scholarly journals Study of the Antarctic Circumpolar Current via the Shallow Water Large Scale Modelling

2022 ◽  
Author(s):  
K. Marynets
Keyword(s):  
Boundary Value Problem ◽  
Ocean Circulation ◽  
Antarctic Circumpolar Current ◽  
Large Scale ◽  
Global Climate ◽  
Boundary Value ◽  
Global Ocean ◽  
Uniqueness Of Solutions ◽  
Circumpolar Current ◽  
The Antarctic

Abstract. This paper proposes a modelling of the Antarctic Circumpolar Current (ACC) by means of a two-point boundary value problem. As the major means of exchange of water between the great ocean basins (Atlantic, Pacific and Indian), the ACC plays a highly important role in the global climate. Despite its importance, it remains one of the most poorly understood components of global ocean circulation. We present some recent results on the existence and uniqueness of solutions of a two-point nonlinear boundary value problem that arises in the modeling of the flow of the (ACC) (see discussions in [4-9]).

scholarly journals The Effect of the Kerguelen Plateau on the Ocean Circulation

2016 ◽  
Vol 46 (11) ◽  
pp. 3385-3396 ◽  
Author(s):  
Jinbo Wang ◽  
Matthew R. Mazloff ◽  
Sarah T. Gille
Keyword(s):  
Southern Ocean ◽  
Ocean Circulation ◽  
Antarctic Circumpolar Current ◽  
Large Scale ◽  
Pressure Field ◽  
Global Ocean ◽  
Kerguelen Plateau ◽  
Local Pressure ◽  
Circumpolar Current ◽  
The Antarctic

AbstractThe Kerguelen Plateau is a major topographic feature in the Southern Ocean. Located in the Indian sector and spanning nearly 2000 km in the meridional direction from the polar to the subantarctic region, it deflects the eastward-flowing Antarctic Circumpolar Current and influences the physical circulation and biogeochemistry of the Southern Ocean. The Kerguelen Plateau is known to govern the local dynamics, but its impact on the large-scale ocean circulation has not been explored. By comparing global ocean numerical simulations with and without the Kerguelen Plateau, this study identifies two major Kerguelen Plateau effects: 1) The plateau supports a local pressure field that pushes the Antarctic Circumpolar Current northward. This process reduces the warm-water transport from the Indian to the Atlantic Ocean. 2) The plateau-generated pressure field shields the Weddell Gyre from the influence of the warmer subantarctic and subtropical waters. The first effect influences the strength of the Antarctic Circumpolar Current and the Agulhas leakage, both of which are important elements in the global thermohaline circulation. The second effect results in a zonally asymmetric response of the subpolar gyres to Southern Hemisphere wind forcing.

Investigating the Dynamics of the Pacific Antarctic Circumpolar Current – Initial Results from International Ocean Discovery Program Expedition 383 (DYNAPACC)

2020 ◽  
Author(s):  
Frank Lamy ◽  
Gisela Winckler ◽  
Carlos Zarikian ◽  
Expedition 383 Scientists
Keyword(s):  
Antarctic Circumpolar Current ◽  
Global Climate ◽  
South Pacific ◽  
Global Ocean ◽  
Sedimentary Sequences ◽  
The Pacific ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Central South ◽  
Chilean Margin

<p>The Antarctic Circumpolar Current (ACC) is the world’s strongest zonal current system that connects all three major basins of the global ocean, and therefore integrates, forces and responds to global climate variability. In contrast to the Atlantic and Indian sectors of the ACC, and with the exception of drill cores from the Antarctic continental margin and off New Zealand, the Pacific sector of the ACC lacks information on its Cenozoic paleoceanography from deep-sea drilling records.</p><p>To advance our knowledge and understanding of Miocene to Holocene atmosphere-ocean-cryosphere dynamics in the Pacific and their implications for regional and global climate and atmospheric CO<sub>2</sub>, IODP Expedition 383 recovered sedimentary sequences at: (1) Three sites located in the central South Pacific (Sites U1539, U1540 and U1541); (2) two sites at the Chilean Margin (U1542, U1544); and (3) one site from the hemipelagic eastern South Pacific (U1543) close to the entrance to the Drake Passage. Age control based on magneto and bio-stratigraphically constrained orbital tuning of physical properties in the Plio-Pleistocene sediments is remarkable, with Sites U1541 and U1543 extending the record back to the late Miocene, and Site U1540 to the earliest Pliocene. Pleistocene sedimentary sequences with high sedimentation rates in the order of 40 cm/kyr were drilled in the Central South Pacific (U1539) and along the Chilean Margin. Taken together, the sites represent a depth transect from ~1100 m at the Chilean margin (U1542) to ~4070 m in the Central South Pacific (U1539), and allow reconstructing changes in the vertical structure of the ACC – a key issue for understanding the role of the Southern Ocean in the global carbon cycle- to be investigated. The sites are located at latitudes and water depths where sediments will allow the application of a wide range of siliciclastic, carbonate, and opal-based proxies to address our objectives of reconstructing, with unprecedented stratigraphic detail, surface to deep ocean variations and their relation to atmosphere and cryosphere changes through stadial-to-interstadial, glacial-to-interglacial and warmer than present time intervals.</p>

scholarly journals Orbital- and millennial-scale variability of the Antarctic Circumpolar Current over the past 140,000 years

2020 ◽  
Author(s):  
Shuzhuang Wu ◽  
Lester Lembke-Jene ◽  
Frank Lamy ◽  
Helge Arz ◽  
Norbert Nowaczyk ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ocean Circulation ◽  
Antarctic Circumpolar Current ◽  
Cold Water ◽  
Meridional Overturning Circulation ◽  
Global Ocean ◽  
The Past ◽  
Circumpolar Current ◽  
The Antarctic ◽  
Millennial Scale

Abstract The Antarctic Circumpolar Current (ACC) plays a crucial role in global ocean circulation by fostering deep-water upwelling and formation of new water masses. On geological time-scales, ACC variations are poorly constrained beyond the last glacial. Here, we reconstruct changes in ACC strength in the central Drake Passage over the past 140,000 years, based on grain-size and geochemical characteristics. We found significant glacial-interglacial changes of ACC flow speed, with reduced ACC intensity during glacials and a more vigorous circulation in interglacials. Superimposed on these orbital-scale changes are high-amplitude millennial-scale fluctuations, with ACC strength maxima correlating with diatom-based Antarctic winter sea-ice minima, particularly during full glacial conditions. We hypothesize that the ACC is closely linked to Southern Hemisphere millennial-scale climate oscillations, amplified through Antarctic sea ice extent changes. These strong ACC variations regulated Pacific-Atlantic water exchange via the “cold water route” and affected the Atlantic Meridional Overturning Circulation and marine carbon storage.

scholarly journals Interannual response of global ocean hindcasts to a satellite-based correction of precipitation fluxes

2012 ◽  
Vol 9 (2) ◽  
pp. 611-648 ◽  
Author(s):  
A. Storto ◽  
I. Russo ◽  
S. Masina
Keyword(s):  
Ocean Circulation ◽  
Surface Current ◽  
Global Ocean ◽  
Surface Salinity ◽  
Near Surface ◽  
Convergence Zones ◽  
Circumpolar Current ◽  
The Tropics ◽  
Spatially Varying ◽  
The Antarctic

Abstract. We present a methodology to correct precipitation fluxes from the ECMWF atmospheric reanalysis (ERA-Interim) for oceanographic applications. The correction is performed by means of a spatially varying monthly climatological coefficient, computed within the period 1989–2008 by comparison between ERA-Interim and a satellite-based passive microwave precipitation product. ERA-Interim exhibits a systematic over-estimation of precipitation within the inter-tropical convergence zones (up to 3 mm d−1) and under-estimation at mid- and high- latitudes (up to −4 mm d−1). The correction has been validated within eddy-permitting resolution global ocean hindcasts (1989–2009), demonstrating the ability of our strategy in attenuating the 20-yr mean global EMP negative imbalance by 16%, reducing the near-surface salinity fresh bias in the Tropics up to 1 psu and improving the representation of the sea level interannual variability, with an SSH error decrease of 8%. The ocean circulation is also proved to benefit from the correction, especially in correspondence of the Antarctic Circumpolar Current, where the error in the near-surface current speed decreases by a 9%. Finally, we show that the correction leads to volume and freshwater transports that better agree with independent estimates.

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.

Millennial-scale variability in Antarctic Circumpolar Current and its impacts during the last glacial cycle

2020 ◽  
Author(s):  
Shuzhuang Wu ◽  
Frank Lamy ◽  
Gerhard Kuhn ◽  
Lester Lembke-Jene ◽  
Xu Zhang ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Antarctic Circumpolar Current ◽  
Drake Passage ◽  
Global Ocean ◽  
Glacial Cycle ◽  
Last Glacial ◽  
Circumpolar Current ◽  
Global Ocean Circulation ◽  
The Last Glacial ◽  
Millennial Scale

<p>The Antarctic Circumpolar Current (ACC) is the largest current system in the world, linking the Pacific, Atlantic and Indian Ocean basins. However, the variability of the ACC, which plays a fundamental role on global ocean circulation and climate variability, is still poorly constrained. This information is crucial for understanding the role of the ACC on global ocean circulation in response to global warming. Here, we reconstruct changes in the ACC over the past 155,000 years based on sediment grain size variations recorded in a highly-resolved marine sedimentary record from the central Drake Passage near the Polar Front. Our results show significant changes in the ACC during the last glacial cycle and a remarkable boundary between the glacial and interglacial periods. Substantial decreases (~33% to ~47%) in the ACC flow speed from interglacial to glacial period, which corroborates and extends results of previous studies along the subantarctic northern limit of the ACC into the central Drake Passage. This strong variation of ACC likely plays a significant role in regulating Pacific-Atlantic water mass exchange via the “cold water route” and could significantly affect the Atlantic Meridional Overturning Circulation. Superimposed on these glacial-interglacial changes, we found strong millennial-scale variations in ACC current speed, increasing in amplitude close to full glacial conditions. We hypothesise that the central ACC increases its sensitivity to Southern Hemisphere millennial-scale climates oscillations, likely associated with westerlies’ wind stress and Antarctic sea ice extent once glacial conditions fully formed.</p>

Southern Ocean Response to Strengthening Winds in an Eddy-Permitting Global Climate Model

2010 ◽  
Vol 23 (19) ◽  
pp. 5332-5343 ◽  
Author(s):  
Paul Spence ◽  
John C. Fyfe ◽  
Alvaro Montenegro ◽  
Andrew J. Weaver
Keyword(s):  
Southern Ocean ◽  
Antarctic Circumpolar Current ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Temperature Response ◽  
Near Surface ◽  
Ocean Response ◽  
Circumpolar Current ◽  
The Antarctic

Abstract A global climate model with horizontal resolutions in the ocean ranging from relatively coarse to eddy permitting is used to investigate the resolution dependence of the Southern Ocean response to poleward intensifying winds through the past and present centuries. The higher-resolution simulations show poleward migration of distinct ocean fronts associated with a more highly localized near-surface temperature response than in the lower-resolution simulations. The higher-resolution simulations also show increasing southward eddy heat transport, less high-latitude cooling, and greater sea ice loss than the lower-resolution simulations. For all resolutions, from relatively coarse to eddy permitting, there is poleward migration of the Antarctic Circumpolar Current in the Atlantic and the western half of the Indian basin. Finally, zonal transports associated with the Antarctic Circumpolar Current are shown to be sensitive to resolution, and this is discussed in the context of recent observed change.

scholarly journals Southern Ocean overturning across streamlines in an eddying simulation of the Antarctic Circumpolar Current

Ocean Science ◽  
2007 ◽  
Vol 3 (4) ◽  
pp. 491-507 ◽  
Author(s):  
A. M. Treguier ◽  
M. H. England ◽  
S. R. Rintoul ◽  
G. Madec ◽  
J. Le Sommer ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Antarctic Circumpolar Current ◽  
Meridional Circulation ◽  
Dimensional Structure ◽  
Residual Circulation ◽  
Mean Flow ◽  
Buoyancy Forcing ◽  
Circumpolar Current ◽  
Surface Buoyancy ◽  
The Antarctic

Abstract. An eddying global model is used to study the characteristics of the Antarctic Circumpolar Current (ACC) in a streamline-following framework. Previous model-based estimates of the meridional circulation were calculated using zonal averages: this method leads to a counter-intuitive poleward circulation of the less dense waters, and underestimates the eddy effects. We show that on the contrary, the upper ocean circulation across streamlines agrees with the theoretical view: an equatorward mean flow partially cancelled by a poleward eddy mass flux. Two model simulations, in which the buoyancy forcing above the ACC changes from positive to negative, suggest that the relationship between the residual meridional circulation and the surface buoyancy flux is not as straightforward as assumed by the simplest theoretical models: the sign of the residual circulation cannot be inferred from the surface buoyancy forcing only. Among the other processes that likely play a part in setting the meridional circulation, our model results emphasize the complex three-dimensional structure of the ACC (probably not well accounted for in streamline-averaged, two-dimensional models) and the distinct role of temperature and salinity in the definition of the density field. Heat and salt transports by the time-mean flow are important even across time-mean streamlines. Heat and salt are balanced in the ACC, the model drift being small, but the nonlinearity of the equation of state cannot be ignored in the density balance.

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