Dynamical budgets of the Antarctic Circumpolar Current using ocean general-circulation models

Grezio, Anita; Wells, N. C.; Ivchenko, Vladimir; Cuevas, B. A. de

doi:10.1256/qj.03.213

Cited by 9 publications

(15 citation statements)

References 70 publications

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“…The smaller transport at Drake Passage in G22 (141 Sv compared to 154 Sv in G04) is therefore a consequence of the PS topography. This is consistent with former studies, which demonstrated how crucial the bottom topography is to establish the momentum balance of the ACC (Rintoul et al 2002;Grezio et al 2005).…”

Section: Global Analysissupporting

confidence: 93%

Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy-permitting resolution

et al. 2006

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Section: Global Analysissupporting

confidence: 93%

Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy-permitting resolution

et al. 2006

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“…Grezio et al . [] noted a similar division in the mean form stress signal between deep (3722–4989 m) and very deep (4989–5500 m) regimes in OCCAM; topographic form stress was of the same order of magnitude as wind stress in the deep regime, but an order of magnitude smaller in the very deep regime. These authors too noted that at some latitudes, the sign of the topographic form stress in the very deep regime was the same as the wind stress.…”

Section: Resultsmentioning

confidence: 99%

“…Grezio et al . [] showed that topographic form stress balances wind stress in the zonal mean in both the 1/4°, 36‐level OCCAM project model and the 20‐level Parallel Ocean Program (POP) model as well, with a small but significant contribution from eddy flux divergence in both models.…”

Section: Introductionmentioning

confidence: 81%

“…The zonal integral has also been explored in high resolution general circulation models as well; in the 1/28 by 1/48, 32-level Fine Resolution Antarctic Model (FRAM), topographic form stress was shown to balance wind stress in the zonal average in the unblocked latitudes by Killworth and Nanneh [1994] and Stevens and Ivchenko [1997], and along streamlines in the ACC latitudes by Ivchenko et al [1996]. Grezio et al [2005] showed that topographic form stress balances wind stress in the zonal mean in both the 1/48, 36-level OCCAM project model and the 20-level Parallel Ocean Program (POP) model as well, with a small but significant contribution from eddy flux divergence in both models.…”

Section: Introductionmentioning

confidence: 99%

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Topographic form stress in the Southern Ocean State Estimate

2015

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We diagnose the Southern Ocean momentum balance in a 6 year, eddy‐permitting state estimate of the Southern Ocean. We find that 95% of the zonal momentum input via wind stress at the surface is balanced by topographic form stress across ocean ridges, while the remaining 5% is balanced via bottom friction and momentum flux divergences at the northern and southern boundaries of the analysis domain. While the time‐mean zonal wind stress field exhibits a relatively uniform spatial distribution, time‐mean topographic form stress concentrates at shallow ridges and across the continents that lie within the Antarctic Circumpolar Current (ACC) latitudes; nearly 40% of topographic form stress occurs across South America, while the remaining 60% occurs across the major submerged ridges that underlie the ACC. Topographic form stress can be divided into shallow and deep regimes: the shallow regime contributes most of the westward form stress that serves as a momentum sink for the ACC system, while the deep regime consists of strong eastward and westward form stresses that largely cancel in the zonal integral. The time‐varying form stress signal, integrated longitudinally and over the ACC latitudes, tracks closely with the wind stress signal integrated over the same domain; at zero lag, 88% of the variance in the 6 year form stress time series can be explained by the wind stress signal, suggesting that changes in the integrated wind stress signal are communicated via rapid barotropic response down to the level of bottom topography.

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“…Recently the momentum balance between wind stress and the bottom pressure difference was again confirmed by Grezio et al (2006) who analyzed the outputs of two OGCM simulations with the ACC transports being in a realistic range (152 and 134 Sv in the cases of a horizontal resolution of 0.25…”

Section: Regional Statisticsmentioning

confidence: 84%

Maintenance of the mean kinetic energy in the global ocean by the barotropic and baroclinic energy routes: the roles of JEBAR and Ekman dynamics

2011

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In order to determine the maintenance mechanisms of the currents of the global ocean, this study investigates the budget of the annual mean kinetic energy (KE) in a high-resolution (0.1• × 0.1 • ) semi-global ocean simulation. The analysis is based on a separation of the mean KE using the barotropic (i.e., depthaveraged) and baroclinic (the residual) components of velocity. The barotropic and baroclinic KEs dominate in higher and lower latitudes, respectively, with their global average being comparable to each other. The working rates of wind forcing on the barotropic and baroclinic circulations in the global ocean are 243 and 747 gigawatts, respectively. This study presents at least three new results for the budget of the barotropic KE. Firstly, an energy diagram is rederived to show that the work of the barotropic component of the horizontal pressure gradient (HPG) is connected to the work related to the joint effect of baroclinicity and bottom relief (JEBAR), and then to the budget of potential energy (PE). Secondly, the model analysis shows that the globally averaged work of the barotropic HPG (which is connected to the work related to JEBAR and then to the budget of the PE) is nearly zero. This indicates that the wind-and buoyancy-induced barotropic circulations in the global ocean are of the same strength with opposite sign. Thirdly, it is found that the work of the wind forcing on the barotropic component of the simulated Antarctic Circumpolar Current (ACC) is canceled by the combined effect, in equal measure, of the work of the barotropic HPG and the work of dissipative processes for mean KE. This result makes a significant contribution to the discussion on the depth-integrated momentum balance of the ACC. The barotropic KE is dissipated by the effects of bottom frictional stress, lateral frictional stress, and the Reynolds stress, of which more than half is attributed to an unexpectedly large contribution from biharmonic horizontal friction. Future studies should pay more attention to the role of biharmonic friction used in high-resolution numerical models.

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Dynamical budgets of the Antarctic Circumpolar Current using ocean general-circulation models

Cited by 9 publications

References 70 publications

Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy-permitting resolution

Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy-permitting resolution

Topographic form stress in the Southern Ocean State Estimate

Maintenance of the mean kinetic energy in the global ocean by the barotropic and baroclinic energy routes: the roles of JEBAR and Ekman dynamics

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