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27-518: The NEC is driven by the north-hemisphere easterly trade wind. In couple with NEC, there is another current called South Equatorial Current ( SEC ), generated by the easterly trade wind in the southern hemisphere. Despite the well-coupled name of the two equatorial currents, the distribution of the NEC and the SEC is not in symmetry at the equator, but slightly northward to the equator. This asymmetric distribution

54-538: A rather complicated process that includes western boundary current intensification. On the equator, the South Equatorial Current is driven directly by the trade winds which blow from east to west. In the Indian Ocean, the westward-flowing South Equatorial Current is well-developed only south of the equator. Directly on the equator, the winds reverse twice a year due to the monsoons, and so

81-402: Is a wind-driven transport. It occurs due to the rotation of the globe. A transport is found to the right of the flow direction in the northern hemisphere, while to the left of the flow in the southern hemisphere. It is noteworthy that in the tropical regions, where NEC and SEC both flow to the west, a northward Ekman transport in the NEC and a southward Ekman transport in the SEC take place. Due to

108-457: Is about 10 c m ⋅ s − 1 {\displaystyle 10cm\cdot s^{-1}} , lower than in the Pacific. Instead of interannual variability, the NEC shows a strong seasonality, in which NECC is stronger from July to December, weaker from January to June. Besides, the NEC is more equatorward from January to June. The NEC splits into two after reaching

135-695: Is aligned to the location of the Intertropical Convergence Zone (ITCZ) , which is the area that the northeast and the southeast trade wind converge. The NEC and the SEC will generate an Equatorial Counter Current ( ECC ), named as the North Equatorial Counter Current (NECC) in both Pacific and Atlantic and the South Equatorial Counter Current (SECC) in the Indian Ocean. The NEC and SEC continuously flow westward. However,

162-650: The Atlantic Multidecadal Oscillation (AMO) . The NEC in the Indian ocean is strongly affected by the continent to the north. The NEC is more southward than the other two oceans, which drives the Equatorial Counter Current to the southern hemisphere. So, the counter current is called South Equatorial Counter Current (SECC) here. The NEC sits right on the equator, across a longitude from 45°-100°E. The typical speed in

189-663: The NEC, also known as the Ekman transport, is evident northward at any location all the way along with itself. When the current reaches the west end, the Philippines, it splits into two western boundary flows . One of the branches flows poleward feeding the Kuroshio Current , another one flows equatorward feeding the Mindanao Current . This North Equatorial Current Bifurcation (NECB) plays an important role in

216-477: The NEC. The current flows faster in the thinner layer. Another reason is due to the smaller Coriolis effect at the equator. The NEC, thus, is more aligned to the westward wind on the equator. The NEC shows a very strong seasonal pattern. During January and February, thanks to the prevailing northeast wind, the NEC travels all the way to the east coast of Somalia and joins the Somali Current flowing towards

243-483: The Pacific, Atlantic, and Indian Ocean that flow 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 . Within the southern hemisphere, the South Equatorial Current is the westward limb of the very large-scale subtropical gyres. These gyres are driven by the combination of trade winds in the tropics and westerly winds that are found south of about 30 degrees south , through

270-537: The SEC and the ECC play an important role in the climate system causing various of climate patterns, such as El Niño–Southern Oscillation (ENSO) , the Atlantic Meridional Mode (AMM), the Atlantic Multidecadal Oscillation (AMO) and the seasonal monsoon in the Indian ocean. Reversely, the climate motion also affects the behavior of the equatorial current itself. The NEC is evident around 10°-18°N across

297-550: The coast and curve back into itself . Since the current can be quite large, it is easy for large anticyclonic rings to generate, which separate from the main mass of the current and move northwestward with the prevailing winds. The mean diameter of the rings is about 300 kilometers, and move between 8 and 30 kilometers per day depending on the strength of the flow surrounding the ring. The rings are relatively shallow and move typically less than 1 Sv of water. The rings will eventually spin down after 100 days. Most rings make it to within

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324-564: The coastline of north Brazil. It ends at the border of Brazil and Guiana , where it is renamed the Guiana Current. It is predominantly a salt water current, but it does help transport fresh water from the Amazon River northward. The current begins around 10°S and 31°W, where the split of the South Equatorial Current becomes apparent. The split is forced once the continental shelf begins, and happens quite abruptly. At this point,

351-495: The current moves quite quickly at 21-23 Sv . Around 5°S, it merges with a northern branch of the South Equatorial Current (SEC) and increases its volume to 37 Sv, with its peak between 100m and 200m deep. Here, the current is at its maximum extent of about 300 kilometers wide. The current continues to about 7°N and 52°W, where it becomes the Guiana Current. The general speed of the current is between 60 and 100 centimeters per second. A peak recorded speed of 110 centimeters per second

378-517: The depth is greater than 400 meters, the thermocline acts as the lower limit, and represents the boundary of the NBC and the colder, eastward moving Atlantic North Equatorial Undercurrent (NEU). Since the NEU is colder than the NBC, they will have different densities and not mix, allowing each to flow past each other mostly uninhibited. From July to February, it is quite common for the current to separate from

405-412: The easterlies strengthen. The average is about 26 Sv for the whole year. The average salinity of the current occurs at about 5°S, where the more saline SEC merges with the NBC. Both are quite warm, so the densities are similar, and the currents mix and create water with a salinity of 37.1 psu . The salinity will then decrease to around 36.5 psu as the current moves northward toward the equator and into

432-565: The entire Pacific basin, from the Philippines to Nicaragua . Its typical zonal velocity is 30 c m ⋅ s − 1 {\displaystyle 30cm\cdot s^{-1}} . The NEC shows little seasonal variability, but an interannual instability. The interannual instability of the NEC is strongly linked to ENSO . The NEC strengthens in La Niña years and weakens in El Niño years. The meridional component of

459-435: The fact that the Ekman transport is perpendicular to the flow itself, these Ekman transports contribute to the meridional branch of the NEC and SEC. However, the magnitude of the meridional component is of no comparison to the current itself. Another subsequent result of the Ekman transport is the upwelling , which occurs in between the NEC and the SEC, where a massive water divergence at the sea surface takes place. The NEC,

486-545: The heat transport is responsible for the tropical sea temperature anomaly. The temperature anomaly at the sea surface is a possible cause that leads to Atlantic hurricane season. On the interannual and longer timescales, the equatorial and tropical Atlantic ocean has a strong interaction with the dynamics of several patterns of variabilities, the Atlantic Niño, the Atlantic Meridional Mode (AMM) and

513-641: The north of South America, joining the North Brazil Current (NBC) and the NECC respectively. The northward meridional Ekman transport dominates the tropical Atlantic Ocean, playing a very important role in the northward heat transport. This strong northward surface transport is well known as the upper component of the Atlantic Meridional Overturning Circulation (AMOC) . On a seasonal time scale, variability of

540-458: The presence of the Intertropical Convergence Zone (ITCZ). The rainfall produced at the ITCZ works to dilute the salt content of the water. The depth of the NBC is dependent on the depth of the thermocline , as well as the depth of the continental shelf . Closer to the shore, and especially where the depth of the water is less than 400 m, the sea floor acts as the lower limit to the current. If

567-571: The prevailing southwest wind in the summer, the surface waters move from the southern Arabian Sea to the southern Bay of Bengal . During the transition of these two phases, specifically around May and November, the NEC becomes very weak, almost invisible in Figure 3. Instead of the NEC, a strong eastward current is found near the equator, known as the Wyrtki jets . South Equatorial Current The South Equatorial Current are ocean currents in

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594-423: The seawater does not just pile up at the west basin surface. The advent water must have gone back to the east by some means. The Sverdrup balance can partly explain where the water ends up at. When the NEC and the SEC reached the west end of a basin, some of the water travels poleward to join the low-latitude circulations, while some travels equatorward to join the Equatorial Counter Current . The Ekman transport

621-549: The south Asian climate system. As currently, climate change is more and more evident, thus, leading to a more amplified migration of the NECB. As a result, this amplification of the migration may lead to redistribution of the water mass and heat transport along the western boundary, and thus warm pool and monsoon climate. The NEC in the Atlantic is evident around 10°-20°N, spanning the longitude from 16°-60°W. The typical flow velocity

648-523: The southwest to feed the SECC. As a result, SECC is strong during the winter. And at this time, the NEC carries surface waters from the southern Bay of Bengal to the southern Arabian Sea . While during July and August, the location of the NEC moves southward and the Somali Current reverses. As a result, the NEC and the SEC feed Somali Current instead of the SECC. So, the SECC becomes very weak. Due to

675-438: The surface current can be either eastward or westward. This article about a specific ocean current is a stub . You can help Misplaced Pages by expanding it . North Brazil Current The North Brazil Current (NBC) is a warm water ocean current that is part of the southwestern North Atlantic Gyre . It begins when the westward moving Atlantic South Equatorial Current splits in half and flows northwestward, following

702-429: The winter can reach up to 50 c m ⋅ s − 1 {\displaystyle 50cm\cdot s^{-1}} , thanks to the northeast seasonal wind from the continent. In the Indian Ocean, the NEC is faster than the SEC. Multiple reasons are considered. The equator-located NEC receives more solar heat than the more poleward-located SEC, which leads to a much denser but thinner upper layer for

729-413: Was recorded about 100 m below the surface of the ocean, in the vicinity of where the NBC merges with the SEC. Average temperatures are in the range of 22 °C to 28.5 °C, and tend to be warmest during the northern hemisphere's summer . The strength of the current is dependent on the season. During the northern hemisphere's spring, there is a minimum of 13 Sv in the current, which jumps to 36 Sv as

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