Bottom Currents Derived from a Shipborne ADCP on WOCE Cruise A11 in the South Atlantic

Saunders, Peter M.; King, Brian

doi:10.1175/1520-0485(1995)025<0329:bcdfas>2.0.co;2

Cited by 102 publications

(115 citation statements)

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“…Estimates of meridional trans-oceanic transports were compatible with values from the literature (Fu, 1981;Roemmich, 1983;Rintoul, 1991;Macdonald, 1993Macdonald, , 1998Matano and Philander, 1993;Holfort, 1994;Saunders and King, 1995;Barnier et al, 1996;Schlitzer, 1996;Speer et al, 1996;Holfort and Siedler, 2001;Sloyan and Rintoul, 2001a, b;Zhang et al, 2002;Vanicek and Siedler, 2002). Among the order of 300 OM calculations performed, the analysis based on the ARTICLE IN PRESS assumptions of a correlation length of 41 and a climatological error of 3 cm s À1 provide the best match between our results and those reported in the literature.…”

Section: Article In Presssupporting

confidence: 85%

Lagrangian circulation of Antarctic Intermediate Water in the subtropical South Atlantic

Núñez‐Riboni

Boebel

Ollitrault

et al. 2005

Deep Sea Research Part II: Topical Studies in Oceanography

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This study combines float data from different projects collected between 1991 and 2003 in the South Atlantic to describe the flow of Antarctic Intermediate Water (AAIW). Velocity space-time averages are calculated for various grid resolutions and with cells deformed to match the bathymetry, f/H or f/h (with H being the water depth and h being the thickness of the AAIW layer). When judged by the degree of alignment between respective isolines and the resulting average velocity fields, the best grid is based on a nominal cell size of 31 (latitude) by 41 (longitude) with cell shapes deformed according to f/h. Using this grid, objectively estimated mean currents (and their associated errors), as well as meridional and zonal volume transports are estimated. Results show an anticyclonic Subtropical Gyre centred near 361S and spanning from 23711S to 46711S. The South Atlantic Current meanders from 331S to 461S and shows a mean speed of 9.677.8 cm s À1 (8.573.5 Sv; 1 Sv ¼ 1 Â 10 6 m 3 s À1 ). The northern branch of the Subtropical Gyre is located between 221S and 321S and flows westward with a mean speed of 4.773.3 cm s À1 (9.373.4 Sv). Evidence of a cyclonic Tropical Gyre divided in two sub-cells is visible on the stream function. r

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Section: Article In Presssupporting

confidence: 85%

Lagrangian circulation of Antarctic Intermediate Water in the subtropical South Atlantic

Núñez‐Riboni

Boebel

Ollitrault

et al. 2005

Deep Sea Research Part II: Topical Studies in Oceanography

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“…The two horizontal velocity components, E-W (u, m s Ϫ1 ) and N-S (v, m s Ϫ1 ), were taken every 1.2 s in 8-m bins from the subsurface (16 m) down to 400 m. The calibration of the average velocities was done as recommended by Joyce (1989). The estimates were averaged to 5-min intervals and scanned for errors due to changes in ship position and speed (King and Cooper 1993;Saunders and King 1995).…”

Section: Methodsmentioning

confidence: 99%

Nitrate uptake and diffusive nitrate supply in the Central Atlantic

Planas

Agustı́

Duarte

et al. 1999

Limnology & Oceanography

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The latitudinal variation (35ЊS to 28ЊN) in the rate of diffusive nitrate supply across the thermocline and the associated variation in the uptake rate of nitrate and ammonium in the Central Atlantic was studied. The calculated diffusive nitrate flux showed a sharp latitudinal gradient, with the lowest nitrate supply (0.00037 mol m Ϫ3 d Ϫ1 ) in the South Atlantic subtropical gyre and the highest values (23.5 mol m Ϫ3 d Ϫ1 ) between the Equator and 15ЊN. The uptake rate of nitrate was inhibited at high irradiance at most stations. Both nitrate and ammonium uptake rates were lowest (about 3 and 10 mol m Ϫ3 d Ϫ1 , respectively) at the southern end of the transect and increased (about 20 and 55 mol m Ϫ3 d Ϫ1 , respectively) towards the Equator, with this increase being much greater for ammonium than for nitrate uptake. The f-ratio was highest (ഠ0.4) just south of the Equator and lowest (ഠ0.03) at the southern end of the transect. The slope between total uptake rate of dissolved inorganic nitrogen and gross primary production, calculated from O 2 -based measurements, in surface waters (4.72 Ϯ 1.54) was somewhat lower, but not significantly so, than the expected C/N ratio of 6.6. The average uptake rate of nitrate did not differ significantly from the average estimated diffusive supply of nitrate to the biogenic layer over the Central Atlantic. However, the nitrate uptake rate increased as the ⅓ power of the diffusive nitrate flux to the biogenic layer. As a result, nitrate uptake far exceeded (by up to 100-fold) the nitrate flux to the biogenic layer in the stations where the supply of nitrate was lowest. The excess nitrate uptake averaged 0.65 Ϯ 0.24 mmol NO 3 m Ϫ2 d Ϫ1 (range, 0.05-1.9 mmol NO 3 m Ϫ2 d Ϫ1 ), which must be supplied through atmospheric deposition and other perturbation events. This excess nitrate uptake is relatively large compared to the diffusive supply in the most unproductive areas, where external nitrate inputs fuel the new production. In contrast, these sources of nitrate are far less significant where high diffusive fluxes suffice to maintain high nitrate uptake rates.

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“…Rhines (1977) suggested the barotropic mode is dominant in the high energetic regions of the oceans such as the western boundary currents. Observational studies seem to corroborate this: the region near the Gulf Stream has been observed to bé mainly barotropic (Schmitz, 1980;Wunsch, 1997) as well as the Aghulas Current (Wunsch, 1997) and the Brazil and Malvinas Currents at the Confluence Zone (Peterson, 1992;Saunders and King, 1995).…”

mentioning

confidence: 81%

“…This distribution seems to be produced by barotropic instability according to Jayne et al (1993) Features on the mean circulation near the western boundary currents have also been observed, such as recirculation gyres of opposite sign to the north and south of the Gulf Stream (e.g. Hogg, 1983) and an anticyclonic cell in the Argentine Basin above a topographic feature known as the Zapiola Drift (Saunders and King, 1995).…”

mentioning

confidence: 87%

Mesoscale variability and mean flow interaction near the Gulf Stream as seen by satellite altimetry and numerical modelling

Botella¹

2001

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Bottom Currents Derived from a Shipborne ADCP on WOCE Cruise A11 in the South Atlantic

Cited by 102 publications

References 0 publications

Lagrangian circulation of Antarctic Intermediate Water in the subtropical South Atlantic

Lagrangian circulation of Antarctic Intermediate Water in the subtropical South Atlantic

Nitrate uptake and diffusive nitrate supply in the Central Atlantic

Mesoscale variability and mean flow interaction near the Gulf Stream as seen by satellite altimetry and numerical modelling

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