Tasman Leakage of intermediate waters as inferred from Argo floats

Fieschi, Miquel Rosell; Rintoul, Stephen R.; Gourrion, Jérôme; Pelegrí, Josep Lluís

doi:10.1002/2013gl057797

Cited by 21 publications

(12 citation statements)

References 27 publications

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“…For TL, a large portion of the 10.6 Sv comes from recirculations across the initial section [ Sallée et al ., ]. The portion originating from between Tasmania and 50°S as Tasman leakage (3.1 Sv) commensurate previous findings [ van Sebille et al ., ; Rosell‐Fieschi et al ., ].…”

Section: Resultsmentioning

confidence: 99%

“…Derived from observational subsurface autonomous floats, Rosell‐Fieschi et al . [] reported a westward transport of 5.2 ± 1.8 Sv at 115°E at intermediate depth. Despite the fact that both interocean exchanges north and south of Australia being of Pacific origin could arguably be related to large scale wind patterns [e.g., Feng et al ., ], van Sebille et al .…”

Section: Introductionmentioning

confidence: 99%

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Indian Ocean sources of Agulhas leakage

et al. 2017

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We examine the mean pathways, transit timescales, and transformation of waters flowing from the Pacific and the marginal seas through the Indian Ocean (IO) on their way toward the South Atlantic within a high‐resolution ocean/sea‐ice model. The model fields are analyzed from a Lagrangian perspective where water volumes are tracked as they enter the IO. The IO contributes 12.6 Sv to Agulhas leakage, which within the model is 14.1 ± 2.2 Sv, the rest originates from the South Atlantic. The Indonesian Through‐flow constitutes about half of the IO contribution, is surface bound, cools and salinificates as it leaves the basin within 10–30 years. Waters entering the IO south of Australia are at intermediate depths and maintain their temperature‐salinity properties as they exit the basin within 15–35 years. Of these waters, the contribution from Tasman leakage is 1.4 Sv. The rest stem from recirculation from the frontal regions of the Southern Ocean. The marginal seas export 1.0 Sv into the Atlantic within 15–40 years, and the waters cool and freshen on‐route. However, the model's simulation of waters from the Gulfs of Aden and Oman are too light and hence overly influenced by upper ocean circulations. In the Cape Basin, Agulhas leakage is well mixed. On‐route, temperature‐salinity transformations occur predominantly in the Arabian Sea and within the greater Agulhas Current region. Overall, the IO exports at least 7.9 Sv from the Pacific to the Atlantic, thereby quantifying the strength of the upper cell of the global conveyor belt.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Indian Ocean sources of Agulhas leakage

et al. 2017

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“…The largest core is found in the upper 300 m and a smaller core is found between 600 and 1200 m. These cores are consistent with the separation of the Indonesian surface water from the deeper Indonesian Intermediate water as found by Talley and Sprintall []. In the eastern Indian Ocean, the Tasman leakage flow is mainly confined south of 15°S, and between 300 and 1100 m. This deep Tasman leakage pathway carrying intermediate water has recently been confirmed in Argo data [ Rosell‐Fieschi et al ., ].…”

Section: Resultsmentioning

confidence: 99%

Pacific‐to‐Indian Ocean connectivity: Tasman leakage, Indonesian Throughflow, and the role of ENSO

et al. 2014

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The upper ocean circulation of the Pacific and Indian Oceans is connected through both the Indonesian Throughflow north of Australia and the Tasman leakage around its south. The relative importance of these two pathways is examined using virtual Lagrangian particles in a high-resolution nested ocean model. The unprecedented combination of a long integration time within an eddy-permitting ocean model simulation allows the first assessment of the interannual variability of these pathways in a realistic setting. The mean Indonesian Throughflow, as diagnosed by the particles, is 14.3 Sv, considerably higher than the diagnosed average Tasman leakage of 4.2 Sv. The time series of Indonesian Throughflow agrees well with the Eulerian transport through the major Indonesian Passages, validating the Lagrangian approach using transport-tagged particles. While the Indonesian Throughflow is mainly associated with upper ocean pathways, the Tasman leakage is concentrated in the 400-900 m depth range at subtropical latitudes. Over the effective period considered , no apparent relationship is found between the Tasman leakage and Indonesian Throughflow. However, the Indonesian Throughflow transport correlates with ENSO. During strong La Niñas, more water of Southern Hemisphere origin flows through Makassar, Moluccas, Ombai, and Timor Straits, but less through Moluccas Strait. In general, each strait responds differently to ENSO, highlighting the complex nature of the ENSO-ITF interaction.

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“…CFCs show this influx of mode and intermediate waters joining the Indian Ocean subtropical gyre around 60°E (Fine, ). The Indonesian Throughflow is estimated to be 15 Sv on average (Sprintall et al, ), the Tasman leakage another net 4 Sv (Rosell‐Fieschi et al, ; Speich et al, ), and the contribution from the Southern Ocean, which is probably the least constrained, perhaps 1–2 Sv or as much as 5 Sv (Durgadoo et al, ; Friocourt et al, ). These influxes must be balanced by an outflux, requiring an Agulhas leakage of at least 20 Sv.…”

Section: Discussionmentioning

confidence: 99%

A New Improved Estimation of Agulhas Leakage Using Observations and Simulations of Lagrangian Floats and Drifters

2020

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A new estimate of Agulhas leakage transport is calculated using profiling floats and drifters.Since Richardson's seminal estimate of 15 Sv in 2007, the number of floats and drifters passing through the Agulhas Current has quadrupled. Within uncertainties we find the same leakage percentages as Richardson, with 34% of drifters leaking at the surface and 21% of floats leaking at 1,000 m depth. We find that the drifters tend to follow a northward leakage pathway via the Benguela Current compared to the northwestward leakage pathway of the floats along the Agulhas Ring corridor. We simulate the isobaric and profiling behavior of the floats and drifters using two high resolution models and two offline Lagrangian tracking tools, quantifying for the first time the sampling biases associated with the observations. We find that the isobaric bias cannot be robustly simulated but likely causes an underestimate of observed leakage by one or two Sverdrups. The profiling behavior of the floats causes no significant bias in the leakage. Fitting a simulated vertical leakage profile to the observed leakage percentages from the floats and drifters and using the mean Agulhas transport observed by a moored array at 34 • S we find an improved Agulhas leakage transport of 21.3 Sv, with an estimated error of 4.7 Sv. Our new leakage transport is higher primarily because we account for leakage at depths down to 2,000 m, while Richardson considered only the top 1,000 m of the water column. Plain Language SummaryWe calculate a new estimation of Agulhas leakage using floats and drifters. Since most recent estimate of 15 Sv was calculated in 2007, we have had four times as many observations pass through the Agulhas Current. We find more drifters leak at the surface than floats at intermediate depth. The drifters follow a northward leakage passage compared to the northwestward passage of the floats. Using two models and two particle tracking tools, we mimic the behavior of these floats and drifters to better understand and quantify the sampling biases associated with these observations. Combining the results from the observations and these simulations, we calculate a new improved leakage transport of 21.3 Sv with an error of 4.7 Sv.Quantifying Agulhas leakage is difficult, with previous estimates ranging from 2 to 20 Sv (1 Sv = 1 × 10 6 m 3 s −1 ). The Cape Basin features the highest eddy kinetic energy outside a western boundary current system in the world (Chelton et al., 2011). Due to this highly turbulent nature, the mixing and stirring

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Tasman Leakage of intermediate waters as inferred from Argo floats

Cited by 21 publications

References 27 publications

Indian Ocean sources of Agulhas leakage

Indian Ocean sources of Agulhas leakage

Pacific‐to‐Indian Ocean connectivity: Tasman leakage, Indonesian Throughflow, and the role of ENSO

A New Improved Estimation of Agulhas Leakage Using Observations and Simulations of Lagrangian Floats and Drifters

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