the breaking of the f /h-constraint by baroclinicity and brings together in one equation the wind and buoyancy forcing of the current. The theory emphasizes the role of Ekman pumping and eddy diffusion of buoyancy to determine the transport. It also demonstrates that eddy viscosity effects are irrelevant in the barotropic vorticity balance and that friction arises via eddy diffusion of density. In this regime, the classical Stommel model of vorticity balance is revived where the bottom friction coefficient is replaced by K/λ 2 (with the GM coefficient K and the baroclinic Rossby radius λ) and a modified wind curl forcing appears.

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“…As the wind pattern is shifted to the south, less of the circulation is blocked by the continent of South America and the transport of the ACC is larger. The minor effect of the wind stress shift is due to the fact that the strength of the flow is determined by the component of the surface stress that is tangential to isopleths of planetary vorticity f/h [Johnson and Hill, 1975]. As the wind pattern is shifted, the strength of the circulation along each of these lines changes.…”

Section: Changes In Wind Positionmentioning

confidence: 99%

Effect of wind changes during the Last Glacial Maximum on the circulation in the Southern Ocean

Klinck¹,

Smith²

1993

Paleoceanography

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Present‐day surface wind stress climatology is manipulated to simulate wind conditions during the last glacial maximum. These estimated wind fields force a one‐layer, wind‐driven numerical model of the southern ocean to determine if a change in the strength of the surface wind stress can shift the location of the Antarctic Polar Front, which is part of the Antarctic Circumpolar Current. A change in the forcing by a factor of 0.5–2.0 results in a change in the speed of the flow by an identical factor with no change in position. However, if the present‐day wind climatology is shifted meridionally, there is a change in both strength of the circulation and spatial pattern. A shift of the wind stress of more than 5° of latitude is required to produce a shift in the location of the polar front.

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A three-dimensional model of the Southern Ocean with bottom topography

Cited by 16 publications

References 4 publications

The mean circulation of the southwestern Mediterranean Sea: Algerian Gyres

The mean circulation of the southwestern Mediterranean Sea: Algerian Gyres

Six circumpolar currents—on the forcing of the Antarctic Circumpolar Current by wind and mixing

Effect of wind changes during the Last Glacial Maximum on the circulation in the Southern Ocean

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