Systematic forcing of large-scale geophysical flows by eddy-topography interaction

1987 ◽  
Vol 184 ◽  
pp. 463-476 ◽  
Author(s):  
Greg Holloway
Keyword(s):  
Wave Propagation ◽  
Continental Shelf ◽  
Numerical Experiments ◽  
Antarctic Circumpolar Current ◽  
Large Scale ◽  
Geophysical Flows ◽  
Dominant Mechanism ◽  
Coastal Oceans ◽  
Circumpolar Current ◽  
Closure Theory

The interaction of eddies with variations in topography, together with a tendency for large-scale wave propagation, generates a systematic stress which acts upon large-scale mean flows. This stress resists the midlatitude tropospheric westerlies, resists the oceanic Antarctic Circumpolar Current, and may be a dominant mechanism in driving coastal undercurrents. Associated secondary circulation provides a systematic upwelling in coastal oceans, pumping deeper water onto continental shelf areas. The derivation rests in turbulence closure theory and is supported by numerical experiments.

scholarly journals Transport of warm Upper Circumpolar Deep Water onto the western Antarctic Peninsula continental shelf

Ocean Science ◽  
2012 ◽  
Vol 8 (4) ◽  
pp. 433-442 ◽  
Author(s):  
D. G. Martinson ◽  
D. C. McKee
Keyword(s):  
Continental Shelf ◽  
Antarctic Peninsula ◽  
Deep Water ◽  
Antarctic Circumpolar Current ◽  
Western Antarctic Peninsula ◽  
Dominant Mechanism ◽  
Circumpolar Deep Water ◽  
Marguerite Bay ◽  
Circumpolar Current ◽  
The Antarctic

Abstract. Five thermistor moorings were placed on the continental shelf of the western Antarctic Peninsula (between 2007 and 2010) in an effort to identify the mechanism(s) responsible for delivering warm Upper Circumpolar Deep Water (UCDW) onto the broad continental shelf from the Antarctic Circumpolar Current (ACC) flowing over the adjacent continental slope. Historically, four mechanisms have been suggested: (1) eddies shed from the ACC, (2) flow into the cross-shelf-cutting canyons with overflow onto the nominal shelf, (3) general upwelling, and (4) episodic advective diversions of the ACC onto the shelf. The mooring array showed that for the years of deployment, the dominant mechanism is eddies; upwelling may also contribute but to an unknown extent. Mechanism 2 played no role, though the canyons have been shown previously to channel UCDW across the shelf into Marguerite Bay. Mechanism 4 played no role independently, though eddies may be advected within a greater intrusion of the background flow.

scholarly journals Transport of warm upper circumpolar deep water onto the Western Antarctic Peninsula Continental Shelf

2011 ◽  
Vol 8 (6) ◽  
pp. 2479-2502 ◽  
Author(s):  
D. G. Martinson
Keyword(s):  
Continental Shelf ◽  
Antarctic Peninsula ◽  
Deep Water ◽  
Antarctic Circumpolar Current ◽  
Western Antarctic Peninsula ◽  
Dominant Mechanism ◽  
Circumpolar Deep Water ◽  
Marguerite Bay ◽  
Circumpolar Current ◽  
The Antarctic

Abstract. Five thermistor-moorings were placed on the continental shelf of the Western Antarctic Peninsula (between 2007 and 2010) in an effort to identify the mechanism(s) responsible for delivering warm Upper Circumpolar Deep Water (UCDW) onto the broad continental shelf from the Antarctic Circumpolar Current (ACC) flowing over the adjacent continental slope. Historically, four mechanisms have been suggested (or assumed): (1) eddies shed from the ACC, (2) flow into the cross-shelf-cutting canyons with overflow onto the nominal shelf, (3) general upwelling, and (4) episodic sweeping of ACC meanders over the shelf. The mooring array showed that for the years of deployment, the dominant mechanism is eddies; upwelling may also contribute but to an unknown extent. Mechanisms 2 and 4 played no role, though the canyons have been shown previously to channel UCDW across the shelf into Marguerite Bay.

scholarly journals Topographic Control of Southern Ocean Gyres and the Antarctic Circumpolar Current: A Barotropic Perspective

2019 ◽  
Vol 49 (12) ◽  
pp. 3221-3244 ◽  
Author(s):  
Ryan D. Patmore ◽  
Paul R. Holland ◽  
David R. Munday ◽  
Alberto C. Naveira Garabato ◽  
David P. Stevens ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Antarctic Circumpolar Current ◽  
Large Scale ◽  
Volume Transport ◽  
Topographic Features ◽  
Conservation Of Momentum ◽  
Ridge Width ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Ridge Geometry

AbstractIn the Southern Ocean the Antarctic Circumpolar Current is significantly steered by large topographic features, and subpolar gyres form in their lee. The geometry of topographic features in the Southern Ocean is highly variable, but the influence of this variation on the large-scale flow is poorly understood. Using idealized barotropic simulations of a zonal channel with a meridional ridge, it is found that the ridge geometry is important for determining the net zonal volume transport. A relationship is observed between ridge width and volume transport that is determined by the form stress generated by the ridge. Gyre formation is also highly reliant on the ridge geometry. A steep ridge allows gyres to form within regions of unblocked geostrophic (f/H) contours, with an increase in gyre strength as the ridge width is reduced. These relationships among ridge width, gyre strength, and net zonal volume transport emerge to simultaneously satisfy the conservation of momentum and vorticity.

scholarly journals THE MODEL STUDY OF THE WIND STRESS IMPACT TO THE INTERANNUAL VARIABILITY OF THE ANTARCTIC CIRCUMPOLAR CURRENT SOUTH OF AUSTRALIA

2019 ◽  
Vol 47 (2) ◽  
pp. 172-182 ◽  
Author(s):  
K.V. Lebedev
Keyword(s):  
Interannual Variability ◽  
Wind Stress ◽  
Numerical Experiments ◽  
Antarctic Circumpolar Current ◽  
Wind Forcing ◽  
Global Ocean ◽  
The Real ◽  
Key Factor ◽  
Circumpolar Current ◽  
The Antarctic

The interannual variability of the Antarctic Circumpolar Current (ACC) in the region south of Australia is studied on the base of numerical simulations performed with the use of the Argo-based model for Investigation of the Global Ocean (AMIGO). The model consists of a block for variational interpolation to a regular grid of Argo floats data and a block for model hydrodynamic adjustment of variationally interpolated fields. The mean ACC transport for the period of 2005–2014 through the Australia-Antarctica section was estimated at 178±6 Sv (1 Sv = 106m3/с-1). Additional numerical experiments were carried out in order to study the contribution of the wind forcing to the interannual variability of the ACC transport: the real thermohaline fields corresponding to the particular time period were replaced by climatic ones (1) and by replacing the real wind forcing data with the climatic ones (2). Analysis of the numerical experiments results has shown that the variable wind stress forcing is the key factor determining the interannual variability of the ACC transport through the Australia-Antarctica section.

scholarly journals Comparing Idealized and Complex Topographies in Quasigeostrophic Simulations of an Antarctic Circumpolar Current

2013 ◽  
Vol 43 (8) ◽  
pp. 1821-1837 ◽  
Author(s):  
Louis-Philippe Nadeau ◽  
David N. Straub ◽  
David M. Holland
Keyword(s):  
Antarctic Circumpolar Current ◽  
Large Scale ◽  
Drake Passage ◽  
Horizontal Resolution ◽  
Complex Topography ◽  
Form Drag ◽  
Scotia Ridge ◽  
Circumpolar Current ◽  
Recirculation Gyre ◽  
Realistic Topography

Abstract The circumpolar transport of a wind-driven quasigeostrophic Antarctic Circumpolar Current is considered. Simple theory suggests transport in a strongly forced regime—the focus of this study—is largely determined by a partitioning of the southward Sverdrup flux into Drake Passage latitudes: some streamlines feed a “basin contribution” to the circumpolar transport and others feed a large-scale recirculation gyre. Simulations assuming an idealized Scotia Ridge topography are considered to test for sensitivity to resolution. Considerable sensitivity to both vertical and horizontal resolution is found, and associated with this is a tight stationary eddy trapped on the western flank of the ridge. That is, this eddy is sensitive to resolution and exerts an influence that acts to reduce the circumpolar transport. Simulations using the Scotia Ridge–like topography are also compared to others using more realistic topography. In the idealized (ridge) topography experiments, there is only a single ridge against which topographic form drag can act to remove eastward momentum from the system; in the complex topography experiments, there are many. It is found that the experiments assuming realistic topography do not develop an analog to the single topographically trapped eddy prevalent in the Scotia Ridge topography simulations. Additionally, circumpolar transport in these simulations agrees better with the theory. Whether this agreement is simply fortuitous, however, is unclear. To address this, a series of simulations assumes topography that varies smoothly between the idealized ridge and realistic configurations.

scholarly journals Brief communication "On one mechanism of low frequency variability of the Antarctic Circumpolar Current"

2011 ◽  
Vol 18 (3) ◽  
pp. 361-365 ◽  
Author(s):  
O. G. Derzho ◽  
B. de Young
Keyword(s):  
Rossby Wave ◽  
Antarctic Circumpolar Current ◽  
Large Scale ◽  
Wave Train ◽  
Low Frequency ◽  
Wave Number ◽  
Mean Flow ◽  
Zonal Wave Number ◽  
Circumpolar Current ◽  
The Antarctic

Abstract. In this paper we present a simple analytical model for low frequency and large scale variability of the Antarctic Circumpolar Current (ACC). The physical mechanism of the variability is related to temporal and spatial variations of the cyclonic mean flow (ACC) due to circularly propagating nonlinear barotropic Rossby wave trains. It is shown that the Rossby wave train is a fundamental mode, trapped between the major fronts in the ACC. The Rossby waves are predicted to rotate with a particular angular velocity that depends on the magnitude and width of the mean current. The spatial structure of the rotating pattern, including its zonal wave number, is defined by the specific form of the stream function-vorticity relation. The similarity between the simulated patterns and the Antarctic Circumpolar Wave (ACW) is highlighted. The model can predict the observed sequence of warm and cold patches in the ACW as well as its zonal number.

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