The Effects of Upwelling and Downwelling

Name ______________________
Lab Grade ______/10
Date __________
Period _________
Lab # _____ - The Effects of Upwelling and Downwelling
Pre-lab:
1. Construct the “Model Ocean Basin”, Page 7
a. Cut along the dotted lines
b. Cut out the “Cut Out” parts of the model ocean basin
c. In the circle
i. W Arrows = Warm water, Color in RED
ii. C Arrows = Cold water, Color in BLUE
d. Use a pencil point to carefully, poke a small hole through the circle with the
cross
e. Place the model ocean basin over the circle, line up the two holes you made
f. Attach the two papers with a paper fastener
2. Read the background information
3. Label the diagrams below as upwelling or downwelling
4. Bring the lab and model to class
Background Information:
In some near-shore areas of the ocean, coastal orientation, prevailing winds, prevailing
winds and Earth’s rotation combine to influence vertical ocean circulation. In these regions,
the wind sometimes transports water in the upper 10 to 100 m (33 ft to 330 ft). This
process, called coastal upwelling, brings to the sunlit surface nutrient-rich water, spurring
biological productivity. At other times and places, the wind transports near-surface water
towards the coast, causing warm surface waters to pile up and sink. This process, called
coastal downwelling, thickens the layer of nutrient-deficient water, reducing productivity.
Upwelling and downwelling are also associated with broad-scale atmosphere-ocean
interactions (e.g. El Nino and La Nina) that can impact year-to-year variability in climate.
Diagram:
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Objective:
☺ Explain the causes of upwelling and downwelling
☺ Describe the influence of the prevailing wind and Coriolis effect on upwelling and
downwelling
☺ Explain how scientists use “ocean color” to monitor ocean productivity
☺ Describe how upwelling and downwelling enhance or suppress marine productivity
Materials: Model Ocean Basin and Internet Access
Time: 2 Periods
PART A – MODEL OCEAN DATA
Procedure:
1. Surface waters (set in motion by wind) are deflected due to the Coriolis effect. Move
the circle of the model ocean basin until there is an “N” in the Hemisphere cut out (N=
North) and the wind direction is to the North.
2. The near-surface flow of water is approximately _________° to the (right, left) of
the wind direction. This net flow, as you recall from an earlier investigation, is called
Ekman transport. Hint: When you are determining left or right, look down the arrow
as if you were standing and looking in the direction the wind is blowing.
3. Prediction - If the wind is blowing South in the Northern Hemisphere, then the
approximate angle of near-surface water flow is _________ to the (right, left) of
the wind direction.
4. Now move the circle to check. ________°, (Right, Left) in the Northern Hemisphere
5. Now focus on movement in the Southern Hemisphere. Move the wheel to view “S” in
the cut out
a. If the wind is blowing North, the angle is _________° to the (right, left)
between the wind and near-surface water.
b. If the wind is blowing South, the angle is _________° to the (right, left)
between the wind and near-surface water.
6. Near-surface water transported away form the coast tends to be replaced by cooler
water from below in a process called upwelling. Rotate the circle to a Southern
hemisphere position with the wind blowing from south to north. This combination will
produce upwelling along the land’s (eastern, western) coast. Enter this information in
the data table.
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7. Coastal upwelling of nutrient-rich water stimulates the growth of marine autotrophs
(e.g. phytoplankton) that support fisheries. Now rotate the underlay to determine
that in the on the west coast of Africa, upwelling and increased productivity will be
generated by a wind blowing from (south to north, north to south).
8. When the wind transports near-surface water towards a coast, the warm surface
layer thickens and sinks, decreasing marine productivity. This process is called
downwelling. Rotate the circle to a positioning the Northern Hemisphere showing the
wind blowing from south to north. This combination will produce downwelling along the
land’s (eastern, western) coast.
9. Along the coast of central and northern California, prevailing surface winds blow from
north to south in the summer and from south to north in the winter. The season when
cold coastal upwelling water cools the overlying air to saturation and produces
frequent fog is (summer, winter).
10. In the Northern hemisphere, air moves away from a high-pressure system blowing in a
(clockwise, counterclockwise) direction. In the Southern hemisphere, air moves away
from a high-pressure system blowing in a (clockwise, counterclockwise) direction.
11. Draw arrows to show the direction of wind movement from a high-pressure system in
the Southern hemisphere.
N
12. Along the eastern sides of the Southern Hemisphere’s subtropical high-pressure
systems, winds blow from (south to north, north to south).
13. The Southern hemisphere’s trade winds have a strong component blowing from south
to north. This causes upwelling, high marine productivity, and abundant fish harvests
along the (western, eastern) coasts of Africa and South America.
14. There are times when upwelling is suppressed. What would happen during these times
to marine productivity along the coasts of Africa and South America mentioned in the
above question?
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15. Rotate the wheel to try all 8 combinations of possible situations that lead to upwelling
or downwelling along a coast.
16. So far, the investigation has been limited to considering coasts of continents. Now
you will determine if upwelling or downwelling occurs in ocean basins.
17. Place the transparency over the globe viewing the Northern Hemisphere Side.
Locate the Northeast trade winds in the open Pacific Ocean. What is the direction of
the Ekman transport?
18. Place the transparency over the globe viewing the Southern Hemisphere Side. Locate
the Southeasterlies (winds) in the open Pacific Ocean. What is the direction of the
Ekman transport?
19. Based on average wind directions, is there a convergence or divergence of equatorial
waters in the open Pacific Ocean?
20. Based on average wind directions and the Ekman transport, does upwelling or
downwelling occur along the equatorial waters in the open Pacific Ocean?
21. Explain why?
22. To help explain your answer, draw a detailed diagram of wind and water directions
Equator
Depth
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Data:
Complete the table by deciding for each combination if there is upwelling or downwelling.
Northern Hemisphere
Deflected to the (right, left)
Winds West Coast East Coast
South to
North
North to
South
Southern Hemisphere
Deflected to the (right, left)
Winds West Coast East Coast
South to
North
North to
South
PART B – REAL TIME OCEAN DATA
23. Go to http://www.ametsoc.org/amsedu/DS-Ocean/home.html. Scroll down to
“Biological”, Click on “Ocean Color Productivity”.
24. View the locations in the data table. Record the area as experiencing high or low
biological productivity.
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Data:
Location
Coast of California
(Summer month)
Coast of California
(Winter month)
West Coast of Africa
(This month)
West Coast of South America
(This month)
Equatorial Pacific
(This month)
Biological
Productivity
High or Low
Vertical Movement of Water
Upwelling or Downwelling
Conclusion Questions: (Answer in complete sentences)
25. How does the Coriolis effect affect the direction of surface waters?
26. When viewing a map of ocean biological productivity, what color is evidence for
possible upwelling and what color is evidence of possible downwelling?
27. How does upwelling lead to increased biological productivity and how does downwelling
lead to decreased biological productivity?
This laboratory investigation was modified from
DataStreme Ocean Benchmark Investigation 9 A
Upwelling and Ocean Productivity
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