The Effect of Agulhas Eddies on Absorption and Transport of Anthropogenic Carbon in the South Atlantic Ocean

The South Atlantic Ocean is currently undergoing significant alterations due to climate change. This region is important to the global carbon cycle, but marine carbon data are scarce in this basin. Additionally, this region is influenced by Agulhas eddies. However, their effects on ocean biogeochemistry are not yet fully understood. Thus, we aimed to model the carbonate parameters in this region and investigate the anthropogenic carbon (Cant) content in 13 eddies shed by the Agulhas retroflection. We used in situ data from the CLIVAR/WOCE/A10 section to elaborate total dissolved inorganic carbon (CT) and total alkalinity (AT) models and reconstruct those parameters using in situ data from two other Brazilian initiatives. Furthermore, we applied the Tracer combining Oxygen, inorganic Carbon, and total Alkalinity (TrOCA) method to calculate the Cant, focusing on the 13 identified Agulhas eddies. The CT and AT models presented root mean square errors less than 1.66 and 2.19 μmol kg−1, indicating Global Ocean Acidification Observing Network climate precision. The Cant content in the Agulhas eddies was 23% higher than that at the same depths of the surrounding waters. We observed that Agulhas eddies can play a role in the faster acidification of the South Atlantic Central Water.

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The oceanic tides in the South Atlantic Ocean

Annales Geophysicae ◽

10.1007/s00585-994-0868-8 ◽

1994 ◽

Vol 12 (9) ◽

pp. 868-886 ◽

Cited By ~ 18

Author(s):

M. L. Genco ◽

F. Lyard ◽

C. Le Provost

Keyword(s):

Atlantic Ocean ◽

South Atlantic ◽

Weddell Sea ◽

South Atlantic Ocean ◽

Ocean Tide ◽

The South ◽

Patagonian Shelf ◽

In Situ Data ◽

Ocean Tide Model

Abstract. The finite element ocean tide model of Le Provost and Vincent (1986) has been applied to the simulation of the M2 and K1 components over the South Atlantic Ocean. The discretisation of the domain, of the order of 200 km over the deep ocean, is refined down to 15 km along the coasts, such refinement enables wave propagation and damping over the continental shelves to be correctly solved. The marine boundary conditions, from Dakar to Natal, through the Drake passage and from South Africa to Antarctica, are deduced from in situ data and from Schwiderski's solution and then optimised following a procedure previously developed by the authors. The solutions presented are in very good agreement with in situ data: the root mean square deviations from a standard subset of 13 pelagic stations are 1.4 cm for M2 and 0.45 cm for K1, which is significantly better overall than solutions published to date in the literature. Zooms of the M2 solution are presented for the Falkland Archipelago, the Weddell Sea and the Patagonian Shelf. The first zoom allows detailing of the tidal structure around the Falklands and its interpretation in terms of a stationary trapped Kelvin wave system. The second zoom, over the Weddell Sea, reveals for the first time what must be the tidal signal under the permanent ice shelf and gives a solution over that sea which is generally in agreement with observations. The third zoom is over the complex Patagonian Shelf. This zoom illustrates the ability of the model to simulate the tides, even over this area, with a surprising level of realism, following purely hydrodynamic modelling procedures, within a global ocean tide model. Maps of maximum associated tidal currents are also given, as a first illustration of a by-product of these simulations.

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First in situ record of the medusa stage of Cladonema radiatum (Cnidaria: Anthoathecata) in the South Atlantic Ocean

Ocean and Coastal Research ◽

10.1590/s2675-28242020068349 ◽

2020 ◽

Vol 68 ◽

Author(s):

Gabriel Bittencourt Farias ◽

Sigrid Neumann Leitão ◽

Pedro Augusto Mendes de Castro Melo ◽

Miodeli Nogueira Júnior ◽

Everton Giachini Tosetto

Keyword(s):

Atlantic Ocean ◽

South Atlantic ◽

South Atlantic Ocean ◽

The South ◽

Medusa Stage

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Derivation of seawater pCO2 from net community production identifies the South Atlantic Ocean as a CO2 source

10.5194/bg-2021-171 ◽

2021 ◽

Author(s):

Daniel Ford ◽

Gavin H. Tilstone ◽

Jamie D. Shutler ◽

Vassilis Kitidis

Keyword(s):

Atlantic Ocean ◽

Carbon Budget ◽

South Atlantic ◽

South Atlantic Ocean ◽

Global Ocean ◽

Biological Parameters ◽

The South ◽

Net Community Production ◽

Chl A ◽

Community Production

Abstract. A key step in assessing the global carbon budget is the determination of the partial pressure of CO2 in seawater (pCO2 (sw)). Spatially complete observational fields of pCO2 (sw) are routinely produced for regional and global ocean carbon budget assessments by extrapolating sparse in situ measurements of pCO2 (sw) using satellite observations. Within these schemes, satellite chlorophyll a (Chl a) is often used as a proxy for the biological drawdown or release of CO2. Chl a does not however quantify carbon fixed through photosynthesis and then respired, which is determined by net community production (NCP). In this study, pCO2 (sw) over the South Atlantic Ocean is estimated using a feed forward neural network (FNN) scheme and either satellite derived NCP, net primary production (NPP) or Chl a to compare which biological proxy is the most accurate. Estimates of pCO2 (sw) using NCP, NPP or Chl a were similar, but NCP was more accurate for the Amazon Plume and upwelling regions, which were not fully reproduced when using Chl a or NPP. Reducing the uncertainties in the satellite biological parameters to estimate pCO2 (sw), illustrated further improvement and greater differences for NCP compared to NPP or Chl a. Using NCP to estimate pCO2 (sw) showed that the South Atlantic Ocean is a CO2 source, whereas if no biological parameters are used in the FNN (following existing annual carbon assessments), this region becomes a sink for CO2. These results highlight that using NCP improved the accuracy of estimating pCO2 (sw), and changes the South Atlantic Ocean from a CO2 sink to a source. Reducing the uncertainties in NCP derived from satellite parameters will further improve our ability to quantify the global ocean CO2 sink.

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Derivation of seawater pCO2 from net community production identifies the South Atlantic Ocean as a CO2 source

Biogeosciences ◽

10.5194/bg-19-93-2022 ◽

2022 ◽

Vol 19 (1) ◽

pp. 93-115

Author(s):

Daniel J. Ford ◽

Gavin H. Tilstone ◽

Jamie D. Shutler ◽

Vassilis Kitidis

Keyword(s):

Atlantic Ocean ◽

Carbon Budget ◽

South Atlantic ◽

South Atlantic Ocean ◽

Global Ocean ◽

Biological Parameters ◽

The South ◽

Net Community Production ◽

Chl A ◽

Community Production

Abstract. A key step in assessing the global carbon budget is the determination of the partial pressure of CO2 in seawater (pCO2 (sw)). Spatially complete observational fields of pCO2 (sw) are routinely produced for regional and global ocean carbon budget assessments by extrapolating sparse in situ measurements of pCO2 (sw) using satellite observations. As part of this process, satellite chlorophyll a (Chl a) is often used as a proxy for the biological drawdown or release of CO2. Chl a does not, however, quantify carbon fixed through photosynthesis and then respired, which is determined by net community production (NCP). In this study, pCO2 (sw) over the South Atlantic Ocean is estimated using a feed forward neural network (FNN) scheme and either satellite-derived NCP, net primary production (NPP) or Chl a to compare which biological proxy produces the most accurate fields of pCO2 (sw). Estimates of pCO2 (sw) using NCP, NPP or Chl a were similar, but NCP was more accurate for the Amazon Plume and upwelling regions, which were not fully reproduced when using Chl a or NPP. A perturbation analysis assessed the potential maximum reduction in pCO2 (sw) uncertainties that could be achieved by reducing the uncertainties in the satellite biological parameters. This illustrated further improvement using NCP compared to NPP or Chl a. Using NCP to estimate pCO2 (sw) showed that the South Atlantic Ocean is a CO2 source, whereas if no biological parameters are used in the FNN (following existing annual carbon assessments), this region appears to be a sink for CO2. These results highlight that using NCP improved the accuracy of estimating pCO2 (sw) and changes the South Atlantic Ocean from a CO2 sink to a source. Reducing the uncertainties in NCP derived from satellite parameters will ultimately improve our understanding and confidence in quantification of the global ocean as a CO2 sink.

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