Exchanges between hemispheres and gyres : a direct approach to the mean circulation of the equatorial Pacific

Wijffels, Susan E.

doi:10.1575/1912/5526

Cited by 38 publications

(35 citation statements)

References 38 publications

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“…The use of conservation equations in terms of property anomalies (e.g., McDougall, 1991a;Wijffels, 1993) rather than full property values themselves-but based upon making explicit the necessary assumptions concerning the error covariance between mass constraints and property constraints (Wunsch, 1996, p.273).…”

Section: Overviewmentioning

confidence: 99%

“…I used here the so called "inverse box model" described by Wunsch (1978) and subsequently used in various studies (e.g., Wunsch, 1982;Rintoul and Wunsch, 1991;Wijffels, 1993;Macdonald and Wunsch, 1996;Tsimplis et aI., 1998, Top-to-Bottom within individual layers Mass yes yes Thermodynamic energy (heat) no below surface Salinity yes yes Silica yes no "NO" (9.1 NO a +0 2 ) no no "PO" (170 PO,! +0 2 ) no below surface Table 1.2: Conservation constraints for the standard solution.…”

Section: Model Formulationmentioning

confidence: 99%

“…As a result, the original full property equations produce an ill-conditioned matrix (e.g., McDougall, 1989;Wijffels, 1993). To better condition the system, one can subtract the mass divergence times the average property concentration for each layer from each tracer conservation equation.…”

Section: Anomaly Equationsmentioning

confidence: 99%

“…The main test of consistency comes from the fact that the residuals of all conservation equation are indistinguishable from zero within a posteriori error bars. Wijffels (1993) weighted her anomaly equations in a similar way, but assumed that the salinity variations were dominated by vertical differences. Because we have no information on the noise in vertical exchanges, it is not clear whether this approach is more appropriate than ours.…”

Section: Nvs(xz) =Nv(xz) X S(xz)mentioning

confidence: 99%

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Large scale oceanic circulation and fluxes of freshwater, heat, nutrients and oxygen

Ganachaud¹

1999

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Section: Overviewmentioning

confidence: 99%

Section: Model Formulationmentioning

confidence: 99%

Section: Anomaly Equationsmentioning

confidence: 99%

Section: Nvs(xz) =Nv(xz) X S(xz)mentioning

confidence: 99%

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Large scale oceanic circulation and fluxes of freshwater, heat, nutrients and oxygen

Ganachaud¹

1999

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“…Fo• instance, in the Pacific Ocean, about 10 x 10 a m s s -x of water from the southern hemisphere must cross the equator to feed the Indonesian throughflow [Gordon et al, 1999]. This water cycles through the Pacific STC on its way north [Wijffels, 1993].…”

mentioning

confidence: 99%

The Pacific Ocean Subtropical cell surface limb

Johnson

2001

Geophysical Research Letters

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Inter‐hemispheric oceanic exchange

Nof

Борисов

1998

Quart J Royal Meteoro Soc

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SUMMARYThe exchange of water between hemispheres is examined theoretically by looking at the behaviour of continuous (double frontal) abyssal currents situated on the bottom of a (parabolic) meridional channel. We used a reduced-gravity (fluid) model with an active lower layer on the bottom of the channel, and a passive infinitely deep upper layer on the top. The topography is the agent responsible for forcing the current across the equator. We first examined analytically the nonlinear, steady, frictionless case and, as a second step, we considered a nonlinear numerical simulation (of the Bleck and Boudra type). We then compared the results of these two (fluid) models to each other and to the solid-balls model of Borisov and Nof which examined the migration of particles in the same cross-equatorial channel.All three models show that, in general, the current (or a 'cloud' of solid particles) advances gradually toward the equator without much change to its structure. Upon reaching the vicinity of the equator, the current width (or the distance between neighbouring balls) decreases dramatically. The current (or cloud) then turns eastward, flows rapidly downslope, and rises on the eastern side. The flow (or cloud) ultimately splits into two parts, one progressing northward and the other recirculating and advancing southward.Remarkably good agreement is found between the detailed solid-particles analysis and the new numerical fluid simulations, indicating that the inter-hemispheric exchange is primarily an inertial process that depends mainly on the channel geometry. It is shown that the partition of mass flux between the two hemispheres depends on the way that the solid particles, or the current-jet, impinge on the eastern flank of the channel. In contrast to the very good agreement between the solid balls and the fluid simulations, poor agreement was found between the detailed analytical prediction for the cross-equatorial transport and the numerical solution (even when the viscosity was as small as we could use for numerical stability). However, the analytical solution does give the correct prediction for the position of the resulting currents and their general behaviour. It is argued that the disagreement between the analytically calculated fluid mass transports (which, in contrast to the balls, is subject to a potential-vorticity constraint) and the numerical computations is due to the alteration of potential vorticity. Specifically, the friction alters the potential vorticity of the flow and prevents it from acting as a constraint to the crossing. Though crucial to the crossing, the role of friction is, therefore, passive. It merely allows the fluid to alter its potential vorticity in such a manner that the flow can adapt to the crossing pattern imposed by the geometry.It is suggested that the observed recirculation of Antarctic Bottom Water in the vicinity of the equatorial Atlantic may be a result of our splitting process.

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Exchanges between hemispheres and gyres : a direct approach to the mean circulation of the equatorial Pacific

Cited by 38 publications

References 38 publications

Large scale oceanic circulation and fluxes of freshwater, heat, nutrients and oxygen

Large scale oceanic circulation and fluxes of freshwater, heat, nutrients and oxygen

The Pacific Ocean Subtropical cell surface limb

Inter‐hemispheric oceanic exchange

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