Brazil‐Malvinas Confluence: Water mass composition

Maamaatuaiahutapu, Keitapu; Garçon, Véronique; Provost, Christine; Boulahdid, Mostefa; Osiroff, Ana Paula

doi:10.1029/92jc00484

Cited by 56 publications

(38 citation statements)

References 15 publications

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“…is found at around 2500 m water depth and flows southward along the continental rise until it turns eastward at around 38° S (Maamaatuaiahutapu et al, 1992). Flow velocities in the NADW depth range are less than 5 cm s -1 (Hogg et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

Rapid lateral particle transport in the Argentine Basin: Molecular 14C and 230Thxs evidence

Mollenhauer

McManus

Benthien

et al. 2006

Deep Sea Research Part I: Oceanographic Research Papers

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Recent studies have revealed that lateral transport and focusing of particles strongly influences the depositional patterns of organic matter in marine sediments. Transport can occur in the water column prior to initial deposition or following sediment re-suspension. In both cases, fine-grained particles and organic-rich aggregates are more susceptible to lateral transport than coarse-grained particles (e.g. foraminiferal tests) because of the slower sinking velocities of the former. This may lead to spatial and, in the case of redistribution of resuspended sediments, temporal decoupling of organic matter from coarser sediment constituents. Prior studies from the Argentine Basin have yielded evidence that suspended particles are displaced significant distances (100 -1000 km) northward and downslope by strong surface and/or bottom currents. These transport processes result in anomalously cold alkenone-derived sea surface temperature (SST) estimates (up to 6°C colder than measured SST) and in the presence of frustules of Antarctic diatom species in surface sediments from Thxs-based focusing factors of 1.4 to 3.2 at sites where alkenone-based SST estimates were 4 -6 °C colder than measured values. In contrast, alkenone radiocarbon data suggest coeval deposition of marine biomarkers and planktic foraminifera, as alkenones in core-tops were younger than, or similar in age to, foraminifera. We therefore infer that the transport processes leading to the lateral displacement of these sediment components are rapid, and hence probably occur in the upper water column (< 1500 m).

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Section: Introductionmentioning

confidence: 99%

Rapid lateral particle transport in the Argentine Basin: Molecular 14C and 230Thxs evidence

Mollenhauer

McManus

Benthien

et al. 2006

Deep Sea Research Part I: Oceanographic Research Papers

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“…9°-3.6°C and 34.89-34.97 psu contributed from various sources such as Labrador Sea water, NorwegianGreenland Sea, and the Denmark Strait overflow waters (Talley and McCartney 1982;Swift 1984;Dickson and Brown 1994). As NADW is advected into the SA, its ϪS decreases to about 2°-3°C and 34.70-34.85 psu between 2000-and 3000-m depths at approximately 40°S in the southwestern Atlantic, due to mixing with colder and fresher CDW (e.g., Reid et al 1977;Maamaatuaiahutapu et al 1992;Tsuchiya et al 1994).…”

Section: Introductionmentioning

confidence: 99%

Circumpolar Deep Water Circulation and Variability in a Coupled Climate Model

Santoso

England

Hirst

2006

Journal of Physical Oceanography

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The natural variability of Circumpolar Deep Water (CDW) is analyzed using a long-term integration of a coupled climate model. The variability is decomposed using a standard EOF analysis into three separate modes accounting for 68% and 82% of the total variance in the upper and lower CDW layers, respectively. The first mode exhibits an interbasin-scale variability on multicentennial time scales, originating in the North Atlantic and flowing southward into the Southern Ocean via North Atlantic Deep Water (NADW). Salinity dipole anomalies appear to propagate around the Atlantic meridional overturning circulation on these time scales with the strengthening and weakening of NADW formation. The anomaly propagates northward from the midlatitude subsurface of the South Atlantic and sinks in the North Atlantic before flowing southward along the CDW isopycnal layers. This suggests an interhemispheric connection in the generation of the first CDW variability mode. The second mode shows a localized ϪS variability in the Brazil-Malvinas confluence zone on multidecadal to centennial time scales. Heat and salt budget analyses reveal that this variability is controlled by meridional advection driven by fluctuations in the strength of the Deep Western Boundary and the Malvinas Currents. The third mode suggests an Antarctic Intermediate Water source in the South Pacific contributing to variability in upper CDW. It is further found that NADW formation is mainly buoyancy driven on the time scales resolved, with only a weak connection with Southern Hemisphere winds. On the other hand, Southern Hemisphere winds have a more direct influence on the rate of NADW outflow into the Southern Ocean. The model's spatial pattern of ϪS variability is consistent with the limited observational record in the Southern Hemisphere. However, some observations of decadal CDW ϪS changes are beyond that seen in the model in its unperturbed state.

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“…The BC, the western boundary current associated with the subtropical gyre in the South Atlantic, turns southeast at -38øS [Olson et al, 1988], sheds warm rings with length scales of 400-500 km [Roden, 1986], and meanders back toward the north. Three water masses are found in the upper thousand meters in this region [Maamaatuaiahutapu et al, 1992]. The Thermocline Water, of subtropical origin and carried by the BC, is mostly confined to the continental break [Garfield, 1990].…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Brazil Current front variability from altimeter data

Goñi¹,

Wainer²

2001

J. Geophys. Res.

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Abstract. The southwestern Atlantic Ocean is characterized by the confluence of the Brazil and Malvinas Currents, which form very strong surface and subsurface fronts that can be detected from hydrographic and remote sensing observations. Three data sets, consisting of TOPEX/Poseidon-derived sea height anomalies, the climatologically derived depth of the 10øC isotherm, and reduced gravity, are used in conjunction with a two-layer dynamical ocean scheme to monitor the Brazil Current front and to investigate its variability during a 6 year period (1993)(1994)(1995)(1996)(1997)(1998). Results reveal that the fronts exhibit motions that are larger zonally than meridionally, showing strong interannual variability with annual mean amplitudes that range from 1 ø to 6 ø. The annual and semiannual components account for more than 75% of the variability of the frontal oscillations. In the annual cycle the frontal motions appear to be related closely to fluctuations in the baroclinic transport of the Brazil Current and are only influenced by the Malvinas Current when the Brazil Current transport is very small.

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Brazil‐Malvinas Confluence: Water mass composition

Cited by 56 publications

References 15 publications

Rapid lateral particle transport in the Argentine Basin: Molecular 14C and 230Thxs evidence

Rapid lateral particle transport in the Argentine Basin: Molecular 14C and 230Thxs evidence

Circumpolar Deep Water Circulation and Variability in a Coupled Climate Model

Investigation of the Brazil Current front variability from altimeter data

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