geology

Ocean Surface Water Salinity

For this lab, you will be making scientific observations and interpretations about ocean

surface water salinity after plotting the salinity of ocean surface water at given latitudes. I

recommend that you print the lab and plot the data on the graph. Then, use your lab to

answer questions on our online class site so that you can then get credit for the laboratory

exercise.

Part 1: Sea Water

Go to the following website: https://www.weather.gov/jetstream/seawater

Read the information provided about sea water and answer the following questions. You

will not have to click the “Next” button or read any other pages than the one that initially

comes up on the screen.

1. What are the two most common elements in sea water, after hydrogen and oxygen?

A. carbon and nitrogen B. sulfur and magnesium C. helium and iron D. sodium and chloride

2. The normal range of ocean salinity ranges between _______________.

A. 20-30 grams per liter B. 33-37 grams per liter C. 100-125 grams per liter D. 135-142 grams per liter

3. Which of the ocean basins is the saltiest?

A. Pacific B. Atlantic C. Indian D. Arctic E. Southern

4. Fresh water, such as rain or runoff going into the ocean helps _______________the

salinity of the surface water.

A. increase B. decrease

5. Fresh water, in the form of water vapor, moves from the ocean to the atmosphere

through evaporation, causing ___________ salinity.

A. lower B. higher

6. The saltiest ocean water is in ______________.

A. the Red Sea and in the Persian Gulf region B. the Gulf of California and in the Gulf of Mexico C. the Gulf of Alaska and the Sea of Cortez D. the Sea of Japan and the Gulf of Aden

Part 2: Graphing Surface Salinity vs. Latitude

The following table contains the average salinity at various latitudes in the Pacific and

Atlantic Oceans. Plot this data, creating salinity curves on the graph, one for the Pacific

Ocean and one for the Atlantic Ocean. Use a blue colored pencil to connect points for the

Pacific Ocean, and a red colored pencil to connect points for the Atlantic Ocean with

smooth curves. The graph you will produce will provide a general picture of surface

water salinity in the ocean. Answer the questions that follow.

Latitude Salinity of Pacific Ocean (‰) Salinity of Atlantic Ocean (‰)

60° N 31.0 33.0

50° N 32.5 33.7

40° N 33.2 34.8

30° N 34.2 36.7

20° N 34.2 36.8

10° N 34.4 36.0

0° N 34.3 35.0

10° S 35.2 35.9

20° S 35.6 36.7

30° S 35.7 36.2

40° S 35.0 35.3

50° S 34.4 34.3

60° S 34.0 33.9

30

31

32

33

34

35

36

37

38

39

40

60° N 50° N 40° N 30° N 20° N 10° N 0° N 10° S 20° S 30° S 40° S 50° S 60° S

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Latitude

Surface Salinity vs. Latitude

Pacific Ocean

Atlantic Ocean

7. Which latitudes in the Atlantic Ocean have the highest surface salinities?

A. 20 degrees to 30 degrees north and south latitudes B. 40 degrees to 50 degrees north and south latitudes C. 0 degrees to 10 degrees north and south latitudes D. 60 degrees to 90 degrees north and south latitudes

8. What are two factors that control the salinity of seawater?

A. time and topography B. rock type and time C. evaporation and precipitation D. topography and evaporation

9. Why is the salinity of the surface waters of the equatorial and subtropical regions

(about 30 degrees latitude) in the Atlantic ocean different?

A. Precipitation in the equatorial water would lower the salinity, while evaporation in the subtropical region would increase the salinity.

B. Precipitation in the equatorial water would increase the salinity, while evaporation in the subtropical region would decrease the salinity.

10. Does the Atlantic or Pacific Ocean have a higher average surface salinity?

A. Atlantic B. Pacific