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North Equatorial Current

North Equatorial Current is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand North Equatorial Current rather than just read about it. In short: The North Equatorial Current (NEC) is a westward wind-driven current mostly located near the equator, but the location varies from different oceans. The NEC in the Pacific and the Atlantic is about 5°-20°N, while the NEC in the Indian Ocean is very close to the equator.

North Equatorial Current — main illustration
North Equatorial Current — illustration

Key takeaways

  • North Equatorial Current belongs to earth science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect North Equatorial Current to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of North Equatorial Current from memory before moving on to harder problems.

Reference excerpt

The North Equatorial Current (NEC) is a westward wind-driven current mostly located near the equator, but the location varies from different oceans. The NEC in the Pacific and the Atlantic is about 5°-20°N, while the NEC in the Indian Ocean is very close to the equator. It ranges from the sea surface down to 400 m in the western Pacific.

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 is aligned to the location of the Intertropical Convergence Zone (ITCZ), which is the area that the northeast and the southeast trade wind converge.

Related processes

The Equatorial Counter Current 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, 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 The Ekman transport 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 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.

Interaction with climate The NEC, 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.

In different oceans

Pacific NEC

The NEC is evident around 10°-18°N across 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 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 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.

Atlantic NEC

The NEC in the Atlantic is evident around 10°-20°N, spanning the longitude from 16°-60°W. The typical flow velocity 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 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 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 the Atlantic Multidecadal Oscillation (AMO).

The Indian Ocean NEC

… excerpt ends here. Continue reading the full article.

Illustrations

North Equatorial Current: North Equatorial Current (in black labeled N. Equatorial)
North Equatorial Current (in black labeled N. Equatorial)
North Equatorial Current: a) and b) show the mean zonal surface velocity in Pacific during El Niño (1997) and La Niña years (1998). Positive values (red) represent eastward flow, negative values (blue) for westward flow. All the data plotted in this article is obtained from the GODAS dataset.[2]
a) and b) show the mean zonal surface velocity in Pacific during El Niño (1997) and La Niña years (1998). Positive values (red) represent eastward flow, negative values (blue) for westward flow. All the data plotted in this article is obtained from the GODAS dataset.[2]
North Equatorial Current: a) shows the mean zonal surface currents within the Atlantic in the first half-year (Jan-Jun) of 1997. b) shows the second half (Jul-Dec). These two figures show a strong seasonality, with NECC stronger during July to December. Positive values (red) represent eastward flow, negative values (blue) for westward flow.
a) shows the mean zonal surface currents within the Atlantic in the first half-year (Jan-Jun) of 1997. b) shows the second half (Jul-Dec). These two figures show a strong seasonality, with NECC stronger during July to December. Positive values (red) represent eastward flow, negative values (blue) for westward flow.
North Equatorial Current: This figure shows the mean zonal surface current of different periods in the Indian Ocean. a), b) and c) are currents during January and February, during July and August, and in May, respectively. Positive values (red) represent eastward flow, negative values (blue) for westward flow.
This figure shows the mean zonal surface current of different periods in the Indian Ocean. a), b) and c) are currents during January and February, during July and August, and in May, respectively. Positive values (red) represent eastward flow, negative values (blue) for westward flow.

Worked examples

Example 1 — a first encounter with North Equatorial Current

Start with the simplest possible case. Write down what North Equatorial Current claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to North Equatorial Current before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about North Equatorial Current ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of North Equatorial Current

In research
North Equatorial Current appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses North Equatorial Current in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
North Equatorial Current is common in secondary-school and first-year university syllabi. It links to neighbouring topics Currents of the Atlantic Ocean, Currents of the Pacific Ocean, so understanding it makes those chapters shorter.
In everyday life
Look for North Equatorial Current outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study North Equatorial Current in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what North Equatorial Current means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain North Equatorial Current out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is North Equatorial Current in simple terms?

The North Equatorial Current (NEC) is a westward wind-driven current mostly located near the equator, but the location varies from different oceans. The NEC in the Pacific and the Atlantic is about 5°-20°N, while the NEC in the Indian Ocean is very close to the equator.

Why does North Equatorial Current matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study North Equatorial Current?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on North Equatorial Current.

Tags

  • Currents of the Atlantic Ocean
  • Currents of the Pacific Ocean

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