scholarly journals Heat fluxes across the Antarctic Circumpolar Current in Drake Passage: Mean flow and eddy contributions

2014 ◽  
Vol 119 (9) ◽  
pp. 6381-6402 ◽  
Author(s):  
Ramiro Ferrari ◽  
Christine Provost ◽  
Young-Hyang Park ◽  
Nathalie Sennéchael ◽  
Zoé Koenig ◽  
...  
Keyword(s):  
Antarctic Circumpolar Current ◽  
Drake Passage ◽  
Heat Fluxes ◽  
Mean Flow ◽  
Circumpolar Current ◽  
The Antarctic

scholarly journals Estimates of Eddy Heat Flux Crossing the Antarctic Circumpolar Current from Observations in Drake Passage

2016 ◽  
Vol 46 (7) ◽  
pp. 2103-2122 ◽  
Author(s):  
D. Randolph Watts ◽  
Karen L. Tracey ◽  
Kathleen A. Donohue ◽  
Teresa K. Chereskin
Keyword(s):  
Heat Flux ◽  
Heat Transport ◽  
Antarctic Circumpolar Current ◽  
Baroclinic Instability ◽  
Drake Passage ◽  
Heat Fluxes ◽  
Poleward Heat Transport ◽  
Eddy Heat Flux ◽  
Circumpolar Current ◽  
The Antarctic

AbstractThe 4-yr measurements by current- and pressure-recording inverted echo sounders in Drake Passage produced statistically stable eddy heat flux estimates. Horizontal currents in the Antarctic Circumpolar Current (ACC) turn with depth when a depth-independent geostrophic current crosses the upper baroclinic zone. The dynamically important divergent component of eddy heat flux is calculated. Whereas full eddy heat fluxes differ greatly in magnitude and direction at neighboring locations within the local dynamics array (LDA), the divergent eddy heat fluxes are poleward almost everywhere. Case studies illustrate baroclinic instability events that cause meanders to grow rapidly. In the southern passage, where eddy variability is weak, heat fluxes are weak and not statistically significant. Vertical profiles of heat flux are surface intensified with ~50% above 1000 m and uniformly distributed with depth below. Summing poleward transient eddy heat transport across the LDA of −0.010 ± 0.005 PW with the stationary meander contribution of −0.004 ± 0.001 PW yields −0.013 ± 0.005 PW. A comparison metric, −0.4 PW, represents the total oceanic heat loss to the atmosphere south of 60°S. Summed along the circumpolar ACC path, if the LDA heat flux occurred at six “hot spots” spanning similar or longer path segments, this could account for 20%–70% of the metric, that is, up to −0.28 PW. The balance of ocean poleward heat transport along the remaining ACC path should come from weak eddy heat fluxes plus mean cross-front temperature transports. Alternatively, the metric −0.4 PW, having large uncertainty, may be high.

scholarly journals Direct Estimate of Lateral Eddy Diffusivity Upstream of Drake Passage

2014 ◽  
Vol 44 (10) ◽  
pp. 2593-2616 ◽  
Author(s):  
Ross Tulloch ◽  
Raffaele Ferrari ◽  
Oliver Jahn ◽  
Andreas Klocker ◽  
Joseph LaCasce ◽  
...  
Keyword(s):  
Antarctic Circumpolar Current ◽  
Model Simulation ◽  
Phase Speed ◽  
Drake Passage ◽  
Eddy Diffusivity ◽  
Flow Speed ◽  
Mean Flow ◽  
Direct Estimate ◽  
Circumpolar Current ◽  
The Antarctic

Abstract The first direct estimate of the rate at which geostrophic turbulence mixes tracers across the Antarctic Circumpolar Current is presented. The estimate is computed from the spreading of a tracer released upstream of Drake Passage as part of the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES). The meridional eddy diffusivity, a measure of the rate at which the area of the tracer spreads along an isopycnal across the Antarctic Circumpolar Current, is 710 ± 260 m2 s−1 at 1500-m depth. The estimate is based on an extrapolation of the tracer-based diffusivity using output from numerical tracers released in a one-twentieth of a degree model simulation of the circulation and turbulence in the Drake Passage region. The model is shown to reproduce the observed spreading rate of the DIMES tracer and suggests that the meridional eddy diffusivity is weak in the upper kilometer of the water column with values below 500 m2 s−1 and peaks at the steering level, near 2 km, where the eddy phase speed is equal to the mean flow speed. These vertical variations are not captured by ocean models presently used for climate studies, but they significantly affect the ventilation of different water masses.

Medium-scale heat fluxes across the Antarctic Circumpolar Current in the Drake Passage and western Scotia Sea

1996 ◽  
Vol 8 (4) ◽  
pp. 369-378
Author(s):  
Alberto R. Piola ◽  
Monica B. Grasselli
Keyword(s):  
Antarctic Circumpolar Current ◽  
Heat Content ◽  
Drake Passage ◽  
Polar Front ◽  
Heat Fluxes ◽  
Scotia Sea ◽  
Medium Scale ◽  
Scale Temperature ◽  
Circumpolar Current ◽  
The Antarctic

Closely spaced continuous temperature profiles from expendable bathythermographs launched along two sections across the Drake Passage and western Scotia Sea in the summer 1981–1982 are used to examine the vertical medium-scale (∼10–100 m) temperature fine structure. The large-scale temperature structure across the frontal regimes characteristic of the Antarctic Circumpolar Current and the cross-frontal structure of the upper ocean are discussed. In the Drake Passage the heat content drops about 0.5 × 102 Kcal cm−2 (2 × 109 J m−2) across the Subantarctic Zone and 0.9 × 102 Kcal cm−2 (3.6 − 109 J m−2) across the Polar Front. In the Scotia Sea the heat content changes across the front are not as prominent. The statistical model of Joyce (1977) is used to quantify the heat fluxes across the fronts produced by the medium-scale temperature interleaving. In the Drake Passage the estimated heat flux is 0.32 × 10−3 °C m s−1 (1.3 × 103 W m−2) across the Subantarctic Front and 0.46 × 10−3 °C m s−1 (1.9 × 103 W m−2) across the Polar Front. In the Scotia Sea the estimated heat flux is larger in the Polar Front reaching 0.71 × 10−3 °C m s−1 (2.9 × 103 W m−2). The medium-scale fine structure heat fluxes are about 10% of the existing estimates of the mesoscale eddy heat fluxes and comparable to heat fluxes associated with the meridional flow of deep and bottom waters across the Antarctic Circumpolar Current.

scholarly journals Intrinsic variability of the Antarctic Circumpolar Current system: low- and high-frequency fluctuations of the Argentine Basin flow

Ocean Science ◽  
2014 ◽  
Vol 10 (2) ◽  
pp. 201-213 ◽  
Author(s):  
G. Sgubin ◽  
S. Pierini ◽  
H. A. Dijkstra
Keyword(s):  
High Frequency ◽  
Antarctic Circumpolar Current ◽  
Current System ◽  
Low Frequency ◽  
Drake Passage ◽  
Ocean Model ◽  
Intrinsic Variability ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Argentine Basin

Abstract. In this paper, the variability of the Antarctic Circumpolar Current system produced by purely intrinsic nonlinear oceanic mechanisms is studied through a sigma-coordinate ocean model, implemented in a large portion of the Southern Ocean at an eddy-permitting resolution under steady surface heat and momentum fluxes. The mean transport through the Drake Passage and the structure of the main Antarctic Circumpolar Current fronts are well reproduced by the model. Intrinsic variability is found to be particularly intense in the Subantarctic Front and in the Argentine Basin, on which further analysis is focused. The low-frequency variability at interannual timescales is related to bimodal behavior of the Zapiola Anticyclone, with transitions between a strong and collapsed anticyclonic circulation in substantial agreement with altimeter observations. Variability on smaller timescales shows clear evidence of topographic Rossby-wave propagation along the eastern and southern flanks of the Zapiola Rise and of mesoscale eddies, also in agreement with altimeter observations. The analysis of the relationship between the low- and high-frequency variability suggests possible mechanisms of mutual interaction.

scholarly journals Coupling Influences of ENSO and PDO on the Inter-Decadal SST Variability of the ACC around the Western South Atlantic

2019 ◽  
Vol 11 (18) ◽  
pp. 4853
Author(s):  
You-Lin Wang ◽  
Yu-Chen Hsu ◽  
Chung-Pan Lee ◽  
Chau-Ron Wu
Keyword(s):  
Antarctic Circumpolar Current ◽  
Water Mass ◽  
Southern Oscillation ◽  
Drake Passage ◽  
South Atlantic ◽  
Sst Variability ◽  
The Pacific ◽  
Circumpolar Current ◽  
The Antarctic

The Antarctic Circumpolar Current (ACC) plays an important role in the climate as it balances heat energy and water mass between the Pacific and Atlantic Oceans through the Drake Passage. However, because the historical measurements and observations are extremely limited, the decadal and long-term variations of the ACC around the western South Atlantic Ocean are rarely studied. By analyzing reconstructed sea surface temperatures (SSTs) in a 147-year period (1870–2016), previous studies have shown that SST anomalies (SSTAs) around the Antarctic Peninsula and South America had the same phase change as the El Niño Southern Oscillation (ENSO). This study further showed that changes in SSTAs in the regions mentioned above were enlarged when the Pacific Decadal Oscillation (PDO) and the ENSO were in the same warm or cold phase, implying that changes in the SST of higher latitude oceans could be enhanced when the influence of the ENSO is considered along with the PDO.

Jets of the Antarctic Circumpolar Current in the Drake Passage Based on Hydrographic Section Data

2020 ◽  
Author(s):  
Roman Tarakanov ◽  
Alexander Gritsenko
Keyword(s):  
Antarctic Circumpolar Current ◽  
Basic Research ◽  
Drake Passage ◽  
Section Data ◽  
Temporal And Spatial ◽  
Circumpolar Current ◽  
Basic Research Grant ◽  
The Antarctic ◽  
Jet Structure ◽  
Satellite Altimetry Data

<p>We have analyzed the fine structure of Antarctic Circumpolar Current jets in the Drake Passage based on CTD and SADCP measurements over two hydrographic sections in January 2010 and October–November 2011. Eleven jets with a local horizontal velocity maximum were revealed in 2010, and nine jets were in 2011. These individual jets were various combinations of 12 jets of the Antarctic Circumpolar Current, which we revealed earlier in the region south of Africa on the basis of the section data in December 2009. Daily satellite altimetry data available at http://www.aviso.altimetry.fr were also used to interpret the synoptic patterns of currents over the sections. These results allow us to suggest that the multi-jet structure with a number of jets exceeding nine reported by Sokolov&Rintoul, 2009 is common for the entire circumpolar circle and even for regions with significant contraction of the ACC, such as the Drake Passage. However, the question about the number of jets and its temporal and spatial permanency remains open. Investigation was supported by Russian Foundation of Basic Research grant No 18-05-00283.</p>

scholarly journals Multiple Jets of the Antarctic Circumpolar Current South of Australia*

2007 ◽  
Vol 37 (5) ◽  
pp. 1394-1412 ◽  
Author(s):  
Serguei Sokolov ◽  
Stephen R. Rintoul
Keyword(s):  
Southern Ocean ◽  
Antarctic Circumpolar Current ◽  
Sea Surface ◽  
Mean Flow ◽  
Nonlinear Fitting ◽  
Fitting Procedure ◽  
Multiple Jets ◽  
Gradient Fields ◽  
Circumpolar Current ◽  
The Antarctic

Abstract Maps of the gradient of sea surface height (SSH) and sea surface temperature (SST) reveal that the Antarctic Circumpolar Current (ACC) consists of multiple jets or frontal filaments. The braided and patchy nature of the gradient fields seems at odds with the traditional view, derived from hydrographic sections, that the ACC is made up of three continuous circumpolar fronts. By applying a nonlinear fitting procedure to 638 weekly maps of SSH gradient (∇SSH), it is shown that the distribution of maxima in ∇SSH (i.e., fronts) is strongly peaked at particular values of absolute SSH (i.e., streamlines). The association between the jets and particular streamlines persists despite strong topographic and eddy–mean flow interactions, which cause the jets to merge, diverge, and fluctuate in intensity along their path. The SSH values corresponding to each frontal branch are nearly constant over the sector of the Southern Ocean between 100°E and 180°. The front positions inferred from SSH agree closely with positions inferred from hydrographic sections using traditional water mass criteria. Recognition of the multiple branches of the Southern Ocean fronts helps to reconcile differences between front locations determined by previous studies. Weekly maps of SSH are used to characterize the structure and variability of the ACC fronts and filaments. The path, width, and intensity of the frontal branches are influenced strongly by the bathymetry. The “meander envelopes” of the fronts are narrow on the northern slope of topographic ridges, where the sloping topography reinforces the β effect, and broader over abyssal plains.

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