Which usually reflects more sunlight: white sea ice or dark ocean water?

• Dark ocean water
• White sea ice
• Both reflect the same share

A scientist gently adds cold, salty liquid water to warmer, fresher water in a tank. The added water is denser. What will it tend to do?

• Sink beneath the less dense water.
• Float above the other water because cold means lighter.
• Stay on top because dissolved salt stops water moving.

Upwelling guarantees that phytoplankton can grow even when there is no sunlight.

In a model, sea ice reflects 70 of 100 parts of incoming sunlight. The rest is absorbed. How many parts are absorbed?

Sea ice forms, leaving most salt in the liquid water below it. What effect does that extra salt have on the water?

• The water becomes fresher and less dense.
• The water loses all its salt and turns into vapour.
• The water becomes saltier and denser.

How can deep water rising toward the Southern Ocean surface help phytoplankton grow?

• It carries dissolved nutrients needed for growth.
• It carries sunlight from the dark depths to the surface.
• It carries all the food phytoplankton need to eat.

Under the same incoming sunlight, white sea ice is replaced by dark ocean water. What happens to sunlight absorbed as heat by that surface?

• Less heat is absorbed because water reflects more.
• The same heat is absorbed because reflection is equal.
• More heat is absorbed because water reflects less.

Maria says, "Wind alone explains all ocean circulation." Which correction adds another process taught in the lesson?

• Ocean currents never move water between places.
• Density differences also help move ocean water.
• Only warm surface water can move around Earth.