earth science

Retroflect

Retroflect 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 Retroflect rather than just read about it. In short: Retroflection is the movement of an ocean current that doubles back on itself. Usage history More commonly used to describe the way the mammalian intestine or uterus might turn back on itself, retroflection was first used in an oceanographic sense in 1970 by South African oceanographer Nils Bang, to describe the Agulhas Current which curves on itself at the southern tip of Africa to become the Agulhas Return Current.

Key takeaways

Retroflect 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 Retroflect to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Retroflect from memory before moving on to harder problems.

Reference excerpt

Retroflection is the movement of an ocean current that doubles back on itself.

Usage history More commonly used to describe the way the mammalian intestine or uterus might turn back on itself, retroflection was first used in an oceanographic sense in 1970 by South African oceanographer Nils Bang, to describe the Agulhas Current which curves on itself at the southern tip of Africa to become the Agulhas Return Current. Bang credited the inspiration for the metaphor to his wife, Alison Coombe Bang, a nursing sister, who mentioned the term during her midwifery studies. Bang's research, through the University of Cape Town, was done on a limited budget and with rudimentary equipment, yet his studies using closely spaced bathythermograph readings, were later corroborated by satellite thermal imagery. The term was then revived and is now common parlance among oceanographers. The Agulhas current's retroflection is now key to an understanding of its dynamics.

Retroflection regions The North Brazil Current (NBC) is a western boundary current that flows off the coast of northeast Brazil, in the tropical Atlantic that transports upper ocean waters across the equator. It retroflects between 4°N and 10°N. Particularly during summer and fall, the NBC retroflects from the coast at 6° to 7°N and feeds the North Equatorial Countercurrent and North Equatorial Undercurrent. The NBC sheds large anticyclonic rings that move northwestward along the continental break. (Didden and Schott, 1993). These warm rings could play an important role in the net meridional transport of warm water in the upper layers of the Atlantic Ocean as part of the meridional overturning circulation (MOC). 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. This water becomes the Agulhas Return Current, rejoining the Indian Ocean Gyre. It is estimated that up to 85 Sv (Sverdrups) 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.

References

Worked examples

Example 1 — a first encounter with Retroflect

Start with the simplest possible case. Write down what Retroflect 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 Retroflect 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 Retroflect 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 Retroflect

In research: Retroflect 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 Retroflect 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: Retroflect is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ocean currents, Oceans, so understanding it makes those chapters shorter.
In everyday life: Look for Retroflect 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 Retroflect in 20 minutes

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

Frequently asked questions

What is Retroflect in simple terms?

Retroflection is the movement of an ocean current that doubles back on itself. Usage history More commonly used to describe the way the mammalian intestine or uterus might turn back on itself, retroflection was first used in an oceanographic sense in 1970 by South African oceanographer Nils Bang, t…

Why does Retroflect 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 Retroflect?

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 Retroflect.