scholarly journals The influence of the Brazil and Malvinas Currents on the southwestern Atlantic shelf circulation

2010 ◽  
Vol 7 (2) ◽  
pp. 837-871 ◽  
Author(s):  
R. P. Matano ◽  
E. D. Palma ◽  
A. R. Piola
Keyword(s):  
World Ocean ◽  
Deep Ocean ◽  
Western Boundary ◽  
Oceanic Circulation ◽  
Southwestern Atlantic ◽  
The South ◽  
Wind Speeds ◽  
The North ◽  
Brazil Current ◽  
South Brazil

Abstract. The oceanic circulation over the southwestern Atlantic shelf is influenced by large tidal amplitudes, substantial freshwater discharges, high wind speeds and – most importantly – by its proximity to two of the largest western boundary currents of the world ocean: the Brazil and Malvinas currents. This review article aims to describe the dynamical processes controlling the interaction between the shelf and the deep-ocean. The discussion is focused on two broad regions: the South Brazil Bight to the north, and Patagonia to the south. The exchanges between the Brazil Current and the South Brazil Bight are characterized by the intermittent development of eddies and meanders of the Brazil Current at the shelfbreak. However, it is argued that this is not the only – nor the most important – influence of the Brazil Current on the shelf. Numerical simulations show that the thermohaline structure of the South Brazil Bight can be entirely ascribed to steady state, bottom boundary layer interactions between the shelf and the Brazil Current. The Malvinas Current does not show the development of eddies and meanders, but its influence on the Patagonian shelf is no less important. Models and observations indicate that the Malvinas Current not only controls the shelfbreak dynamics and cross-shelf exchanges but also the circulation in the shelf's interior.

scholarly journals The influence of the Brazil and Malvinas Currents on the Southwestern Atlantic Shelf circulation

Ocean Science ◽  
2010 ◽  
Vol 6 (4) ◽  
pp. 983-995 ◽  
Author(s):  
R. P. Matano ◽  
E. D. Palma ◽  
A. R. Piola
Keyword(s):  
World Ocean ◽  
Deep Ocean ◽  
Western Boundary ◽  
Oceanic Circulation ◽  
Southwestern Atlantic ◽  
The South ◽  
Wind Speeds ◽  
The North ◽  
Brazil Current ◽  
South Brazil

Abstract. The oceanic circulation over the southwestern Atlantic shelf is influenced by large tidal amplitudes, substantial freshwater discharges, high wind speeds and – most importantly – by its proximity to two of the largest western boundary currents of the world ocean: the Brazil and Malvinas currents. This review article aims to discriminate the dynamical processes controlling the interaction between this extensive shelf region and the deep-ocean. The discussion is focused on two broad regions: the South Brazil Bight to the north, and Patagonia to the south. The exchanges between the Brazil Current and the South Brazil Bight are characterized by the intermittent development of eddies and meanders of the Brazil Current at the shelfbreak. However, it is argued that this is not the only – nor the most important – influence of the Brazil Current on the shelf. Numerical simulations show that the thermohaline structure of the South Brazil Bight can be entirely ascribed to steady state, bottom boundary layer interactions between the shelf and the Brazil Current. The Malvinas Current does not show the development of eddies and meanders, but its influence on the Patagonian shelf is not less important. Models and observations indicate that the Malvinas Current not only controls the shelfbreak dynamics and cross-shelf exchanges but also influences the circulation in the shelf's interior.

scholarly journals Control of oceanic circulation on sediment distribution in the southwestern Atlantic margin (23 to 55° S)

Ocean Science ◽  
2021 ◽  
Vol 17 (5) ◽  
pp. 1213-1229
Author(s):  
Michel Michaelovitch de Mahiques ◽  
Roberto Violante ◽  
Paula Franco-Fraguas ◽  
Leticia Burone ◽  
Cesar Barbedo Rocha ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Intermediate Water ◽  
Oceanic Circulation ◽  
Southwestern Atlantic ◽  
Sediment Distribution ◽  
Isotopic Signatures ◽  
The North ◽  
Brazil Current ◽  
Lower Circumpolar Deep Water ◽  
Atlantic Margin

Abstract. In this study, we interpret the role played by ocean circulation in sediment distribution on the southwestern Atlantic margin using radiogenic Nd and Pb isotopes. The latitudinal trends for Pb and Nd isotopes reflect the different current systems acting on the margin. The utilization of the sediment fingerprinting method allowed us to associate the isotopic signatures with the main oceanographic features in the area. We recognized differences between Nd and Pb sources to the Argentinean shelf (carried by the flow of Subantarctic Shelf Water) and slopes (transported by deeper flows). Sediments from Antarctica extend up to the Uruguayan margin, carried by the Upper and Lower Circumpolar Deep Water. Our data confirm that, for shelf and intermediate areas (the upper 1200 m), the transfer of sediments from the Argentinean margin to the north of 35∘ S is limited by the Subtropical Shelf Front and the basin-wide recirculated Antarctic Intermediate Water. On the southern Brazilian inner and middle shelf, it is possible to recognize the northward influence of the Río de la Plata sediments carried by the Plata Plume Water. Another flow responsible for sediment transport and deposition on the outer shelf and slope is the southward flow of the Brazil Current. Finally, we propose that the Brazil–Malvinas Confluence and the Santos Bifurcation act as boundaries of geochemical provinces in the area. A conceptual model of sediment sources and transport is provided for the southwestern Atlantic margin.

scholarly journals A Climatology of Subtropical Cyclones in the South Atlantic

2012 ◽  
Vol 25 (21) ◽  
pp. 7328-7340 ◽  
Author(s):  
Jenni L. Evans ◽  
Aviva Braun
Keyword(s):  
North Atlantic ◽  
Warm Season ◽  
Hybrid Structure ◽  
South Atlantic ◽  
The South ◽  
Rossby Wave Breaking ◽  
The North ◽  
Brazil Current ◽  
Eastern Australia ◽  
Upper Level

A 50-yr climatology (1957–2007) of subtropical cyclones (STs) in the South Atlantic is developed and analyzed. A subtropical cyclone is a hybrid structure (upper-level cold core and lower-level warm core) with associated surface gale-force winds. The tendency for warm season development of North Atlantic STs has resulted in these systems being confused as tropical cyclones (TCs). In fact, North Atlantic STs are a regular source of the incipient vortices leading to North Atlantic TC genesis. In 2004, Hurricane Catarina developed in the South Atlantic and made landfall in Brazil. A TC system had been previously unobserved in the South Atlantic, so the incidence of Catarina highlighted the lack of an ST climatology for the region to provide a context for the likelihood of future systems. Sixty-three South Atlantic STs are documented over the 50-yr period analyzed in this climatology. In contrast to the North Atlantic, South Atlantic STs occur relatively uniformly throughout the year; however, their preferred location of genesis and mechanisms for this genesis do exhibit some seasonal variability. Rossby wave breaking was identified as the mechanism for the ST vortex initiation for North Atlantic STs. A subset of South Atlantic STs forms via this mechanism, however, an additional mechanism for ST genesis is identified here: lee cyclogenesis downstream of the Andes in the Brazil Current region—an area favorable for convection. This formation mechanism is similar to development of type-2 east coast lows in the Tasman Sea off eastern Australia.

Matrilineal Kinship among the Kunda

Africa ◽  
1958 ◽  
Vol 28 (3) ◽  
pp. 207-224 ◽  
Author(s):  
J. P. Van S. Bruwer
Keyword(s):  
Western Boundary ◽  
The South ◽  
Administrative District ◽  
Eastern Province ◽  
The North ◽  
Eastern Boundary ◽  
Game Reserve ◽  
Opening Paragraph

Opening ParagraphThe Kunda, a matrilineal Bantu people numbering about 20,000, occupy part of the Luangwa valley in the Eastern Province of Northern Rhodesia. Their country, located within the administrative district of Fort Jameson, stretches along the east bank of the Luangwa between the Lusangazi in the south and the Lukuzi in the north. Its western boundary is the Luangwa river proper; across the river a game reserve, stretching up from the Muchinga range, forms an uninhabited barrier between them and the tribes beyond the mountains. The eastern boundary is less clearly demarcated, but marches with the territory of the adjacent Cewa. To the south and north live the Nsenga and Bisa respectively. All these adjacent tribes are matrilineal.

scholarly journals Possible origin of the bluetongue epidemic in Cyprus, August 1977

1979 ◽  
Vol 83 (3) ◽  
pp. 547-555 ◽  
Author(s):  
R. F. Sellers ◽  
E. P. J. Gibbs ◽  
K. A. J. Herniman ◽  
D. E. Pedgley ◽  
M. R. Tucker
Keyword(s):  
Domestic Animals ◽  
Disease Spread ◽  
North Coast ◽  
Surface Winds ◽  
The South ◽  
Wind Speeds ◽  
The Past ◽  
The North

Possible origins of an epidemic of bluetongue in Cyprus in August 1977 have been analysed. First outbreaks occurred simultaneously in the south-east of the Famagusta district and on the north coast of the Kyrenia district respectively. Although the epidemic was due to type 4, which had been responsible for the previous outbreak in 1969, no evidence of persistence of virus could be found. Imports of domestic animals in the past year were not implicated since the imported cattle were introduced only to the southern part and not to the northern part of the island. Easterly, north-easterly and northerly winds during the period 11–14 August could have brought infected midges at a height of 0.5–1.5 km from Syria and Turkey, and such a movement would fit well the dates of the first outbreaks (20–25 August). Temperatures at a height of 1.5 km were 20–25 °C and at 0.5 km 30–35 °C, and with wind speeds 10–20 km h−1 the distance from Turkey and Syria would have been covered in 5–20 h. It follows that, in addition to surface winds, winds at all levels warm enough for flight should be taken into account when the possibility of disease spread by windborne midges is being assessed.

scholarly journals Phosphate availability and the ultimate control of new nitrogen input by nitrogen fixation in the tropical Pacific Ocean

2007 ◽  
Vol 4 (4) ◽  
pp. 2407-2440 ◽  
Author(s):  
T. Moutin ◽  
D. M. Karl ◽  
S. Duhamel ◽  
P. Rimmelin ◽  
P. Raimbault ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
N2 Fixation ◽  
Cold Water ◽  
Austral Summer ◽  
Deep Ocean ◽  
South Pacific ◽  
Phosphate Limitation ◽  
The South ◽  
Carbon Export ◽  
The North

Abstract. Due to the low atmospheric input of phosphate into the open ocean, it is one of the key nutrients that could ultimately control primary production and carbon export into the deep ocean. The observed trend over the last 20 years, has shown a decrease in the dissolved inorganic phosphate (DIP) pool in the North Pacific gyre, which has been correlated to the increase in di-nitrogen (N2) fixation rates. Following a NW-SE transect, in the Southeast Pacific during the early austral summer (BIOSOPE cruise), we present data on DIP, dissolved organic phosphate (DOP), and particulate phosphate (PP) pools and DIP turnover times (TDIP) along with N2 fixation rates. We observed a decrease in DIP concentration from the edges to the centre of the gyre. Nevertheless the DIP concentrations remained above 100 nmol L−1 and TDIP were more than a month in the centre of the gyre: DIP availability remained largely above the level required for phosphate limitation. This contrasts with recent observations in the western Pacific Ocean at the same latitude (DIAPALIS cruises) where lower DIP concentrations (<20 nmol L−1) and TDIP<50 h were measured during the summer season. During the BIOSOPE cruise, N2 fixation rates were higher within the cold water upwelling near the Chilean coast. This observation contrasts with recently obtained model output for N2 fixation distribution in the South Pacific area and emphasises the importance of studying the main factors controlling this process. The South Pacific gyre can be considered a High P Low Chlorophyll (HPLC) oligotrophic area, which could potentially support high N2 fixation rates, and possibly carbon dioxide sequestration, if the primary ecophysiological controls, temperature and/or iron availability, were alleviated.

Symmetric Instability in Cross-Equatorial Western Boundary Currents

2021 ◽  
Vol 51 (6) ◽  
pp. 2049-2067
Author(s):  
Fraser W. Goldsworth ◽  
David P. Marshall ◽  
Helen L. Johnson
Keyword(s):  
Water Mass ◽  
Numerical Models ◽  
Western Boundary ◽  
Two Dimensional ◽  
Boundary Current ◽  
The North ◽  
Brazil Current ◽  
North Brazil ◽  
North Brazil Current ◽  
Symmetric Instability

AbstractThe upper limb of the Atlantic meridional overturning circulation draws waters with negative potential vorticity from the Southern Hemisphere into the Northern Hemisphere. The North Brazil Current is one of the cross-equatorial pathways in which this occurs: upon crossing the equator, fluid parcels must modify their potential vorticity to render them stable to symmetric instability and to merge smoothly with the ocean interior. In this work a linear stability analysis is performed on an idealized western boundary current, dynamically similar to the North Brazil Current, to identify features that are indicative of symmetric instability. Simple two-dimensional numerical models are used to verify the results of the stability analysis. The two-dimensional models and linear stability theory show that symmetric instability in meridional flows does not change when the nontraditional component of the Coriolis force is included, unlike in zonal flows. Idealized three-dimensional numerical models show anticyclonic barotropic eddies being spun off as the western boundary current crosses the equator. These eddies become symmetrically unstable a few degrees north of the equator, and their PV is set to zero through the action of the instability. The instability is found to have a clear fingerprint in the spatial Fourier transform of the vertical kinetic energy. An analysis of the water mass formation rates suggest that symmetric instability has a minimal effect on water mass transformation in the model calculations; however, this may be the result of unresolved dynamics, such as secondary Kelvin–Helmholtz instabilities, which are important in diabatic transformation.

The Plans of a New Asylum for East Sussex

1900 ◽  
Vol 46 (195) ◽  
pp. 673-688
Author(s):  
H. Hayes Newington
Keyword(s):  
Water Supply ◽  
County Council ◽  
Western Boundary ◽  
The South ◽  
Railway Station ◽  
Efficient System ◽  
Isle Of Wight ◽  
The North ◽  
General Contour ◽  
Suitable Site

When East Sussex determined a year or two back to build an asylum for its sole use, a Visiting Committee, appointed for the purpose, was fortunate enough to find in the centre of the county a suitable estate which the County Council purchased. It is situated at Hellingly, a village about nine miles north of Eastbourne. The area is four hundred acres, compact, as you will see on the plan, having within 400 yards of its western boundary a railway station which we propose to connect with the main asylum by a full gauge tramway. It slopes gently upwards from the south towards the north, where it attains its highest level of about 130 feet above the sea. The subsoil is most favourable, being, with the exception of two patches of clay, of a sandy or gravelly nature. The water supply is adequate, and the general contour lends itself readily to an efficient system of drainage, which will be bacterial. The views are excellent, extending to the sea and the south downs. It would be difficult to find a more suitable site for an asylum. A sub-committee was authorised to travel about the country to inspect other asylums, I being appointed its chairman. We visited the Hartwood, Lenzie, Gartloch, Hawkhead, Cheddleton, Burntwood, Glamorgan, Dorchester, Isle of Wight, and Chichester Asylums.

scholarly journals A stable Faroe Bank Channel overflow 1995–2015

Ocean Science ◽  
2016 ◽  
Vol 12 (6) ◽  
pp. 1205-1220 ◽  
Author(s):  
Bogi Hansen ◽  
Karin Margretha Húsgarð Larsen ◽  
Hjálmar Hátún ◽  
Svein Østerhus
Keyword(s):  
World Ocean ◽  
Deep Ocean ◽  
Acoustic Doppler Current Profiler ◽  
Narrow Channel ◽  
Volume Transport ◽  
Meridional Overturning Circulation ◽  
The Arctic ◽  
Positive Trend ◽  
The North ◽  
Current Profiler

Abstract. The Faroe Bank Channel (FBC) is the deepest passage across the Greenland–Scotland Ridge (GSR) and there is a continuous deep flow of cold and dense water passing through it from the Arctic Mediterranean into the North Atlantic and further to the rest of the world ocean. This FBC overflow is part of the Atlantic Meridional Overturning Circulation (AMOC), which has recently been suggested to have weakened. From November 1995 to May 2015, the FBC overflow has been monitored by a continuous ADCP (acoustic Doppler current profiler) mooring, which has been deployed in the middle of this narrow channel. Combined with regular hydrography cruises and several short-term mooring experiments, this allowed us to construct time series of volume transport and to follow changes in the hydrographic properties and density of the FBC overflow. The mean kinematic overflow, derived solely from the velocity field, was found to be (2.2 ± 0.2) Sv (1 Sv  =  106 m3 s−1) with a slight, but not statistically significant, positive trend. The coldest part, and probably the bulk, of the FBC overflow warmed by a bit more than 0.1 °C, especially after 2002, increasing the transport of heat into the deep ocean. This warming was, however, accompanied by increasing salinities, which seem to have compensated for the temperature-induced density decrease. Thus, the FBC overflow has remained stable in volume transport as well as density during the 2 decades from 1995 to 2015. After crossing the GSR, the overflow is modified by mixing and entrainment, but the associated change in volume (and heat) transport is still not well known. Whatever effect this has on the AMOC and the global energy balance, our observed stability of the FBC overflow is consistent with reported observations from the other main overflow branch, the Denmark Strait overflow, and the three Atlantic inflow branches to the Arctic Mediterranean that feed the overflows. If the AMOC has weakened during the last 2 decades, it is not likely to have been due to its northernmost extension – the exchanges across the Greenland–Scotland Ridge.

scholarly journals Assimilation of Radiocarbon and Chlorofluorocarbon Data to Constrain Deep and Bottom Water Transports in the World Ocean

2007 ◽  
Vol 37 (2) ◽  
pp. 259-276 ◽  
Author(s):  
Reiner Schlitzer
Keyword(s):  
Southern Ocean ◽  
North Atlantic ◽  
Bottom Water ◽  
World Ocean ◽  
Weddell Sea ◽  
Global Ocean ◽  
Western Boundary ◽  
Boundary Current ◽  
The North ◽  
The North Atlantic

Abstract A coarse-resolution global model with time-invariant circulation is fitted to hydrographic and tracer data by means of the adjoint method. Radiocarbon and chlorofluorocarbon (CFC-11 and CFC-12) data are included to constrain deep and bottom water transport rates and spreading pathways as well as the strength of the global overturning circulation. It is shown that realistic global ocean distributions of hydrographic parameters and tracers can be obtained simultaneously. The model correctly reproduces the deep ocean radiocarbon field and the concentrations gradients between different basins. The spreading of CFC plumes in the deep and bottom waters is simulated in a realistic way, and the spatial extent as well as the temporal evolution of these plumes agrees well with observations. Radiocarbon and CFC observations place upper bounds on the northward transports of Antarctic Bottom Water (AABW) into the Pacific, Atlantic, and Indian Oceans. Long-term mean AABW transports larger than 5 Sv (Sv ≡ 106 m3 s−1) through the Vema and Hunter Channels in the South Atlantic and net AABW transports across 30°S into the Indian Ocean larger than 10 Sv are found to be incompatible with CFC data. The rates of equatorward deep and bottom water transports from the North Atlantic and Southern Ocean are of similar magnitude (15.7 Sv at 50°N and 17.9 Sv at 50°S). Deep and bottom water formation in the Southern Ocean occurs at multiple sites around the Antarctic continent and is not confined to the Weddell Sea. A CFC forecast based on the assumption of unchanged abyssal transports shows that by 2030 the entire deep west Atlantic exhibits CFC-11 concentrations larger than 0.1 pmol kg−1, while most of the deep Indian and Pacific Oceans remain CFC free. By 2020 the predicted CFC concentrations in the deep western boundary current (DWBC) in the North Atlantic exceed surface water concentrations and the vertical CFC gradients start to reverse.

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