Observations of the Antarctic Slope Undercurrent in the southeastern Weddell Sea

Chavanne, Cédric; Heywood, Karen J.; Nicholls, Keith W.; Fer, Ilker

doi:10.1029/2010gl043603

Cited by 52 publications

(60 citation statements)

References 34 publications

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“…0. In this case the isotherms originating from the northern boundary would simply plunge into the continental slope, as observed in the Eastern Weddell Sea (Chavanne et al 2010) and other parts of the Antarctic margins where the continental shelf is narrow (Whitworth et al 1998). This configuration is illustrated in Fig.…”

Section: B Structure Of the Antarctic Slope Frontmentioning

confidence: 99%

“…This connects our theoretical understanding of the MOC in the ACC with that of the Antarctic Slope Front (ASF), a weaker westward current that flows along the continental slope around most of Antarctica (Jacobs 1991;Muench and Gordon 1995;Chavanne et al 2010). The ASF is driven by circumpolar easterly winds around the Antarctic margins (Large and Yeager 2009), and is characterized by steep ''V''-shaped isopycnals in AABW-forming regions of the continental shelf (Gill 1973;Thompson and Heywood 2008).…”

Section: Introductionmentioning

confidence: 99%

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Connecting Antarctic Cross-Slope Exchange with Southern Ocean Overturning

Stewart

Thompson

2013

Journal of Physical Oceanography

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Previous idealized investigations of Southern Ocean overturning have omitted its connection with the Antarctic continental shelves, leaving the influence of shelf processes on Antarctic Bottom Water (AABW) export unconsidered. In particular, the contribution of mesoscale eddies to setting the stratification and overturning circulation in the Antarctic Circumpolar Current (ACC) is well established, yet their role in cross-shelf exchange of water masses remains unclear. This study proposes a residual-mean theory that elucidates the connection between Antarctic cross-shelf exchange and overturning in the ACC, and the contribution of mesoscale eddies to the export of AABW. The authors motivate and verify this theory using an eddy-resolving process model of a sector of the Southern Ocean. The strength and pattern of the simulated overturning circulation strongly resemble those of the real ocean and are closely captured by the residualmean theory. Over the continental slope baroclinic instability is suppressed, and so transport by mesoscale eddies is reduced. This suppression of the eddy fluxes also gives rise to the steep ''V''-shaped isopycnals that characterize the Antarctic Slope Front in AABW-forming regions of the continental shelf. Furthermore, to produce water on the continental shelf that is dense enough to sink to the deep ocean, the deep overturning cell must be at least comparable in strength to wind-driven mean overturning on the continental slope. This results in a strong sensitivity of the deep overturning strength to changes in the polar easterly winds.

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Section: B Structure Of the Antarctic Slope Frontmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Connecting Antarctic Cross-Slope Exchange with Southern Ocean Overturning

Stewart

Thompson

2013

Journal of Physical Oceanography

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“…However, the constriction of the isopycnal surfaces creates a strong planetary potential vorticity (PV) gradient due to the shoreward increase of the stratification (see also Thompson et al 2014), which must be overcome to admit cross-slope CDW transport. This strong PV gradient appears to be accompanied by the formation of multiple along-slope jets, also visible in glider observations ) and in hydrographic surveys of the eastern Weddell Sea (Chavanne et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Eddy Generation and Jet Formation via Dense Water Outflows across the Antarctic Continental Slope

Stewart

Thompson

2016

Journal of Physical Oceanography

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Along various stretches of the Antarctic margins, dense Antarctic Bottom Water (AABW) escapes its formation sites and descends the continental slope. This export necessarily raises the isopycnals associated with lighter density classes over the continental slope, resulting in density surfaces that connect the near-freezing waters of the continental shelf to the much warmer circumpolar deep water (CDW) at middepth offshore. In this article, an eddy-resolving process model is used to explore the possibility that AABW export enhances shoreward heat transport by creating a pathway for CDW to access the continental shelf without doing any work against buoyancy forces. In the absence of a net alongshore pressure gradient, the shoreward CDW transport is effected entirely by mesoscale and submesoscale eddy transfer. Eddies are generated partly by instabilities at the pycnocline, sourcing their energy from the alongshore wind stress, but primarily by instabilities at the CDW-AABW interface, sourcing their energy from buoyancy loss on the continental shelf. This combination of processes induces a vertical convergence of eddy kinetic energy and alongshore momentum into the middepth CDW layer, sustaining a local maximum in the eddy kinetic energy over the slope and balancing the Coriolis force associated with the shoreward CDW transport. The resulting slope turbulence self-organizes into a series of alternating along-slope jets with strongly asymmetrical contributions to the slope energy and momentum budgets. Cross-shore variations in the potential vorticity gradient cause the jets to drift continuously offshore, suggesting that fronts observed in regions of AABW down-slope flow may in fact be transient features.

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“…The depth of the pycnocline, a key control on exchange across the shelf break, may be strongly dependent on the surface wind stress (Thoma et al, 2008;Spence et al, 2013;Jenkins et al, 2016, in this issue). In the eastern Weddell Sea upstream of the vast Filchner-Ronne Ice Shelf system, the pycnocline characteristically intersects the continental slope well below the shelf break, and the Antarctic Slope Undercurrent flows eastward on the slope (Chavanne et al, 2010). In the Amundsen Sea, in contrast, the pycnocline remains mostly above the level of the shelf break, especially where the shelf edge is cut by troughs (Jacobs et al, 2012).…”

mentioning

confidence: 97%