Circumpolar structure and distribution of the Antarctic Circumpolar Current fronts: 2. Variability and relationship to sea surface height

2009 ◽  
Vol 114 (C11) ◽  
Author(s):  
Serguei Sokolov ◽  
Stephen R. Rintoul
Keyword(s):  
Antarctic Circumpolar Current ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Circumpolar Current ◽  
The Antarctic

Consistency of observed sea surface height changes, bottom pressure changes and temperature, salinity variations in a South Atlantic transect of the Antarctic Circumpolar Current

2020 ◽  
Author(s):  
Alisa Yakhontova ◽  
Roelof Rietbroek ◽  
Jens Schröter ◽  
Nadja Jonas ◽  
Christina Lück ◽  
...  
Keyword(s):  
Antarctic Circumpolar Current ◽  
Sea Surface Height ◽  
South Atlantic ◽  
Sea Surface ◽  
Ocean Bottom ◽  
Bottom Pressure ◽  
Satellite Gravimetry ◽  
Circumpolar Current ◽  
The Antarctic

<p>Improved estimates of temperature, salinity, and sea surface height changes are computed from radar altimetry, satellite gravimetry and Argo profiles, and validated by the in situ ocean bottom pressure measurements in a South Atlantic transect of the Antarctic Circumpolar current. Using satellite gravimetry and altimetry observations, separate contributions to the global sea level can be estimated, but a regional solution is more challenging. Furthermore, Argo derived steric sea level change suffers from spatio-temporal sampling problems, and some signals are not well captured, e.g. in the deeper ocean below 2000m, around the boundary currents, in the Arctic or in the shelf/coastal regions. Jointly processing radar altimetry, Argo and data from the Gravity Recovery and Climate Experiment (GRACE), would allow to correct the deficiencies of the individual datasets, and produce observation based estimates of consistent temperature, salinity and sea surface height changes. In order to pave the way for an advanced joint inversion scheme that additionally resolves for temperature and salinity, the observation equations are formulated which link the satellite observations to temperature and salinity at depth. Observations in the South Atlantic region are compared with simulations from the FESOM model in terms of variability and the model data is used to find the spatial coherence of the signals at the sites with the surrounding ocean. The experiment is performed in the Southern Atlantic Ocean, where the estimates can be validated using an array of in situ ocean bottom pressure observations.</p>

scholarly journals Eddy heat flux across the Antarctic Circumpolar Current estimated from sea surface height standard deviation

2017 ◽  
Vol 122 (8) ◽  
pp. 6947-6964 ◽  
Author(s):  
Annie Foppert ◽  
Kathleen A. Donohue ◽  
D. Randolph Watts ◽  
Karen L. Tracey
Keyword(s):  
Heat Flux ◽  
Standard Deviation ◽  
Antarctic Circumpolar Current ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Eddy Heat Flux ◽  
Circumpolar Current ◽  
The Antarctic

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.

Sea Surface Temperature Variability along the Path of the Antarctic Circumpolar Current

2006 ◽  
Vol 36 (7) ◽  
pp. 1317-1331 ◽  
Author(s):  
Ariane Verdy ◽  
John Marshall ◽  
Arnaud Czaja
Keyword(s):  
Antarctic Circumpolar Current ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Sea Surface ◽  
Heat Advection ◽  
Surface Heat Fluxes ◽  
Sst Variability ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Sst Anomalies

Abstract The spatial and temporal distributions of sea surface temperature (SST) anomalies in the Antarctic Circumpolar Current (ACC) are investigated, using monthly data from the NCEP–NCAR reanalysis for the period 1980–2004. Patterns of atmospheric forcing are identified in observations of sea level pressure and air–sea heat fluxes. It is found that a significant fraction of SST variability in the ACC can be understood as a linear response to surface forcing by the Southern Annular Mode (SAM) and remote forcing by ENSO. The physical mechanisms rely on the interplay between atmospheric variability and mean advection by the ACC. SAM and ENSO drive a low-level anomalous circulation pattern localized over the South Pacific Ocean, inducing surface heat fluxes and Ekman heat advection anomalies. A simple model of SST propagating in the ACC, forced with heat fluxes estimated from the reanalysis, suggests that surface heat fluxes and Ekman heat advection are equally important in driving the observed SST variability. Further diagnostics indicate that SST anomalies, generated mainly upstream of Drake Passage, are subsequently advected by the ACC and damped after a couple of years. It is suggested that SST variability along the path of the ACC is largely a passive response of the oceanic mixed layer to atmospheric forcing.

scholarly journals Reshaping the Antarctic Circumpolar Current via Antarctic Bottom Water Export

2017 ◽  
Vol 47 (10) ◽  
pp. 2577-2601 ◽  
Author(s):  
Andrew L. Stewart ◽  
Andrew McC. Hogg
Keyword(s):  
Antarctic Circumpolar Current ◽  
Bottom Water ◽  
Channel Model ◽  
Meridional Overturning Circulation ◽  
Sea Surface ◽  
Momentum Balance ◽  
Antarctic Bottom Water ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Zonal Momentum

AbstractZonal momentum input into the Antarctic Circumpolar Current (ACC) by westerly winds is ultimately removed via topographic form stress induced by large bathymetric features that obstruct the path of the current. These bathymetric features also support the export of Antarctic Bottom Water (AABW) across the ACC via deep, geostrophically balanced, northward flows. These deep geostrophic currents modify the topographic form stress, implying that changes in AABW export will alter the ocean bottom pressure and require a rearrangement of the ACC in order to preserve its zonal momentum balance. A conceptual model of the ACC momentum balance is used to derive a relationship between the volume export of AABW and the shape of the sea surface across the ACC’s standing meanders. This prediction is tested using an idealized eddy-resolving ACC/Antarctic shelf channel model that includes both the upper and lower cells of the Southern Ocean meridional overturning circulation, using two different topographic configurations to obstruct the flow of the ACC. Eliminating AABW production leads to a shallowing of the sea surface elevation within the standing meander. To quantify this response, the authors introduce the “surface-induced topographic form stress,” the topographic form stress that would result from the shape of the sea surface if the ocean were barotropic. Eliminating AABW production also reduces the magnitude of the eddy kinetic energy generated downstream of the meander and the surface speed of the ACC within the meander. These findings raise the possibility that ongoing changes in AABW export may be detectable via satellite altimetry.

scholarly journals Meridional displacement of the Antarctic Circumpolar Current

2014 ◽  
Vol 372 (2019) ◽  
pp. 20130273 ◽  
Author(s):  
Sarah T. Gille
Keyword(s):  
Antarctic Circumpolar Current ◽  
Large Scale ◽  
Southern Oscillation ◽  
Southern Annular Mode ◽  
Sea Surface Height ◽  
Sea Surface ◽  
Altimeter Data ◽  
Eddy Heat Transport ◽  
Circumpolar Current

Observed long-term warming trends in the Southern Ocean have been interpreted as a sign of increased poleward eddy heat transport or of a poleward displacement of the entire Antarctic Circumpolar Current (ACC) frontal system. The two-decade-long record from satellite altimetry is an important source of information for evaluating the mechanisms governing these trends. While several recent studies have used sea surface height contours to index ACC frontal displacements, here altimeter data are instead used to track the latitude of mean ACC transport. Altimetric height contours indicate a poleward trend, regardless of whether they are associated with ACC fronts. The zonally averaged transport latitude index shows no long-term trend, implying that ACC meridional shifts determined from sea surface height might be associated with large-scale changes in sea surface height more than with localized shifts in frontal positions. The transport latitude index is weakly sensitive to the Southern Annular Mode, but is uncorrelated with El Niño/Southern Oscillation.

scholarly journals Nonlinear Differential Equations Modeling the Antarctic Circumpolar Current

2021 ◽  
Vol 23 (4) ◽  
Author(s):  
Jifeng Chu ◽  
Kateryna Marynets
Keyword(s):  
Fixed Point ◽  
Differential Equations ◽  
Boundary Conditions ◽  
Topological Degree ◽  
Antarctic Circumpolar Current ◽  
Fixed Point Theorems ◽  
Nonlinear Differential Equations ◽  
Existence Results ◽  
Circumpolar Current ◽  
The Antarctic

AbstractThe aim of this paper is to study one class of nonlinear differential equations, which model the Antarctic circumpolar current. We prove the existence results for such equations related to the geophysical relevant boundary conditions. First, based on the weighted eigenvalues and the theory of topological degree, we study the semilinear case. Secondly, the existence results for the sublinear and superlinear cases are proved by fixed point theorems.

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