Brazil-Malvinas Confluence
Encyclopedia
The Brazil-Malvinas Confluence Zone is a very energetic region of water just off the coast of Argentina
and Uruguay
where the warm poleward flowing Brazil Current
and the cold equatorward flowing Malvinas Current converge. This region does oscillate latitudinally, however, in general this region of confluence
occurs between 35 and 45 degrees South latitude and 50 to 70 degrees West longitude. The confluence of these two currents causes a strong thermohaline
to exist and causes numerous high energy eddies
to form. Figure 1 illustrates the location and sea surface temperature contrasts between the Brazil Current and Malvinas Current.
water. The Brazil Current branches off northward from the South Equatorial Current
at around 10 degrees South. As it flows poleward it branches off into two pieces at around 22 degrees South. One part flows eastward, and the other portion continues the poleward march flowing along the South American continental shelf
. The poleward directed branch is the current that comes into convergence with the Malvinas Current. Typical temperature values for the Brazil Current are between 18 and 28 degrees celsius, decreasing as it moves poleward. Typical salinities
for the Brazil Current range between 35 and 36psu with some isolated spots as high as 37psu. The current typically flows in the upper 600 meters of the ocean and its volume transport as it reaches the confluence zone is upwards of 20 Sverdrup
s with speeds over a half a meter per second. Figure 2 shows the Brazil Current.
water. The Malvinas Current is a branch off of the Antarctic Circumpolar Current
. It transports between 60 and 90 Sverdrups of water with speeds ranging from a half a meter to a meter per second. Hydrographic data in this area is very scarce and thus various hydrographic variables have a great deal of error. It is interesting to note that the Malvinas Current is not simply a surface current like the Brazil Current but actually extends all the way to the sea-floor. Typical temperatures for the current are around 6 degrees Celsius with a salinity between 33.5 and 34.5psu. Figure 3 shows the Malvinas Current.
es in the Brazil-Malvinas Confluence Zone. These various water masses help contribute even more to this very complex dynamical confluence zone. Starting at the surface (<800m) where the Brazil Current is carrying Subtropical Surface Water and the Malvinas Current is carrying Subantarctic Surface Water, after these two surfaces collide they mix some, but in general they develop strong thermohaline fronts due to the strong difference in temperature
and salinity. Below the surface from about 800 meters to 1500 meters there is Antarctic Intermediate Water
that is flowing equatorward. At the very bottom of the Brazil-Malvinas Confluence Zone there is equatorward flowing Weddell Sea
Deep Water. Between the Antarctic Intermediate Water and the Weddel Sea Deep Water there are three different water masses flowing poleward: North Atlantic Deep Water
, Lower Circumpolar Deep Water, and Upper Circumpolar Deep Water.
s have been able to give us a better idea of what this flow looks like. After the Brazil Current collides with the Malvinas Current at around 38 degrees South, it branches off into two different paths. The first path gets redirected back equatorward and actually creates a large anticyclonic
eddy with the original Brazil Current. The second path of the Brazil Current, which is much stronger than the aforementioned redirected path, is deflected about 45 degrees east of its original tract poleward.
The surface flow for the Malvinas Current after the collision with the Brazil Current is much simpler than that of the Brazil Current. Once the Malvinas Current collides with the Brazil Current at the Brazil-Malvinas Confluence Zone the Malvinas Current gets redirected poleward. It will continue to follow this poleward tract till about 50 degrees South latitude where it will once again be picked back up by the Antarctic Circumpolar Current and head East. Figure 4 has a great illustration of the paths of the Brazil and Malvinas Currents following the collision.
The temperature and salinity gradients that are generated by the Brazil-Malvinas Confluence Zone are amazing. The southeast deflected Brazil Current flows just east of the redirected Malvinas current at around 57.5W and between 40 and 45S (See fig. 4). In this region sea surface temperature gradients can be as high as 1 degree C per kilometer. Salinity gradients are also extraordinarily high in this region.
The meander
s, eddies, and filaments created in this confluence zone are extraordinary. The eddies exhibit strong rotational velocities and are extremely energetic. At any given time there could be 8 or 9 distinct mesoscale
eddies with many other microscale eddies existing at the same time. There is a lot of research going into the study of these high energy turbulent mixing areas, but it is still far too early to understand these mesoscale processes in depth.
s while the Brazil Current supplies warm ocean temperatures. Intense vertical mixing in these zones create a very fertile area for the production of biological species. This zone is looked at as a major atmospheric carbon sink due to the amount of primary production that takes place here which is vitally important in our changing climate. Figure 5 shows chlorophyll
-a concentration in this zone.
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
and Uruguay
Uruguay
Uruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...
where the warm poleward flowing Brazil Current
Brazil Current
The Brazil Current is a warm water current that flows south along the Brazilian south coast to the mouth of the Río de la Plata. This current is caused by diversion of a portion of the Atlantic South Equatorial Current from where that current meets the South American continent...
and the cold equatorward flowing Malvinas Current converge. This region does oscillate latitudinally, however, in general this region of confluence
Confluence
Confluence, in geography, describes the meeting of two or more bodies of water.Confluence may also refer to:* Confluence , a property of term rewriting systems...
occurs between 35 and 45 degrees South latitude and 50 to 70 degrees West longitude. The confluence of these two currents causes a strong thermohaline
Thermohaline circulation
The term thermohaline circulation refers to a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes....
to exist and causes numerous high energy eddies
Eddy (fluid dynamics)
In fluid dynamics, an eddy is the swirling of a fluid and the reverse current created when the fluid flows past an obstacle. The moving fluid creates a space devoid of downstream-flowing fluid on the downstream side of the object...
to form. Figure 1 illustrates the location and sea surface temperature contrasts between the Brazil Current and Malvinas Current.
Brazil Current
The Brazil Current is a poleward flowing current that carries warm subtropicalSubtropics
The subtropics are the geographical and climatical zone of the Earth immediately north and south of the tropical zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitudes 23.5°N and 23.5°S...
water. The Brazil Current branches off northward from the South Equatorial Current
South Equatorial Current
The South Equatorial Current is a significant Pacific, Atlantic, and Indian Ocean current that flows east-to-west between the equator and about 20 degrees south. In the Pacific and Atlantic Oceans, it extends across the equator to about 5 degrees north....
at around 10 degrees South. As it flows poleward it branches off into two pieces at around 22 degrees South. One part flows eastward, and the other portion continues the poleward march flowing along the South American continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
. The poleward directed branch is the current that comes into convergence with the Malvinas Current. Typical temperature values for the Brazil Current are between 18 and 28 degrees celsius, decreasing as it moves poleward. Typical salinities
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
for the Brazil Current range between 35 and 36psu with some isolated spots as high as 37psu. The current typically flows in the upper 600 meters of the ocean and its volume transport as it reaches the confluence zone is upwards of 20 Sverdrup
Sverdrup
The sverdrup, named in honour of the pioneering oceanographer Harald Sverdrup, is a unit of measure of volume transport. It is used almost exclusively in oceanography, to measure the transport of ocean currents. Its symbol is Sv. Note that the sverdrup is not an SI unit, and that its symbol...
s with speeds over a half a meter per second. Figure 2 shows the Brazil Current.
Malvinas Current
The Malvinas Current is an equatorward flowing current that carries cold and relatively fresh subantarcticSubantarctic
The Subantarctic is a region in the southern hemisphere, located immediately north of the Antarctic region. This translates roughly to a latitude of between 46° – 60° south of the Equator. The subantarctic region includes many islands in the southern parts of the Indian Ocean, Atlantic Ocean and...
water. The Malvinas Current is a branch off of the Antarctic Circumpolar Current
Antarctic Circumpolar Current
The Antarctic Circumpolar Current is an ocean current that flows from west to east around Antarctica. An alternative name for the ACC is the West Wind Drift. The ACC is the dominant circulation feature of the Southern Ocean and, at approximately 125 Sverdrups, the largest ocean current...
. It transports between 60 and 90 Sverdrups of water with speeds ranging from a half a meter to a meter per second. Hydrographic data in this area is very scarce and thus various hydrographic variables have a great deal of error. It is interesting to note that the Malvinas Current is not simply a surface current like the Brazil Current but actually extends all the way to the sea-floor. Typical temperatures for the current are around 6 degrees Celsius with a salinity between 33.5 and 34.5psu. Figure 3 shows the Malvinas Current.
Water Masses in Confluence Zone
There are a total of seven different water massWater mass
An oceanographic water mass is an identifiable body of water with a common formation history which has physical properties distinct from surrounding water...
es in the Brazil-Malvinas Confluence Zone. These various water masses help contribute even more to this very complex dynamical confluence zone. Starting at the surface (<800m) where the Brazil Current is carrying Subtropical Surface Water and the Malvinas Current is carrying Subantarctic Surface Water, after these two surfaces collide they mix some, but in general they develop strong thermohaline fronts due to the strong difference in temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
and salinity. Below the surface from about 800 meters to 1500 meters there is Antarctic Intermediate Water
Antarctic Intermediate Water
Antarctic Intermediate Water is a cold, relatively low salinity water mass found mostly at intermediate depths in the Southern Ocean. The AAIW is formed at the ocean surface in the Antarctic Convergence zone or more commonly called the Antarctic Polar Front zone...
that is flowing equatorward. At the very bottom of the Brazil-Malvinas Confluence Zone there is equatorward flowing Weddell Sea
Weddell Sea
The Weddell Sea is part of the Southern Ocean and contains the Weddell Gyre. Its land boundaries are defined by the bay formed from the coasts of Coats Land and the Antarctic Peninsula. The easternmost point is Cape Norvegia at Princess Martha Coast, Queen Maud Land. To the east of Cape Norvegia is...
Deep Water. Between the Antarctic Intermediate Water and the Weddel Sea Deep Water there are three different water masses flowing poleward: North Atlantic Deep Water
North Atlantic Deep Water
North Atlantic Deep Water is a water mass that forms in the North Atlantic Ocean. It is largely formed in the Labrador Sea and in the Greenland Sea by the sinking of highly saline, dense overflow water from the Greenland Sea...
, Lower Circumpolar Deep Water, and Upper Circumpolar Deep Water.
Surface Flow and Thermohaline Gradients in the Confluence Zone
The surface flow in the Brazil-Malvinas Confluence Zone is still not quite well understood, but more recently satelliteSatellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
s have been able to give us a better idea of what this flow looks like. After the Brazil Current collides with the Malvinas Current at around 38 degrees South, it branches off into two different paths. The first path gets redirected back equatorward and actually creates a large anticyclonic
Anticyclone
An anticyclone is a weather phenomenon defined by the United States' National Weather Service's glossary as "[a] large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere"...
eddy with the original Brazil Current. The second path of the Brazil Current, which is much stronger than the aforementioned redirected path, is deflected about 45 degrees east of its original tract poleward.
The surface flow for the Malvinas Current after the collision with the Brazil Current is much simpler than that of the Brazil Current. Once the Malvinas Current collides with the Brazil Current at the Brazil-Malvinas Confluence Zone the Malvinas Current gets redirected poleward. It will continue to follow this poleward tract till about 50 degrees South latitude where it will once again be picked back up by the Antarctic Circumpolar Current and head East. Figure 4 has a great illustration of the paths of the Brazil and Malvinas Currents following the collision.
The temperature and salinity gradients that are generated by the Brazil-Malvinas Confluence Zone are amazing. The southeast deflected Brazil Current flows just east of the redirected Malvinas current at around 57.5W and between 40 and 45S (See fig. 4). In this region sea surface temperature gradients can be as high as 1 degree C per kilometer. Salinity gradients are also extraordinarily high in this region.
The meander
Meander
A meander in general is a bend in a sinuous watercourse. A meander is formed when the moving water in a stream erodes the outer banks and widens its valley. A stream of any volume may assume a meandering course, alternately eroding sediments from the outside of a bend and depositing them on the...
s, eddies, and filaments created in this confluence zone are extraordinary. The eddies exhibit strong rotational velocities and are extremely energetic. At any given time there could be 8 or 9 distinct mesoscale
Mesoscale
Mesoscale may refer to:* Mesoscale meteorology* Mesoscopic scale in physics...
eddies with many other microscale eddies existing at the same time. There is a lot of research going into the study of these high energy turbulent mixing areas, but it is still far too early to understand these mesoscale processes in depth.
Current research
Current research is focusing in on trying to better observe the Brazil-Malvinas Confluence Zone so the dynamics of this system can be better explained. Right now there only exists images of these small scale dynamical process (e.g. eddies), however, numerical interpretation of these eddies are still very much in the beginning stages of our understanding. The other major area of research is focusing in on the biological productivity in this region. This confluence zone is such a "hot spot" for primary production because the Malvinas Current supplies a lot of nutrientNutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...
s while the Brazil Current supplies warm ocean temperatures. Intense vertical mixing in these zones create a very fertile area for the production of biological species. This zone is looked at as a major atmospheric carbon sink due to the amount of primary production that takes place here which is vitally important in our changing climate. Figure 5 shows chlorophyll
Chlorophyll
Chlorophyll is a green pigment found in almost all plants, algae, and cyanobacteria. Its name is derived from the Greek words χλωρος, chloros and φύλλον, phyllon . Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to obtain energy from light...
-a concentration in this zone.