The Ocean Conveyor Moves Heat by Density

Lab Brief #2

🎯 Your mission

Predict it first. Then prove yourself right (or wrong).

⚡ The twist

Today's mountain was yesterday's ocean floor.

What you'll learn

Wind-driven surface currents carry warm water poleward, where it cools and, as sea ice forms and leaves its salt behind, grows saltier and denser until it sinks and returns at depth. This thermohaline circulation transports roughly as much heat as the atmosphere does, which is why north-west Europe sits several degrees warmer than other places at the same latitude. Meltwater dilutes the sinking limb, and that is the mechanism behind concern that the circulation could slow.

Key words

thermohaline circulation
The global ocean overturning driven by differences in temperature and salinity, which carry water down and back.
salinity
The salt content of seawater, which together with temperature sets its density and whether it sinks.

Make a hypothesis first

Guess: where will the water go first?

Say your guess out loud — then find out if you were right.

Get ready

🧰 What you need

clear tank
salt
food colouring
ice
warm water
thermometer

Get ready

⚠️ Safety first

Mop up spills straight away so nobody slips, and keep water away from sockets.

Step 1 of 4 · Read

Think about what you just learned: say what "thermohaline circulation" and "salinity" mean in your own words before you start.

Step 2 of 4 · Do

Layer warm fresh water, cold fresh water and cold salty water dyed different colours in a clear tank and record which sinks below which. Then add fresh meltwater to the densest layer and describe what happens to the sinking.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 3

Water in the thermohaline circulation sinks where it becomes:

How sure are you?😐 maybe

Question 2 of 3

North-west Europe is warmer than other places at its latitude because of:

How sure are you?😐 maybe

Question 3 of 3

Meltwater could slow the circulation because it makes the sinking water:

How sure are you?😐 maybe

Mind = blown

🌋 There are 1,500 active volcanoes on Earth right now.

Nice work!

You got 0 of 3 right.

Next: Feedbacks Set the Size of the Response All lessons

🎯

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✨ More to explore

🌍 Where you see this in real life: Today's weather, tomorrow's beach, next century's coastline — all this.

🏆 Stretch challenge (try it this week): Look at the sky for 5 minutes and try to predict tomorrow's weather.

👨‍👩‍👧 For the dinner table: “What's the slowest change you can think of?”

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The Ocean Conveyor Moves Heat by Density

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