Deep ocean currents: cold, salty water sinks

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Water samples (model data)

   Sample	Temperature	Salinity
   A	2 °C	35 g/kg
   B	2 °C	33 g/kg
   C	20 °C	35 g/kg
   D	20 °C	33 g/kg

2. 1.

   Using the sample table, which water would sink below the others, by Bo's reading?

   • A, the coldest and saltiest
   • B, cold and fresher
   • D, the warmest and freshest
   • C, warm and salty
3. 2.

   Using the sample table, which water would stay at the surface, by Esme's reading?

   • C, warm and salty
   • B, cold and fresher
   • A, cold and salty
   • D, warm and fresher
4. 3.

   Sea ice forming above saltier, sinking water. NOAA: where the conveyor starts, warm water from the Gulf Stream loses heat to the cold air. What happens to that water, by Jun's reading?

   • It cools, grows denser and sinks
   • It warms and rises
   • It freshens and floats
   • The wind pushes it to the bottom

5. Use this

   The global conveyor drawn on a world map.

6. 4.

   After sinking in the North Atlantic, which way does the deep water flow, by Kira's reading (NOAA)?

   • North, toward the Arctic
   • Straight up to the surface
   • East, across the Atlantic into a closed inland sea
   • South, past the equator, toward Antarctica
7. 5.

   NOAA: cold bottom water returns to the surface through mixing and wind-driven upwelling. Why must it come back up, by Milo's reading?

   • Deep water warms at the bottom and boils
   • Deep water evaporates
   • Surface water keeps sinking, so deep water rises to close the loop
   • Deep water stays below for good
9. 6.

   A deep current moves 3 cm a second (example data). How far does it go in one day, by Noah's math?

   • About 2.6 km
   • About 72 cm
   • About 26 km
   • About 260 m
10. 7.

    At about 2.6 km a day, about how far does that current go in a year, by Pia's math?

    Use the picture in question 6.

    • About 2.6 km
    • About 9,500 km
    • About 950 km
    • About 95 km
12. 8.

    NOAA: a loop takes about 1,000 years. If a parcel covers 60,000 km in that time (example), what is its average speed, by Ren's math?

    • About 60,000,000 km a year
    • About 6 km a year
    • About 60 km a day
    • About 60 km a year
13. 9.

    NOAA: wind and tidal currents move tens to hundreds of cm a second. How does a 3 cm/s deep current compare with a 100 cm/s surface current, by Tala's math?

    Use the picture in question 8.

    • The deep current is about 33 times faster
    • The surface current is 97 times faster
    • They are about equal
    • The surface current is about 33 times faster
14. 10.

    Wind arrows above, density arrows far below. Which of these currents is driven by density rather than wind, by Zee's reading (NOAA)?

    • The trade-wind drift pushed along near the equator
    • Coastal upwelling
    • Deep water flowing south from the North Atlantic
    • A western boundary current