scholarly journals Paleo Agulhas rings enter the subtropical gyre during the penultimate deglaciation

2013 ◽  
Vol 9 (6) ◽  
pp. 2631-2639 ◽  
Author(s):  
P. Scussolini ◽  
E. van Sebille ◽  
J. V. Durgadoo
Keyword(s):  
South Atlantic ◽  
The South ◽  
Data Set ◽  
The Core ◽  
Walvis Ridge ◽  
Core Site ◽  
Cape Basin ◽  
Globorotalia Truncatulinoides ◽  
Density Perturbations

Abstract. A maximum in the strength of Agulhas leakage has been registered at the interface between the Indian and South Atlantic oceans during glacial Termination II (T-II). This presumably transported the salt and heat necessary for maintaining the Atlantic circulation at rates similar to the present day. However, it was never shown whether these waters were effectively incorporated into the South Atlantic gyre, or whether they retroflected into the Indian and/or Southern oceans. To resolve this question, we investigate the presence of paleo Agulhas rings from a sediment core on the central Walvis Ridge, almost 1800 km farther into the Atlantic Basin than previously studied. Analysis of a 60 yr data set from the global-nested INALT01 model allows us to relate density perturbations at the depth of the thermocline to the passage of individual rings over the core site. Using this relation from the numerical model as the basis for a proxy, we generate a time series of variability of individual Globorotalia truncatulinoides δ18O. We reveal high levels of pycnocline depth variability at the site, suggesting enhanced numbers of Agulhas rings moving into the South Atlantic Gyre around T-II. Our record closely follows the published quantifications of Agulhas leakage from the east of the Cape Basin, and thus shows that Indian Ocean waters entered the South Atlantic circulation. This provides crucial support for the view of a prominent role of the Agulhas leakage in the shift from a glacial to an interglacial mode of the Atlantic circulation.

scholarly journals Paleo Agulhas rings enter the subtropical gyre during the penultimate deglaciation

2013 ◽  
Vol 9 (2) ◽  
pp. 2095-2114
Author(s):  
P. Scussolini ◽  
E. van Sebille
Keyword(s):  
Ocean Circulation ◽  
Circulation Model ◽  
South Atlantic ◽  
Meridional Overturning Circulation ◽  
Global Ocean ◽  
The South ◽  
Cape Basin ◽  
Globorotalia Truncatulinoides ◽  
Density Perturbations ◽  
Global Ocean Circulation

Abstract. A maximum in the strength of Agulhas Leakage has been registered at the interface between Indian and South Atlantic oceans during glacial Termination II (T II), presumably transporting the salt and heat necessary to maintain the Atlantic Meridional Overturning Circulation (AMOC) at rates similar to the present day. However, it was never shown whether these were effectively incorporated in the South Atlantic gyre, or whether they retroflected into the Indian and/or Southern Oceans. To solve this question, we investigate the presence of paleo Agulhas rings from a sediment core on the central Walvis Ridge, almost 1800 km farther into the Atlantic basin than previously studied. Analysis of a 20 yr dataset from a global ocean circulation model allows us to relate density perturbations, at the depth of the thermocline, to the passage of individual rings over the core site. Using this relation from the numerical model as the basis for a proxy, we generate a time series of δ18O variability of Globorotalia truncatulinoides single specimens, revealing high levels of pycnocline depth variability at the site, suggesting enhanced numbers of Agulhas rings moving into the South Atlantic gyre around and before T II. Our record closely follows the published quantifications of Agulhas Leakage from the east of the Cape Basin, and thus shows that Indian Ocean waters entered the South Atlantic circulation. This provides crucial support to the view of a prominent role of the Agulhas Leakage in the shift from a glacial to an interglacial mode of AMOC.

scholarly journals Characteristics and robustness of Agulhas leakage estimates: an inter-comparison study of Lagrangian methods

Ocean Science ◽  
2021 ◽  
Vol 17 (4) ◽  
pp. 1067-1080
Author(s):  
Christina Schmidt ◽  
Franziska U. Schwarzkopf ◽  
Siren Rühs ◽  
Arne Biastoch
Keyword(s):  
Global Climate ◽  
Horizontal Resolution ◽  
South Atlantic ◽  
Comparison Study ◽  
The South ◽  
Agulhas Current ◽  
Cape Basin ◽  
Total Transport ◽  
The Indian Ocean ◽  
Ice Model

Abstract. The inflow of relatively warm and salty water from the Indian Ocean into the South Atlantic via Agulhas leakage is important for the global overturning circulation and the global climate. In this study, we analyse the robustness of Agulhas leakage estimates as well as the thermohaline property modifications of Agulhas leakage south of Africa. Lagrangian experiments with both the newly developed tool Parcels and the well established tool Ariane were performed to simulate Agulhas leakage in the eddy-rich ocean–sea-ice model INALT20 (1/20∘ horizontal resolution) forced by the JRA55-do atmospheric boundary conditions. The average transport, its variability, trend and the transit time from the Agulhas Current to the Cape Basin of Agulhas leakage is simulated comparably with both Lagrangian tools, emphasizing the robustness of our method. Different designs of the Lagrangian experiment alter in particular the total transport of Agulhas leakage by up to 2 Sv, but the variability and trend of the transport are similar across these estimates. During the transit from the Agulhas Current at 32∘ S to the Cape Basin, a cooling and freshening of Agulhas leakage waters occurs especially at the location of the Agulhas Retroflection, resulting in a density increase as the thermal effect dominates. Beyond the strong air–sea exchange around South Africa, Agulhas leakage warms and salinifies the water masses below the thermocline in the South Atlantic.

Dual role of DOM in a scenario of global change on photosynthesis and structure of coastal phytoplankton from the South Atlantic Ocean

2018 ◽  
Vol 634 ◽  
pp. 1352-1361 ◽  
Author(s):  
Virginia E. Villafañe ◽  
Joanna Paczkowska ◽  
Agneta Andersson ◽  
Cristina Durán Romero ◽  
Macarena S. Valiñas ◽  
...  
Keyword(s):  
Global Change ◽  
Atlantic Ocean ◽  
South Atlantic ◽  
Dual Role ◽  
South Atlantic Ocean ◽  
The South ◽  
Coastal Phytoplankton

scholarly journals Stalked crinoids (Echinodermata) collected by the R/V Polarstern and Meteor in the south Atlantic and in Antarctica

Zootaxa ◽  
2012 ◽  
Vol 3425 (1) ◽  
pp. 1 ◽  
Author(s):  
MARC ELÉAUME ◽  
JENS-MICHAEL BOHN ◽  
MICHEL ROUX ◽  
NADIA AMÉZIANE
Keyword(s):  
North Atlantic ◽  
Deep Sea ◽  
South Atlantic ◽  
The South ◽  
The West ◽  
Walvis Ridge ◽  
The North ◽  
West Antarctic ◽  
Stalked Crinoids ◽  
Hard Substrates

During the last decades, R/V Meteor and R/V Polarstern deep-sea investigations in the south Atlantic and neighbouringSouthern Ocean collected new samples of stalked crinoids belonging to the families Bathycrinidae, Phrynocrinidae andHyocrinidae which are herein described. The species found are Bathycrinus australis A.H. Clark, 1907b (the most abun-dant), Dumetocrinus aff. antarcticus (Bather, 1908), Hyocrinus bethellianus Thomson, 1876, Feracrinus heinzelleri newspecies, and Porphyrocrinus cf. incrassatus (Gislén, 1933). As only stalk fragments of bathycrinids were frequently col-lected, a distinction between the two Atlantic species B. australis and B. aldrichianus is proposed using characters of co-lumnal articulations. A few specimens attributed to Porphyrocrinus cf. incrassatus, Hyocrinus bethellianus and Hyocrinussp. collected by the N/O Jean Charcot on the Walvis Ridge are also described, plus a new specimen of Porphyrocrinusincrassatus collected in the central mid-Atlantic. Biogeography and close affinities between species in the genera Bathy-crinus and Porphyrocrinus suggest an Antarctic origin of some stalked crinoids among the north Atlantic deep-sea fauna.The presence of B. australis in both the Angola and Cape basins suggests that the Walvis Ridge is not a bio-geographicalbarrier for this relatively eurybathic species, which can attach to hard substrates as well as anchor in sediment. The genusDumetocrinus seems to be an example of colonization of the west Antarctic platform from deeper environment where its ancestor lived.

New species of Neotanais Beddard, 1886 (Crustacea, Tanaidacea) from the deep sea of the tropical and southern East Atlantic Ocean

Zootaxa ◽  
2009 ◽  
Vol 1992 (1) ◽  
pp. 20-36 ◽  
Author(s):  
SIMON WEIGMANN ◽  
JÜRGEN GUERRERO-KOMMRITZ
Keyword(s):  
New Species ◽  
Atlantic Ocean ◽  
Deep Sea ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
Full Description ◽  
The South ◽  
East Atlantic ◽  
Cape Basin

As part of the sampling efforts during the DIVA-II expedition several Tanaidacea of the genus Neotanais were captured in the Guinea and the Cape Basin in the tropical and southern East Atlantic Ocean. Two different species were sampled, Neotanais rotermundiae sp. n. from the Guinea and Neotanais guskei sp. n. from the Cape Basin. The distribution of both species is limited to these basins. A full description for both species is presented. Neotanais guskei sp. n. is the largest Neotanais reported for the South Atlantic Ocean.

scholarly journals The Role of Interocean Exchanges on Decadal Variations of the Meridional Heat Transport in the South Atlantic

2011 ◽  
Vol 41 (8) ◽  
pp. 1498-1511 ◽  
Author(s):  
Shenfu Dong ◽  
Silvia Garzoli ◽  
Molly Baringer
Keyword(s):  
Indian Ocean ◽  
Heat Transport ◽  
South Atlantic ◽  
Similar Response ◽  
The South ◽  
Meridional Heat Transport ◽  
Interior Region ◽  
The Pacific ◽  
The Indian Ocean

Abstract The interocean exchange of water from the South Atlantic with the Pacific and Indian Oceans is examined using the output from the ocean general circulation model for the Earth Simulator (OFES) during the period 1980–2006. The main objective of this paper is to investigate the role of the interocean exchanges in the variability of the Atlantic meridional overturning circulation (AMOC) and its associated meridional heat transport (MHT) in the South Atlantic. The meridional heat transport from OFES shows a similar response to AMOC variations to that derived from observations: a 1 Sv (1 Sv ≡ 106 m3 s−1) increase in the AMOC strength would cause a 0.054 ± 0.003 PW increase in MHT at approximately 34°S. The main feature in the AMOC and MHT across 34°S is their increasing trends during the period 1980–93. Separating the transports into boundary currents and ocean interior regions indicates that the increase in transport comes from the ocean interior region, suggesting that it is important to monitor the ocean interior region to capture changes in the AMOC and MHT on decadal to longer time scales. The linear increase in the MHT from 1980 to 1993 is due to the increase in advective heat converged into the South Atlantic from the Pacific and Indian Oceans. Of the total increase in the heat convergence, about two-thirds is contributed by the Indian Ocean through the Agulhas Current system, suggesting that the warm-water route from the Indian Ocean plays a more important role in the northward-flowing water in the upper branch of the AMOC at 34°S during the study period.

scholarly journals Variability of carbon monoxide and carbon dioxide apparent quantum yield spectra in three coastal estuaries of the South Atlantic Bight

2012 ◽  
Vol 9 (6) ◽  
pp. 6947-6985 ◽  
Author(s):  
H. E. Reader ◽  
W. L. Miller
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Quantum Yield ◽  
South Atlantic ◽  
South Atlantic Bight ◽  
The South ◽  
Apparent Quantum Yield ◽  
Data Set ◽  
Direct Production ◽  
Coastal System

Abstract. The photochemical oxidation of oceanic dissolved organic carbon (DOC) to carbon monoxide (CO) and carbon dioxide (CO2) has been estimated to be a significant process with global photoproduction transforming petagrams of DOC to inorganic carbon annually. To further quantify the importance of these two photoproducts in coastal DOC cycling, 38 paired apparent quantum yield (AQY) spectra for CO and CO2 were determined at three locations along the coast of Georgia, USA over the course of one year. The AQY spectra for CO2 were considerably more varied than CO. CO AQY spectra exhibited a seasonal shift in spectrally integrated (260 nm–490 nm) AQY from higher efficiencies in the fall to less efficient photoproduction in the summer. While full-spectrum photoproduction rates for both products showed positive correlation with pre-irradiation UV-B sample absorption (i.e. chromophoric dissolved organic matter, CDOM) as expected, we found no correlation between AQY and CDOM for either product at any site. Molecular size, approximated with pre-irradiation spectral slope coefficients, and aromatic content, approximated by the specific ultraviolet absorption of the pre-irradiated samples, were also not correlated with AQY in either data set. The ratios of CO2 to CO photoproduction determined using both an AQY model and direct production comparisons were 23.2 ± 12.5 and 22.5 ± 9.0, respectively. Combined, both products represent a loss of 2.2 to 2.6 % of the DOC delivered to the estuaries and inner shelf of the South Atlantic Bight yearly, and 5 to 6 % of the total annual degassing of CO2 to the atmosphere. This result suggests that direct photochemical production of CO and CO2 is a small, yet significant contributor to both DOC cycling and CO2 gas exchange in this coastal system.

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