Indo‐Atlantic Exchange, Mesoscale Dynamics, and Antarctic Intermediate Water

Capuano, Tonia Astrid; Speich, Sabrina; Carton, Xavier; Laxenaire, Rémi

doi:10.1002/2017jc013521

Cited by 8 publications

(8 citation statements)

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“…I‐AAIW lies in the easternmost sector of the section, east of 12°E in the Cape Basin and is characterized by oxygen concentrations lower than 200 μmol kg −1 . A third variety is sometimes called Indo‐Atlantic AAIW (IA‐AAIW, 34.2 < S P < 34.3; 34.4 < S A < 34.45), which is created by isopycnal mixing of A‐AAIW and I‐AAIW in the Cape Basin and covers a depth range of 800–1,000 m depth (Capuano et al., 2018; A. L. Gordon et al., 1987; Rusciano et al., 2012). Consequently IA‐AAIW is found between A‐AAIW and I‐AAIW, from the Mid‐Atlantic Ridge to ∼12°E (Figures 4c and 5b).…”

Section: Resultsmentioning

confidence: 99%

The South Atlantic Meridional Overturning Circulation and Mesoscale Eddies in the First GO‐SHIP Section at 34.5°S

et al. 2021

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The variability of the Atlantic meridional overturning circulation (AMOC) has considerable impacts on the global climate system. Past studies have shown that changes in the South Atlantic control the stability of the AMOC and drive an important part of its variability. That is why significant resources have been invested in a South (S)AMOC observing system. In January 2017, the RV Maria S. Merian conducted the first GO-SHIP hydrographic transect along the SAMOC-Basin Wide Array (SAMBA) line at 34.5°S in the South Atlantic. This paper presents estimates of meridional volume, freshwater (MFT), and heat (MHT) transports through the line using the slow varying geostrophic density field and direct velocity observations. An upper and an abyssal overturning cell are identified with a strength of 15.64 ± 1.39 Sv and 2.4 ± 1.6 Sv, respectively. The net northward MHT is 0.27 ± 0.10 PW, increasing by 0.12 PW when we remove the observed mesoscale eddies with a climatology derived from the Argo floats data set. We attribute this change to an anomalous predominance of cold core eddies during the cruise period. The highest velocities are observed in the western boundary, within the Brazil and the Deep Western Boundary currents. These currents appear as a continuous deep jet located 150 km off the slope squeezed between two cyclonic eddies. The zonal changes in water masses properties and velocity denote the imprint of exchange pathways with both the Southern and the Indian oceans. Plain Language Summary The Atlantic meridional overturning circulation (AMOC) is a crucial element of the global ocean circulation and climate. It connects the Southern Ocean to the northern North Atlantic, and is responsible for the interhemispheric northward transport of heat and freshwater. The South Atlantic is a crossroad for water masses from the Southern, the Indian and the North Atlantic oceans. This paper analyzes the first full-ocean-depth trans-basin measurements of the southernmost enclosed section of the Atlantic between South Africa and Brazil along 34.5°S. Our results confirm a northward transport of heat at this latitude. We also found a complex water mass structure and dynamics, characterized by intense boundary currents and mesoscale eddies. It is the sum of these elements that is not only crucial for the Atlantic but also for the global ocean circulation and climate. MANTA ET AL.

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Section: Resultsmentioning

confidence: 99%

The South Atlantic Meridional Overturning Circulation and Mesoscale Eddies in the First GO‐SHIP Section at 34.5°S

et al. 2021

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“…In the subtropical South Atlantic, it seems obvious that two regions dominate as venues of intense heat loss to the atmosphere. The western region is located at the confluence zone where the Brazil Current meets the Malvinas Current (Gordon, 1989), while the eastern region corresponds to the dynamics of Agulhas Rings in the southeastern Cape Basin, stimulated by the intrusion and retroflection of the Agulhas Current that brings warm and salty waters from the Indian Ocean (Capuano et al., 2018; Gordon et al., 1992; Speich et al., 2007). Those regions with intense cooling are also consistent with the EKE pattern shown in (d), suggesting a possible role of mesoscale dynamics in buoyancy loss, mode water formation, and transport.…”

Section: Resultsmentioning

confidence: 99%

Formation and Transport of the South Atlantic Subtropical Mode Water in Eddy‐Permitting Observations

2021

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The spatio-temporal variability of such heat and CO 2 uptake and storage is dependent on various physical mechanisms from both ocean surface and subsurface perspectives. Intuitively, air-sea heat and momentum fluxes generate and modulate sea surface temperature (SST) anomalies, which in turn, provide feedback to these fluxes (Park et al., 2005). In addition, studies have also observed and examined a reemergence mechanism of SST anomalies from one winter to another, without maintaining through the summer in between (Alexander & Deser, 1995;Deser et al., 2003;Hanawa & Sugimoto, 2004). Such reemergence has been linked to the presence of mode waters capped underneath the seasonal thermocline and characterized by a substantial volume of thermostad or pycnostad (a layer with low temperature or density gradients) distributed broadly in the ocean interior (Hanawa & Talley, 2001;Speer & Forget, 2013). The dynamical nature of mode waters is thus often

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“…Data from NAOS floats feed these research activities thanks to longer time series and improved sampling. Such research covers a broad range of topics including global sea-level variations (e.g., Cazenave et al, 2014;Dieng et al, 2017), ocean-heat and salt-content variations (e.g., Von Schuckmann et al, 2016), meridional circulation and deep convection (e.g., Piron et al, 2017), tropical dynamics (e.g., Cravatte et al, 2017), large-scale circulation (e.g., Sévellec et al, 2017), eddy dynamics (e.g., Capuano et al, 2018), satellite validation (e.g., Boutin et al, 2018), modeling and data assimilation (e.g., Turpin et al, 2016;Artana et al, 2018;Lellouche et al, 2018).…”

Section: Contribution To the Core Argo Programmentioning

confidence: 99%

Preparing the New Phase of Argo: Scientific Achievements of the NAOS Project

et al. 2020

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Argo, the international array of profiling floats, is a major component of the global ocean and climate observing system. In 2010, the NAOS (Novel Argo Observing System) project was selected as part of the French "Investissements d'Avenir" Equipex program. The objectives of NAOS were to consolidate the French contribution to Argo's core mission (global temperature and salinity measurements down to 2000 m), and also to develop the future generation of French Argo profiling floats and prepare the next phase of the Argo program with an extension to the deep ocean (Deep Argo), biogeochemistry (BGC-Argo) and polar seas. This paper summarizes how NAOS has met its objectives. The project significantly boosted France's contribution to Argo's core mission by deploying more than 100 NAOS standard Argo profiling floats. In addition, NAOS deployed new-generation floats as part of three scientific experiments: biogeochemical floats in the Mediterranean Sea, biogeochemical floats in the Arctic Ocean, and deep floats with oxygen sensors in the North Atlantic. The experiment in the Mediterranean Sea, launched in 2012, implemented and maintained a network of BGC-Argo floats at basin scale for the first time. The 32 BGC-Argo floats deployed and about 4000 BGC profiles collected have vastly improved characterization of the biogeochemical and ecosystem dynamics of the Mediterranean. Meanwhile, experiments in the Arctic and in the North Atlantic, starting in 2015 and deploying 20 Arctic BGC floats and 23 deep floats, have provided unique observations on biogeochemical cycles in the Arctic and deep-water masses, as well as ocean circulation variability in the North Atlantic. NAOS has therefore paved the way to the new operational phase of the Argo program in France that includes BGC and Deep Argo extensions. The objectives and characteristics of this new phase of Argo-France are discussed in the conclusion.

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Indo‐Atlantic Exchange, Mesoscale Dynamics, and Antarctic Intermediate Water

Cited by 8 publications

References 66 publications

The South Atlantic Meridional Overturning Circulation and Mesoscale Eddies in the First GO‐SHIP Section at 34.5°S

The South Atlantic Meridional Overturning Circulation and Mesoscale Eddies in the First GO‐SHIP Section at 34.5°S

Formation and Transport of the South Atlantic Subtropical Mode Water in Eddy‐Permitting Observations

Preparing the New Phase of Argo: Scientific Achievements of the NAOS Project

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