Deep ocean currents: cold, salty water sinks

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   The global conveyor drawn on a world map. What does the word thermohaline refer to, by Ari's reading (NOAA)?

   • Temperature and salinity
   • Tides and the pull of the Moon
   • Wind and waves
   • Depth and pressure

2. Read this first

   Use this

   Wind arrows above, density arrows far below.

3. 2.

   What drives deep-ocean currents, by Bo's reading (NOAA)?

   • Tides
   • Strong surface winds blowing steadily across the open ocean
   • Rivers
   • Differences in density from temperature and salinity
4. 3.

   NOAA: winds drive currents in the upper 100 m. Where do the density-driven currents flow, by Kira's reading?

   • Just in the top 100 m
   • Thousands of meters below the surface
   • Near the surface, pushed along by the wind
   • Inside rivers
5. 4.

   Which water is densest and sinks, by Jun's reading (NOAA)?

   • Cold, fresh rainwater
   • Warm, salty water
   • Warm, fresh water
   • Cold, salty water

6. Use this

   Sea ice forming above saltier, sinking water.

7. 5.

   When sea ice forms, what happens to the salt, by Luz's reading (NOAA)?

   • It rises into the air
   • It turns into fresh water
   • It freezes into the ice
   • It is left behind, making nearby water saltier
8. 6.

   Why does water near forming sea ice sink, by Milo's reading (NOAA)?

   • It gets colder and saltier, so its density rises
   • It gets fresher and lighter
   • It warms up and expands
   • The wind pushes it down

9. Use this

   The global conveyor drawn on a world map.

10. 7.

    Where does the global conveyor belt start, by Noah's reading (NOAA)?

    • At the equator in the Pacific
    • Near the pole in the North Atlantic
    • At the mouth of a river
    • In the middle of the Indian Ocean
11. 8.

    Where is the conveyor recharged with more cold, dense water, by Pia's reading (NOAA)?

    • In the warm Indian Ocean
    • Around Antarctica
    • Off a tropical island
    • At the equator
12. 9.

    About how long does a cubic meter of water take to complete the conveyor, by Ren's reading (NOAA)?

    • About 1 million years
    • About 1 year
    • About 1,000 years
    • About 10 days
13. 10.

    A deep current moves 2 cm a second (example data). How far does it go in 1 hour, by Zee's math?

    • 2 m
    • 72 m
    • 120 cm
    • 7.2 km