The Cape Cauldron: a regime of turbulent inter-ocean exchange

Boebel, Olaf; Lütjeharms, J. R. E.; Schmid, Claudia; Zenk, Walter; Rossby, T.; Barron, Charlie N.

doi:10.1016/s0967-0645(02)00379-x

Cited by 197 publications

(234 citation statements)

References 46 publications

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“…Some drifters and floats stopped looping near the ridge, and others changed looping characteristics indicating a disruption of the normal ring circulation by the ridge. The pattern of ring trajectories observed here matches rings tracked altimetrically by Byrne et al (1995), Goni et al (1997), Schouten et al (2000) and Boebel et al (2003).…”

Section: Anticyclones (Agulhas Rings)supporting

confidence: 87%

“…Acoustic float data in the region of interest have been previously discussed by Boebel et al (2003), Lutjeharms et al (2003), Richardson and Garzoli (2003), and Schmid et al (2003). This present work builds on those studies by combining all available acoustic float trajectories, nonacoustic float displacements, and surface drifter trajectories to further examine surface and subsurface velocity characteristics of the flow field of the southeastern Atlantic where Indian Ocean leakage begins its northward path toward the equator.…”

Section: Introductionmentioning

confidence: 84%

“…Overall objectives were to directly measure with floats the interocean exchange of water from the Agulhas into the South Atlantic and the advection of AAIW and its various mixing constituents in the South Atlantic. An important result was the observation of numerous cyclonic eddies in the Agulhas and in the southeastern Cape Basin Boebel et al, 2003). Some of them translated southwestward into the South Atlantic and appeared to trigger the pinching off of Agulhas rings .…”

Section: Scientific Backgroundmentioning

confidence: 99%

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Agulhas leakage into the Atlantic estimated with subsurface floats and surface drifters

Richardson

2007

Deep Sea Research Part I: Oceanographic Research Papers

158

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Section: Anticyclones (Agulhas Rings)supporting

confidence: 87%

Section: Introductionmentioning

confidence: 84%

Section: Scientific Backgroundmentioning

confidence: 99%

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Agulhas leakage into the Atlantic estimated with subsurface floats and surface drifters

Richardson

2007

Deep Sea Research Part I: Oceanographic Research Papers

158

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“…This observation supports the notion of the Cape Basin as a region of turbulent inter-ocean exchange (i.e. the Cape Cauldron, Boebel et al, 2003). There, eddy fluxes dominate both the closure of the Subtropical Gyre as well as the spicing up of fresh Atlantic AAIW with salty Indian Ocean AAIW (Lutjeharms, 1996).…”

Section: The Large-scale Circulationsupporting

confidence: 84%

Lagrangian circulation of Antarctic Intermediate Water in the subtropical South Atlantic

Núñez‐Riboni

Boebel

Ollitrault

et al. 2005

Deep Sea Research Part II: Topical Studies in Oceanography

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This study combines float data from different projects collected between 1991 and 2003 in the South Atlantic to describe the flow of Antarctic Intermediate Water (AAIW). Velocity space-time averages are calculated for various grid resolutions and with cells deformed to match the bathymetry, f/H or f/h (with H being the water depth and h being the thickness of the AAIW layer). When judged by the degree of alignment between respective isolines and the resulting average velocity fields, the best grid is based on a nominal cell size of 31 (latitude) by 41 (longitude) with cell shapes deformed according to f/h. Using this grid, objectively estimated mean currents (and their associated errors), as well as meridional and zonal volume transports are estimated. Results show an anticyclonic Subtropical Gyre centred near 361S and spanning from 23711S to 46711S. The South Atlantic Current meanders from 331S to 461S and shows a mean speed of 9.677.8 cm s À1 (8.573.5 Sv; 1 Sv ¼ 1 Â 10 6 m 3 s À1 ). The northern branch of the Subtropical Gyre is located between 221S and 321S and flows westward with a mean speed of 4.773.3 cm s À1 (9.373.4 Sv). Evidence of a cyclonic Tropical Gyre divided in two sub-cells is visible on the stream function. r

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“…Rings are shed on average every 2-3 months at a rate of 5-6 per year but there can be sustained periods with no rings produced (Schouten et al 2000). They are not easily measured, as turbulence in the Cape Basin leads to the decay of rings (Boebel et al 2003). As one ring is estimated to carry a volume transport of 0.5-1.5 Sv (Schouten et al 2000), with only 5-6 rings per year, rings cannot be the only vehicle of exchange as alone they cannot produce the estimated 15 Sv of transport reported by Richardson (2007).…”

Section: Introductionmentioning

confidence: 99%

Spatio-temporal characteristics of Agulhas leakage: a model inter-comparison study

et al. 2016

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west of the southern tip of Africa , is used to identify features that are robust regardless of the model used and takes into account the thermohaline biases of each model. When determined by a passive tracer method, 60 % of the magnitude of Agulhas leakage is captured and more than 80 % of its temporal fluctuations, suggesting that the method is appropriate for investigating the variability of Agulhas leakage. In all simulations but one, the major driver of variability is associated with mesoscale features passing through the section. High resolution (<1/10 • ) hindcast models agree on the temporal (2-4 cycles per year) and spatial (300-500 km) scales of these features corresponding to observed Agulhas Rings. Coarser resolution models (<1/4 • ) reproduce similar time scale of variability of Agulhas leakage in spite of their difficulties in representing the Agulhas rings properties. A coarser resolution climate model (2 • ) does not resolve the spatio-temporal mechanism of variability of Agulhas leakage. Hence it is expected to underestimate the contribution of Agulhas Current System to climate variability.

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The Cape Cauldron: a regime of turbulent inter-ocean exchange

Cited by 197 publications

References 46 publications

Agulhas leakage into the Atlantic estimated with subsurface floats and surface drifters

Agulhas leakage into the Atlantic estimated with subsurface floats and surface drifters

Lagrangian circulation of Antarctic Intermediate Water in the subtropical South Atlantic

Spatio-temporal characteristics of Agulhas leakage: a model inter-comparison study

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