How well is the deep Tore seamount basin ventilated?

2020 ◽  
Author(s):  
Laura Antón ◽  
Susana Lebreiro ◽  
Silvia Nave ◽  
Luke Skinner ◽  
Elizabeth Michel ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Water Depth ◽  
Deep Water ◽  
Planktonic Foraminifera ◽  
Deep Ocean ◽  
South Atlantic ◽  
Age Difference ◽  
The South ◽  
Deep Basin ◽  
Iberian Margin

<p>The Last Glacial Maximum (LGM) was characterized by increased carbon storage in the deep ocean, as well as extremely poorly ventilated southern-sourced deep water (AABW) compared to northern-sourced deep water (NADW).</p><p>Here we analyse benthic (Cibicidoides wellerstorfi) d<sup>13</sup>C, and compare 3 sites sitting on the deep floor at 5 km water depth: MD13-3473 in the Tore inside basin; MD03-2698 in the Iberian margin; and TN057-21 in the South Atlantic. The Tore Seamount is a geological structure 300 km off the West Iberian margin at 40°N latitude. It has a crater-like morphology with a 5500 m deep basin in its middle, where calypso core MD13-3473 was collected, confined from the open ocean by a summit rim at 2200 m water depth (wd). The only connection between the deepest Tore Seamount basin and the Atlantic circulation is a NE gateway down to 4300 mwd.</p><p>The results for the LGM show similar values around -1.0 ‰ for the South Atlantic and the Iberian margin, in other words these sites were both bathed by AABW. However, the Tore basin record exhibits values around 0 ‰, similarly to open sites in the Iberian margin at 3.5 km depth. This seems to indicate a remarkable isolation of the Tore inside basin from the Atlantic deep bottom waters influence.</p><p>Among other things, we plan to examine the residence time of the Tore basin bottom water by measuring the radiocarbon age difference between benthic and planktonic foraminifera. </p><p>Our results confer to this enclosed environment the status of an in-situ deep ocean laboratory where to test hypotheses of past ocean circulation changes like the role of deep waters in sequestering glacial CO<sub>2</sub>. Core MD13-3473 covers 430 thousands of years, therefore 5 deglacial cycles (Spanish project “TORE5deglaciations”, CTM2017-84113-R, 2018-2020).</p>

New Deep Water Frontiers in the South Atlantic Equatorial Margins

2013 ◽  
Author(s):  
Marcio Rocha Mello ◽  
Tikae Takaki ◽  
Carlos Alberto Fontes ◽  
Webster Mohriak ◽  
Silvana Maria Barbanti ◽  
...  
Keyword(s):  
Deep Water ◽  
South Atlantic ◽  
The South

scholarly journals THE BIFURCATION OF THE WESTERN BOUNDARY CURRENT SYSTEM OF THE SOUTH ATLANTIC OCEAN

2014 ◽  
Vol 32 (2) ◽  
pp. 241 ◽  
Author(s):  
Janini Pereira ◽  
Mariela Gabioux ◽  
Martinho Marta Almeida ◽  
Mauro Cirano ◽  
Afonso M. Paiva ◽  
...  
Keyword(s):  
High Resolution ◽  
Atlantic Ocean ◽  
Ocean Circulation ◽  
South Atlantic ◽  
Western Boundary Current ◽  
South Atlantic Ocean ◽  
Western Boundary ◽  
Intermediate Water ◽  
Boundary Current ◽  
The South

ABSTRACT. The results of two high-resolution ocean global circulation models – OGCMs (Hybrid Coordinate Ocean Model – HYCOM and Ocean Circulation andClimate Advanced Modeling Project – OCCAM) are analyzed with a focus on the Western Boundary Current (WBC) system of the South Atlantic Ocean. The volumetransports are calculated for different isopycnal ranges, which represent the most important water masses present in this region. The latitude of bifurcation of the zonalflows reaching the coast, which leads to the formation of southward or northward WBC flow at different depths (or isopycnal levels) is evaluated. For the Tropical Water,bifurcation of the South Equatorial Current occurs at 13◦-15◦S, giving rise to the Brazil Current, for the South Atlantic Central Water this process occurs at 22◦S.For the Antarctic Intermediate Water, bifurcation occurs near 28◦-30◦S, giving rise to a baroclinic unstable WBC at lower latitudes with a very strong vertical shearat mid-depths. Both models give similar results that are also consistent with previous observational studies. Observations of the South Atlantic WBC system havepreviously been sparse, consequently these two independent simulations which are based on realistic high-resolution OGCMs, add confidence to the values presentedin the literature regarding flow bifurcations at the Brazilian coast.Keywords: Southwestern Atlantic circulation, water mass, OCCAM, HYCOM. RESUMO. Resultados de dois modelos globais de alta resolução (HYCOM e OCCAM) são analisados focando o sistema de Corrente de Contorno Oeste do Oceano Atlântico Sul. Os transportes de volume são calculados para diferentes níveis isopicnais que representam as principais massas de água da região. É apresentada a avaliação da latitude de bifurcação do fluxo zonal que atinge a costa, permitindo a formação dos fluxos da Corrente de Contorno Oeste para o sul e para o norte emdiferentes níveis de profundidades (ou isopicnal). Para a Água Tropical, a bifurcação da Corrente Sul Equatorial ocorre entre 13◦-15◦S, originando a Corrente do Brasil, e para a Água Central do Atlântico Sul ocorre em 22◦S. A bifurcação daÁgua Intermediária Antártica ocorre próximo de 28◦-30◦S, dando um aumento na instabilidade baroclínica da Corrente de Contorno Oeste em baixas latitudes e com um forte cisalhamento vertical em profundidades intermediárias. Ambos os modelos apresentamresultados similares e consistentes com estudos observacionais prévios. Considerando que as observações do sistema de Corrente de Contorno Oeste do Atlântico Sul são escassas, essas duas simulações independentes com modelos globais de alta resolução adicionam confiança aos valores apresentados na literatura, relacionadosaos fluxos das bifurcações na costa do Brasil.Palavras-chave: circulação do Atlântico Sudoeste, massas de água, OCCAM, HYCOM.

scholarly journals Glacial – interglacial atmospheric CO<sub>2</sub> change: a simple "hypsometric effect" on deep-ocean carbon sequestration?

2006 ◽  
Vol 2 (5) ◽  
pp. 711-743 ◽  
Author(s):  
L. C. Skinner
Keyword(s):  
Carbon Sequestration ◽  
Carbon Storage ◽  
Ocean Circulation ◽  
Deep Water ◽  
Deep Sea ◽  
Storage Capacity ◽  
Deep Ocean ◽  
Contributing Factors ◽  
Carbon Reservoir ◽  
Ocean Carbon

Abstract. Given the magnitude and dynamism of the deep marine carbon reservoir, it is almost certain that past glacial – interglacial fluctuations in atmospheric CO2 have relied at least in part on changes in the carbon storage capacity of the deep sea. To date, physical ocean circulation mechanisms that have been proposed as viable explanations for glacial – interglacial CO2 change have focussed almost exclusively on dynamical or kinetic processes. Here, a simple mechanism is proposed for increasing the carbon storage capacity of the deep sea that operates via changes in the volume of southern-sourced deep-water filling the ocean basins, as dictated by the hypsometry of the ocean floor. It is proposed that a water-mass that occupies more than the bottom 3 km of the ocean will essentially determine the carbon content of the marine reservoir. Hence by filling this interval with southern-sourced deep-water (enriched in dissolved CO2 due to its particular mode of formation) the amount of carbon sequestered in the deep sea may be greatly increased. A simple box-model is used to test this hypothesis, and to investigate its implications. It is suggested that up to 70% of the observed glacial – interglacial CO2 change might be explained by the replacement of northern-sourced deep-water below 2.5 km water depth by its southern counterpart. Most importantly, it is found that an increase in the volume of southern-sourced deep-water allows glacial CO2 levels to be simulated easily with only modest changes in Southern Ocean biological export or overturning. If incorporated into the list of contributing factors to marine carbon sequestration, this mechanism may help to significantly reduce the "deficit" of explained glacial – interglacial CO2 change.

scholarly journals First satellite tracks of South Atlantic sea turtle ‘lost years’: seasonal variation in trans-equatorial movement

2017 ◽  
Vol 284 (1868) ◽  
pp. 20171730 ◽  
Author(s):  
Katherine L. Mansfield ◽  
Milagros L. Mendilaharsu ◽  
Nathan F. Putman ◽  
Maria A. G. dei Marcovaldi ◽  
Alexander E. Sacco ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Environmental Changes ◽  
Circulation Model ◽  
Sea Turtle ◽  
South Atlantic ◽  
Swimming Velocity ◽  
The South ◽  
Frontal Zones ◽  
Few Data ◽  
Passive Drift

In the South Atlantic Ocean, few data exist regarding the dispersal of young oceanic sea turtles. We characterized the movements of laboratory-reared yearling loggerhead turtles from Brazilian rookeries using novel telemetry techniques, testing for differences in dispersal during different periods of the sea turtle hatching season that correspond to seasonal changes in ocean currents. Oceanographic drifters deployed alongside satellite-tagged turtles allowed us to explore the mechanisms of dispersal (passive drift or active swimming). Early in the hatching season turtles transited south with strong southward currents. Late in the hatching season, when currents flowed in the opposite direction, turtles uniformly moved northwards across the Equator. However, the movement of individuals differed from what was predicted by surface currents alone. Swimming velocity inferred from track data and an ocean circulation model strongly suggest that turtles' swimming plays a role in maintaining their position within frontal zones seaward of the continental shelf. The long nesting season of adults and behaviour of post-hatchlings exposes young turtles to seasonally varying ocean conditions that lead some individuals further into the South Atlantic and others into the Northern Hemisphere. Such migratory route diversity may ultimately buffer the population against environmental changes or anthropologic threats, fostering population resiliency.

scholarly journals On the intermediate and deep water flows in the South Atlantic Ocean

1997 ◽  
Vol 102 (C6) ◽  
pp. 12425-12440 ◽  
Author(s):  
Lionel Larqué ◽  
Keitapu Maamaatuaiahutapu ◽  
Véronique Garçon
Keyword(s):  
Atlantic Ocean ◽  
Deep Water ◽  
South Atlantic ◽  
South Atlantic Ocean ◽  
The South ◽  
Water Flows

OCEAN CIRCULATION MODES OF THE PHANEROZOIC: IMPLICATIONS FOR THE ANTIQUITY OF DEEP-SEA BENTHONIC INVERTEBRATES

Crustaceana ◽  
1999 ◽  
Vol 72 (8) ◽  
pp. 999-1018 ◽  
Author(s):  
David Horne
Keyword(s):  
Ocean Circulation ◽  
Deep Water ◽  
Thermohaline Circulation ◽  
Deep Ocean ◽  
Alternative View ◽  
Mass Extinctions ◽  
Anoxic Events ◽  
Deep Ocean Circulation ◽  
The Tropics ◽  
Time Of Origin

AbstractIt has been suggested that some modern anchialine cave invertebrates originated from deepsea ancestors of considerable antiquity (>100 million years). An alternative view is that such taxa could not have a long bathyal/abyssal history because of extended periods of anoxia in the oceans during the Mesozoic and Cainozoic, and that consequently their ancestors should be sought among shallow-water fauna. In order to assist in the evaluation of these opposing hypotheses, the Phanerozoic record of oxygen-deficient conditions in the water column is reviewed, with special regard for postulated ''anoxic events'' as a causative mechanism for major changes in biodiversity (e.g., mass extinctions). A key issue is the relative importance, through the Phanerozoic, of two types of deep ocean circulation: Halothermal Circulation (HTC), involving the formation of Warm Saline Deep Water (WSDW) in the tropics, promotes anoxia, while Thermohaline Circulation (THC), characterized by Cold Deep Water (CDW) formed at high latitudes, ventilates the deep ocean. Particular attention is paid to the evidence of the mid-Cretaceous Cenomanian-Turonian Boundary Event. The (apparently) widely accepted view that the deep ocean was mainly anoxic until about 40 million years ago (the time of origin of the modern psychrosphere) is challenged. Evidence from the deep-ocean record of bioturbated sediments suggests that there has been a Cold Deep Water component in ocean circulation for at least the last 90 million years (mid-Cretaceous onwards) and possibly throughout the Phanerozoic. This conclusion has important implications for hypotheses about the antiquity of deep-ocean benthonic invertebrate faunas. Es wurde vorgeschlagen, dass moderne, anchialine Hohleninvertebraten von Tiefseeformen bedeutenden Alters (>100 Millionen Jahre) abstammen. Eine alternative Ansicht besagt, dass solche Taxa aufgrund ausgedehnter, anoxischer Perioden im Mesozoikum und Kanozoikum keine besonders lange bathyale/abyssale Geschichte haben k onnen. Ihre Vorfahren solten daher bei Flachwasserformen gesucht werden. Um zur Evaluierung dieser gegensatzlichen Hypothesen beizutragen, werden Indizien fur sauerstoffarme Verhaltnisse in der Wassersaule wahrend des Phanerozoikums einer neuen Begutachtung unterzogen, mit bezonderer Berucksichtigung postulierter ''anoxischer Ereignisse'' als kausalem Mechanismus fur grossere Anderungen in der Biodiversitat (z. B. Massen-Aussterben). Ein Schlusselfaktor ist die relative Bedeutung zweier Typen von Tiefsee-Zirkulationen wahrend des Phanerozoikums. Die halothermale Zirkulation (Halothermal Curculation, HTC), die zur Bildung warmen, salinen Tiefenwassers (Warm Saline Deep Water, WSDW) in den Tropen fuhrt, fordert Anoxie, wahrend die thermohaline Zirkulation (Thermohaline Circulation, THC), charakterisiert durch in hohen Breiten gebildetes, kaltes Tiefenwasser (Cold Deep Water, CDW) die Tiefsee ventiliert. Besonderes Augenmerk wird auf die Ereignisse an der Cenoman-Turon-Grenze (Mittlere Kreide) gelegt. Die (offensichtlich) weithin akzeptierte Ansicht, dass die Tiefsee bis vor 40 Millionen Jahren grossteils anoxisch war (der Ursprungszeitpunkt der modernen Psychrosphare), wird in Frage gestellt. Hinweise auf durch Bioturbation gestorte TiefseeSedimente lassen vermuten, dass eine kalte Tiefenwasser-Komponente bei den Meereszirkulationen seit mindestens 90 Millionen Jahren (seit der mittleren Kreide), und moglicherweise wahrend des gesamten Phanerozoikums, existiert hat. Diese Schlussfolgerung hat wichtige Auswirkungen auf Hypothesen uber das Alter der benthischen Tiefsee-Evertebratenfauna.

Sign in / Sign up

Export Citation Format

Share Document