Ocean Currents: Modeling the “Global
Conveyor Belt” in Your Kitchen
Abstract
Ocean currents have a profound effect on the climates of the continents, especially those
regions bordering on the ocean. The Gulf Stream makes northwest Europe much more
temperate than any other region at the same latitude, and the California Current keeps
Hawaii cooler than other land masses at the same latitude. In this project, you will model
the behavior of these "rivers" of hot and cold water within the ocean to find out how
temperature affects the currents' velocity.
Objective
The objective of this project is to make a model of ocean currents and measure how the
heat input affects velocity of the currents.
Introduction
Ocean currents profoundly affect the weather, marine transportation, and the cycling of
nutrients. Deep-ocean currents are driven by differences in the water's density. The
water's density is controlled by temperature (cold water is denser than warm water) and
salinity (salty water is denser than fresh water).
Deep-ocean currents are initiated in Earth's polar regions. Water flowing into the polar
regions becomes cold, which increases its density. As ice is formed when the water
freezes, freshwater is removed from the ocean (it has turned into ice), making the ocean
water saltier. The cold water is now denser, due to the added salts, thus it sinks toward
the ocean bottom. Surface water then moves in to replace the sinking water, thus creating
a current.
A global "conveyor belt" is set in motion when deep water forms in the North Atlantic,
sinks, moves south, and circulates around Antarctica, and then moves northward to the
Indian, Pacific, and Atlantic basins. It can take 1,000 years for water from the North
Atlantic to find its way into the North Pacific!
The global conveyor belt moves water slowly, 10 centimeters (cm) per second (sec) at
most, but it moves a lot of water. One hundred times the amount of water that is in the
Amazon River is transported by this huge, slow circulation pattern. The water moves
mainly because of differences in relative density, which you will explore in this project.
The goal of this project is to model ocean currents, with particular focus on the role of
heat in the currents' velocity.
Terms, Concepts, and Questions to Start Background Research
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Deep-ocean currents
Density
Salinity
Global conveyor belt
Velocity
Convection
Convection cell
Energy transfer
Materials and Equipment
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Glass bread loaf dish, 1.5-qt.
Thyme, dried (or any other dried leaf spice) (2 tsp.)
Teaspoon
Vegetable oil (about 4 cups)
Measuring cup
Spoon
Ceramic coffee mugs (2)
Small cans of Sterno® (4)
Lighter or matches
Thermometer
Ruler
Stopwatch
Funnel
Adult helper – REQUESTED PLEASE
Lab notebook (3-ring binder)
8 ½ x 11 paper
8 ½ x 11graph paper
Experimental Procedure – Be certain your lab notebook sections include the written
questions being asked.
1. Mix the vegetable oil and the thyme in the glass dish.
2. Stir thoroughly to distribute the flakes of thyme. The flakes of thyme will flow
with the liquid, showing the direction and velocity of any fluid flow.
3. Place the dish on top of the two ceramic mugs.
4. Observe the oil and spice mixture. With no heat (energy) being added to the
system, there should be little or no movement of the liquid, once it has settled.
5. Place a Sterno can underneath the dish, directly in the middle of the dish.
6. Light the Sterno can and let the liquid heat up for a couple of minutes. The
convection should start soon after the heat is applied.
7. As the oil heats and begins to flow, observe the pattern of fluid flow (circulation)
by noting the location of individual flakes of thyme over time. Write down all of
your observations (at least four observations) in your lab notebook. This is
your first labeled section(Observations) in your lab notebook.
a. This type of energy movement is called thermal convection, because
added heat causes the fluid flow (circulation by convection) by lowering
the density of the liquid.
8. Be sure to view the model several times during the experiment, both from above
the dish and from the side of the dish.
9. Draw a sketch of the model in your lab notebook. This is your second labeled
section(Model Sketch) in your lab notebook.
10. Draw a sketch of the circulation. Note the shape of the convection cell(s) or
moving bodies of liquid. This is your third labeled section(Circulation
Sketch) in your lab notebook.
11. Is the pattern approximately symmetric on the two sides of the heated area?
Where do you observe upward flow? Where do you see downward flow? Where
do you observe horizontal flow? Answer these questions in the Circulation
Sketch section above.
12. Measure the temperature of the oil in different parts of the model. Record these
temperatures in your lab notebook. This is the fourth labeled section(Oil
Temperatures) in your notebook.
a. What is the biggest temperature difference you can find? Answer in the
Oil Temperatures section above.
13. Measure the horizontal velocity of the convective flow near the surface of the
liquid.
a. Use the ruler (oriented lengthwise) to measure distance.
b. Use a stopwatch to measure the time it take a single flake to move a
certain distance.
c. Divide the distance by the time to get velocity (in centimeters per second).
d. For example, if the flake moves 3 cm in 5 secs, its velocity is .60 cm/sec.
14. Make another sketch of the model with arrows showing the direction and velocity
of the current. #13 and #14 are to be included in this fifth labeled
section(Velocities I) in your lab notebook.
15. Measure the velocity of the flakes in different parts of the model. Record these
velocities in your lab notebook. This is the sixth labeled section(Velocities II) in
your lab notebook. Also, answer the following questions in the same section.
a. Are all of the measurements approximately the same? Where are the
velocities the greatest? Where are they the smallest? What could explain
these variations in velocity? Are the directions of flow "away from" the
heated central area of the container? What effects or characteristics of the
model might cause variability in the velocities?
16. Add another Sterno can and measure the temperature of the oil and the velocity of
the flakes now. How does increasing the heat affect the velocity? This is the
seventh labeled section(Velocities III) in your lab notebook.
17. Add a third and fourth Sterno can, individually, and repeat your measurements of
temperature and velocity. Record these results in the eighth and ninth labeled
sections(Velocities IV and V) in your lab notebook.
18. Make a graph of the different temperatures of the oil versus the velocities of the
current. This is your tenth and final labeled section(Graphs) in your lab
notebook.
19. EXTRA CREDIT SECTION(this should take place after #17 and be labeled
as Cooler Temperature): Place a baggie of ice at one end of the dish (remove
Sterno) and allow several minutes for cooling and note any changes in circulation
flow and/or velocities. Measure the oil temperature, sketch the circulation changes
noted and note any changes in velocity. Add this temperature and velocity to your
graph in #18.
THE LAB NOTEBOOK WILL BE GRADED ON CONTENT AND NEATNESS.
IT IS DUE NO LATER THAN MAY 23, 2012. NO LATE PROJECTS WILL BE
ACCEPTED!!