Three parcels of seawater compete to sink. Which one wins?

• Warm and fresh
• Warm and salty
• Cold and salty

What drives surface currents, and what drives the deep loop?

• Wind at the surface, density differences below
• Fish migration at the surface, tides at depth
• Waves at the surface, wind at depth

Surface currents stream in straight lines exactly downwind.

In a tank with no wind, salty water meets fresh water. What happens?

• Salty water sinks and slides underneath
• Fresh water dives below the salty layer
• Both layers freeze in place at once

What does the name thermohaline circulation tell you?

• It is paced by tides and waves together
• It is driven by heat and salt setting density
• It is stirred by wind over hot sand

The deep loop takes centuries per lap. What does that imply for climate?

• The deep ocean never affects climate
• Changes made now echo for generations
• Surface currents will halt within years

The ocean absorbs a pulse of extra heat today. When will the deep loop fully answer?

• By next week, as surface currents race
• Never, since heat cannot enter water
• Centuries from now, not this year

A student says gyres prove water ignores rotation and follows wind directly. What is wrong?

• Wind never touches the ocean surface
• Rotation steers the flow into closed gyres
• Gyres appear only in tanks, never in oceans