The sources of the Agulhas Current are the
East Madagascar Current (25 Sv), the
Mozambique Current (5 Sv) and a recirculated part of the south-west Indian subgyre south of Madagascar (35 Sv). The net transport of the Agulhas Current is estimated as 100 Sv. The flow of the Agulhas Current is directed by the
topography. The current follows the
continental shelf from
Maputo to the tip of the
Agulhas Bank (250 km south of
Cape Agulhas). Here the momentum of the current overcomes the
vorticity balance holding the current to the topography and the current leaves the shelf. The current reaches its maximum transport near the Agulhas Bank where it ranges between 95 and 136 Sv. The core of the current is defined as where the surface velocities reach , which gives the core an average width of . The mean peak speed is , but the current can reach . The AC passes offshore and an ACM can reach offshore. When the AC meanders, its width broadens from to and its velocity weakens from to . An ACM induces a strong inshore counter-current. Large-scale cyclonic meanders known as Natal pulses are formed as the Agulhas Current reaches the continental shelf on the South African east-coast (i.e. the eastern Agulhas Bank off
Natal). As these pulses moves along the coast on the Agulhas Bank, they tend to pinch off Agulhas rings from the Agulhas Current. Such a
ring shedding can be triggered by a Natal pulse alone, but sometimes meanders on the
Agulhas Return Current merge to contribute to the shedding of an Agulhas ring.
Retroflection In the southeast
Atlantic Ocean the current
retroflects (turns back on itself) in the
Agulhas Retroflection due to shear interactions with the strong
Antarctic Circumpolar Current, also known as the "
West Wind Drift" despite referring to the ocean current rather than to the surface winds. This water becomes the Agulhas Return Current, rejoining the
Indian Ocean Gyre. It is estimated that up to 85 Sv (Sv) of the net transport is returned to the
Indian Ocean through the retroflection. The remaining water is transported into the
South Atlantic Gyre in the Agulhas Leakage. Along with direct branch currents, this leakage takes place in surface water filaments, and Agulhas Eddies.
Agulhas leakage and rings where it retroflects back into the Indian Ocean. It is estimated that as much as 15 Sv of
Indian Ocean water is leaked directly into the
South Atlantic. 10 Sv of this is relatively warm, salty
thermocline water, with the remaining 5 Sv being cold, low salinity
Antarctic Intermediate Water. Since Indian Ocean water is significantly warmer (24-26 °C) and saltier than South Atlantic water, the Agulhas Leakage is a significant source of salt and heat for the South Atlantic Gyre. This heat flux is believed to contribute to the high rate of evaporation in the South Atlantic, a key mechanism in the
Meridional Overturning Circulation. A small amount of the Agulhas Leakage joins the
North Brazil Current, carrying Indian Ocean water into the
North Atlantic Subtropical Gyre. Surface water filaments are estimated to account for up to 13% of the total salt transport from the Agulhas Current into the
Benguela Current and South Atlantic Gyre. Due to surface dissipation, these filaments are not believed to significantly contribute to inter-basin heat flux. The provenance of ocean sediments can be determined by analysing
terrigenous strontium isotope ratios in deep ocean cores. Sediments underlying the Agulhas Current and Return Current have significantly higher ratios than surrounding sediments. Franzese et al. 2009 analysed cores in the South Atlantic deposited during the
Last Glacial Maximum (LGM, 20 000 years ago), and concluded that the Agulhas leakage was significantly reduced. The trajectory of the current was the same during the LGM and that the reduced leakage must be explained by a weaker current. Furthermore, it can be predicted that a stronger Agulhas Current will result in a more eastward retroflection and an increased Agulhas leakage. , however, noted that changes in temperature and salinity in the Agulhas leakage is at least partly the result of variability in the composition in the current itself and can be a poor indicator of the strength of the leakage.
Rogue waves The south-east coast of South Africa is on the main shipping route between the Middle-East and Europe/the U.S. and even large ships have sustained major damage because of
rogue waves in the area where these waves occasionally can reach a height of more than . Some 30 larger ships were severely damaged or sunk by rogue waves along the South African east-coast between 1981 and 1991.
Agulhas Undercurrent Directly under the core of the Agulhas Current, at a depth of , there is an Agulhas Undercurrent which flows equatorward. The undercurrent is deep and wide and can reach at , one of greatest speeds observed in any current at this depth, but it also displays a great variance with a transport of 4.2±5.2 Sv. The undercurrent can represent as much as 40% of the Indian Ocean
overturning transport. Below a separate layer of the undercurrent can be distinguished: the more coherent
North Atlantic Deep Water (NADW) which transports an average of 2.3±3.0 Sv. The periodicity of the meanders and Natal pulses of the Agulhas is matched by the Agulhas Undercurrent. More research is needed but observations seem to indicate that during a meander event the Agulhas moves first onshore, then offshore, and finally onshore again, first weakening then strengthening 10-15 Sv. At the same time the undercurrent is first squeezed offshore and weakened when the Agulhas moves onshore, then strengthened and forced upward when the Agulhas moves offshore, and finally returns to normal. ==Biological properties==