scholarly journals Direct observations of the Antarctic circumpolar current transport on the northern flank of the Kerguelen Plateau

2013 ◽  
Vol 118 (3) ◽  
pp. 1333-1348 ◽  
Author(s):  
G. M. Damerell ◽  
K. J. Heywood ◽  
D. P. Stevens
Keyword(s):  
Antarctic Circumpolar Current ◽  
Current Transport ◽  
Kerguelen Plateau ◽  
Northern Flank ◽  
Direct Observations ◽  
Circumpolar Current ◽  
The Antarctic

scholarly journals Time-Mean Flow as the Prevailing Contribution to the Poleward Heat Flux across the Southern Flank of the Antarctic Circumpolar Current: A Case Study in the Fawn Trough, Kerguelen Plateau

2013 ◽  
Vol 43 (3) ◽  
pp. 583-601 ◽  
Author(s):  
H. Sekma ◽  
Y.-H. Park ◽  
F. Vivier
Keyword(s):  
Heat Flux ◽  
Southern Ocean ◽  
Antarctic Circumpolar Current ◽  
Mean Flow ◽  
Kerguelen Plateau ◽  
The Mean ◽  
The Cross ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Southern Flank

Abstract The major mechanisms of the oceanic poleward heat flux in the Southern Ocean are still in debate. The long-standing belief stipulates that the poleward heat flux across the Antarctic Circumpolar Current (ACC) is mainly due to mesoscale transient eddies and the cross-stream heat flux by time-mean flow is insignificant. This belief has recently been challenged by several numerical modeling studies, which stress the importance of mean flow for the meridional heat flux in the Southern Ocean. Here, this study analyzes moored current meter data obtained recently in the Fawn Trough, Kerguelen Plateau, to estimate the cross-stream heat flux caused by the time-mean flow and transient eddies. It is shown that the poleward eddy heat flux in this southern part of the ACC is negligible, while that from the mean flow is overwhelming by two orders of magnitude. This is due to the unusual anticlockwise turning of currents with decreasing depth, which is associated with significant bottom upwelling engendered by strong bottom currents flowing over the sloping topography of the trough. The circumpolar implications of these local observations are discussed in terms of the depth-integrated linear vorticity budget, which suggests that the six topographic features along the southern flank of the ACC equivalent to the Fawn Trough case would yield sufficient poleward heat flux to balance the oceanic heat loss in the subpolar region. As eddy activity on the southern flank of the ACC is too weak to transport sufficient heat poleward, the nonequivalent barotropic structure of the mean flow in several topographically constricted passages should accomplish the required task.

scholarly journals Response of the antarctic circumpolar current transport to global warming in a coupled model

2002 ◽  
Vol 29 (24) ◽  
pp. 26-1-26-4 ◽  
Author(s):  
Daohua Bi ◽  
William F. Budd ◽  
Anthony C. Hirst ◽  
Xingren Wu
Keyword(s):  
Global Warming ◽  
Antarctic Circumpolar Current ◽  
Coupled Model ◽  
Current Transport ◽  
Circumpolar Current ◽  
The Antarctic

scholarly journals Thermohaline and Wind Forcing of a Circumpolar Channel withBlocked Geostrophic Contours

2002 ◽  
Vol 32 (9) ◽  
pp. 2520-2540 ◽  
Author(s):  
Daniel Borowski ◽  
Rüdiger Gerdes ◽  
Dirk Olbers
Keyword(s):  
Potential Energy ◽  
Antarctic Circumpolar Current ◽  
Drake Passage ◽  
Wind Forcing ◽  
Wind Effect ◽  
Current Transport ◽  
Leading Order ◽  
Meridional Gradient ◽  
Circumpolar Current ◽  
The Antarctic

Abstract The Antarctic Circumpolar Current is governed by unique dynamics. Because the latitude belt of Drake Passage is not zonally bounded by continents, the Sverdrup theory does not apply to the Antarctic Circumpolar Current. However, most of the geostrophic contours are blocked at Drake Passage, which provides an important dynamic constraint for the vorticity equation of the depth averaged flow. This study addresses the effects of thermohaline and wind forcing on the large-scale transport of a circumpolar current with blocked geostrophic contours. Various numerical experiments with three different idealized model geometries were conducted. Based on the results and theoretical arguments, the authors promote an indirect wind effect on the circumpolar current: while the direct effects of the wind in driving the circumpolar current through a vertical transfer of the applied wind stress are of minor importance, the wind does substantially influence the circumpolar current transport through its effects on the density field. This indirect wind effect is discussed in two steps. First, at the latitudes of the circumpolar current and longitudes where the geostrophic contours are blocked, the meridional gradient of the mass transport streamfunction is to leading order balanced by the meridional gradient of the baroclinic potential energy. This balance implies that the total transport is to leading order baroclinic and that the deep transport is small. For this statement, some theoretical arguments are offered. Second, a simplified analytical model is used to obtain the distribution of the baroclinic potential energy. Assuming an advective–diffusive balance for the densities in the deep downwelling northern branch of the Deacon cell, this model reproduces the qualitative dependence of the circumpolar current transport on the imposed wind and thermohaline forcing as well as on the turbulent diffusivities.

scholarly journals Mixing Variability in the Southern Ocean

2015 ◽  
Vol 45 (4) ◽  
pp. 966-987 ◽  
Author(s):  
Amelie Meyer ◽  
Bernadette M. Sloyan ◽  
Kurt L. Polzin ◽  
Helen E. Phillips ◽  
Nathaniel L. Bindoff
Keyword(s):  
Southern Ocean ◽  
Antarctic Circumpolar Current ◽  
Small Scale ◽  
Spatial And Temporal Variability ◽  
Transformation Rate ◽  
Intermediate Water ◽  
Kerguelen Plateau ◽  
Regional Variability ◽  
Circumpolar Current ◽  
The Antarctic

AbstractA key remaining challenge in oceanography is the understanding and parameterization of small-scale mixing. Evidence suggests that topographic features play a significant role in enhancing mixing in the Southern Ocean. This study uses 914 high-resolution hydrographic profiles from novel EM-APEX profiling floats to investigate turbulent mixing north of the Kerguelen Plateau, a major topographic feature in the Southern Ocean. A shear–strain finescale parameterization is applied to estimate diapycnal diffusivity in the upper 1600 m of the ocean. The indirect estimates of mixing match direct microstructure profiler observations made simultaneously. It is found that mixing intensities have strong spatial and temporal variability, ranging from O(10−6) to O(10−3) m2 s−1. This study identifies topographic roughness, current speed, and wind speed as the main factors controlling mixing intensity. Additionally, the authors find strong regional variability in mixing dynamics and enhanced mixing in the Antarctic Circumpolar Current frontal region. This enhanced mixing is attributed to dissipating internal waves generated by the interaction of the Antarctic Circumpolar Current and the topography of the Kerguelen Plateau. Extending the mixing observations from the Kerguelen region to the entire Southern Ocean, this study infers a large water mass transformation rate of 17 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) across the boundary of Antarctic Intermediate Water and Upper Circumpolar Deep Water in the Antarctic Circumpolar Current. This work suggests that the contribution of mixing to the Southern Ocean overturning circulation budget is particularly significant in fronts.

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