earth science

Nansen bottle

Nansen bottle 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 Nansen bottle rather than just read about it. In short: A Nansen bottle is a device for obtaining samples of water at a specific depth. It was originally designed in 1894 by Fridtjof Nansen and further developed by Shale Niskin in 1966 and is more commonly known as a Niskin bottle.

Key takeaways

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

Reference excerpt

A Nansen bottle is a device for obtaining samples of water at a specific depth. It was originally designed in 1894 by Fridtjof Nansen and further developed by Shale Niskin in 1966 and is more commonly known as a Niskin bottle.

Description

The Nansen bottle (originally of brass) is designed for the capture of water deep in the ocean. It is essentially an open tube with a wide valve at each end connected together by a solid rod. A bottle is attached to the cable at its bottom using a clamping design and at its top by a tripping mechanism. A messenger weight is suspended below the clamping design. A heavily-weighted cable is lowered from a ship and multiple bottles are attached at calculated intervals in order to place them at specific depths. When the final bottle has been attached and lowered, the bottles are held at depth until the thermometers stabilize at temperature. A messenger weight is then sent down the cable to start a cascading triggering of the bottles. When the weight reaches the first bottle, the impact releases the tripping mechanism at the top, allowing the bottle to freely rotate from the bottom, ending in both valves closing, trapping the water sample inside. The messenger weight further impacts the bottom clamp, releasing the messenger weight suspended below it to travel to the next bottle in line. After all of the bottles are tripped, they are then retrieved by hauling in the cable. The sea temperature at the water sampling depth is recorded by means of a reversing thermometer fixed to the Nansen bottle. This is a mercury thermometer with a constriction in its capillary tube which, when the thermometer is inverted, causes the thread to break and trap the mercury, fixing the temperature reading. Since water pressure at depth will compress the thermometer walls and affect the indicated temperature, the thermometer is protected by a rigid enclosure. A non-protected thermometer is paired with the protected one, and comparison of the two temperature readings allows both temperature and pressure at the sampling point to be determined.

Niskin bottle

The Niskin bottle, patented by Shale Niskin in March 1966, is an improvement on the Nansen bottle. Instead of a metal bottle sealed at one end, the 'bottle' is a tube, usually plastic to minimize contamination of the sample, and open to the water at both ends. Each end is equipped with a cap which is either spring-loaded or tensioned by an elastic rope. The action of the messenger weight is to trip both caps to shut, sealing the tube. A reversing thermometer may also be carried on a frame fixed to the Niskin bottle. Since there is no rotation of the bottle to fix the temperature measurement, the thermometer has a separate spring-loaded rotating mechanism of its own tripped by the messenger weight.

A modern variation of the Niskin bottle uses actuated valves that may be either preset to trip at a specific depth detected by a pressure switch, or remotely controlled to do so via an electrical signal sent from the surface. This arrangement conveniently allows for a large number of Niskin bottles to be mounted together in a circular frame termed a rosette. As many as 36 bottles may be mounted on a single rosette. Thermistor temperature sensors are more commonly employed on Niskin bottle as they are more accurate than mercury thermometers.

References

External links Niskin Bottles Firing Underwater

Illustrations

Worked examples

Example 1 — a first encounter with Nansen bottle

Start with the simplest possible case. Write down what Nansen bottle 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 Nansen bottle 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 Nansen bottle 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 Nansen bottle

In research: Nansen bottle 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 Nansen bottle 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: Nansen bottle is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bottles, Fridtjof Nansen, Oceanographic instrumentation, so understanding it makes those chapters shorter.
In everyday life: Look for Nansen bottle 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 Nansen bottle in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Nansen bottle 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 Nansen bottle out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Nansen bottle in simple terms?

Why does Nansen bottle 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 Nansen bottle?

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 Nansen bottle.