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 stay at the surface, by Esme's reading?

   • D, warm and fresher
   • A, cold and salty
   • B, cold and fresher
   • C, warm and salty
3. 2.

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

4. Use this

   The global conveyor drawn on a world map.

5. 3.

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

   • Straight up to the surface
   • North, toward the Arctic
   • East, across the Atlantic into a closed inland sea
   • South, past the equator, toward Antarctica
6. 4.

   Where do branches of the conveyor rise back toward the surface, by Luz's reading (NOAA)?

   • They stay deep for good
   • Near the poles, where they cool
   • At the conveyor's North Atlantic start, where they cool
   • In the Indian and Pacific Oceans, as they warm
8. 5.

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

   • About 72 cm
   • About 260 m
   • About 2.6 km
   • About 26 km
9. 6.

   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 5.

   • About 950 km
   • About 95 km
   • About 2.6 km
   • About 9,500 km
11. 7.

    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 year
    • About 60 km a day
12. 8.

    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 7.

    • The surface current is about 33 times faster
    • The deep current is about 33 times faster
    • They are about equal
    • The surface current is 97 times faster
13. 9.

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

    • Deep water flowing south from the North Atlantic
    • Coastal upwelling
    • The trade-wind drift pushed along near the equator
    • A western boundary current
14. 10.

    The global conveyor drawn on a world map. NOAA: warm surface waters are low in nutrients, and deep water in the conveyor is enriched again. Why are upwelling zones rich in algae, by Ari's reading?

    • Sinking water carries algae down
    • Sea ice adds nutrients as it forms
    • Warm surface water holds the most nutrients
    • Rising deep water brings nutrients back to the sunlit surface