Ocean Circulation #1
Name_____________________________
1. Using the image at left as a guide,
explain how wind and Ekman Transport
creates the raised sea surface in the center
of the subtropical gyres.
2. To what depth is water involved
in Ekman Transport (often called the
Ekman Layer)? Is this depth very deep
compared to the depths of the oceans?
3. Use labeled arrows on the image above left to show the pressure gradient in the water
created by the Ekman Transport.
4. As water starts to move because of this pressure gradient, the Coriolis Force starts to
affect the moving particles of water. According to geostrophy, the water flow will be
balanced between Coriolis and the pressure gradient. Explain which way the water will
flow relative to the gyres in the northern and southern hemispheres, and why this occurs.
5. On the diagram above, please use arrows of different lengths to show the velocity of
geostrophic currents to the north, east, south, and west of the center of the gyre. What
information is provided that allows you to determine the location of the strongest
currrents?
A
E
B
C
D
6. The image above shows the sea surface height (SSH) relative to the gravitational level.
By looking at other maps and globes in the classroom, draw the following lines of
latitude on the map: 60˚S, 30˚S, 0˚, 30˚N, and 60˚N.
7. How does the location of the subtropical gyres relate to the location of the trade winds
and westerlies?
8. Look at the map above, and keep in mind that the pressure gradient creates the velocity of
geostrophic flow and the Coriolis Force influences the direction of geostrophic flow.
Using labeled arrows, please indicate the direction and relative velocity (fast, med, slow)
of flow at the following places, and indicate the name of the current:
Location -- draw arrows on the map at these places
The northeastern Pacific off-shore of southern California
The northeastern Pacific immediately south of the Aleutian Islands
The northwestern Pacific immediately offshore of Japan
The southeastern Pacific off-shore of Chile
In the northwestern Atlantic immediately offshore of Cape Hatteras
Location A
Location B
Location C
Location D
Location E
Name of Current
9. Which two or three of the currents in the previous question do you think are the fastest?
What is the rationale of your answer?
10. In the images above, can you see evidence for surface currents? If so, what is the
evidence?
July 2012
11. What do these images have to do
with each other? In other words, how does
the process shown on the right create the
sea surface height relationships shown on
the left?
12. Make a prediction. What sea surface temperatures (SSTs) and chlorophyll levels would
we expect to see off the coast of California in the summer time? Explain the rationale
behind your prediction.
That’s Chlorophyll on the left and sea surface temperature on the right.
13. What is chlorophyll telling us? Why is it important?
14. Why is the chlorophyll high and the temperature low along the coast of California?
Where is the high chlorophyll coming from? Where is the water with low temperatures
coming from?
15. The image to the right shows
that the upwelling is strongest
in the summer. Please use
labeled arrows to show
evidence of strong upwelling in
the summer. Tick marks are on
Jan 1 of each year.
16. Why is the upwelling strongest
in summer?