Ocean Currents Motion in the Ocean | Lesson Plan

OCEAN CURRENTS LESSON PLAN

Motion in the Ocean

Theme
Ocean currents and waves

Links to Overview Essays and Resources Needed for Student

Research
http://oceanservice.noaa.gov/topics/navops/ports/
http://oceanservice.noaa.gov/education/kits/currents

Subject Area
Physical Science/Earth Science

Grade Level
9-12

Focus Question
What causes ocean currents and waves?

Learning Objectives
Students will identify the primary causes for ocean currents
and waves.
Students will explain how and why ocean currents vary with
increasing latitude.
Students will explain the cause of the Coriolis effect, and
how this effect influences ocean currents.
Students will calculate the magnitude of ocean currents,
given data from drifter studies.

Materials Needed
(Optional) Computers with internet access; if students do
not have access to the internet, download copies of materi-
als cited under Learning Procedure and provide copies of
these materials to each student or student group

Audio/Visual Materials Needed

None

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Motion in the Ocean | Lesson Plan Ocean Currents

Teaching Time
One 45-minute class period, plus time for student research

Seating Arrangement
Classroom style or groups of 3-4 students

Maximum Number of Students

30

Key Words
Ocean current
Ocean wave
Coriolis effect

Background Information
More than 98% of cargo shipped to and from the United States
is transported by water. In addition to accurate information
on the geography of coastal areas, safe and efficient naviga-
tion of coastal waters requires up-to-the minute information
on weather and sea conditions. Since these conditions can
vary significantly from place to place and can change dramati-
cally in a short period of time, mariners need accurate real-
time information to avoid groundings and collisions. NOAAs
Center for Operational Oceanographic Products and Services
(CO-OPS) collects and distributes oceanographic observations
and predictions to ensure safe, efficient and environmentally
sound maritime transportation. The Center:
provides information on water levels, coastal currents, and
tides;
establishes standards for collecting and processing these
data;
conducts research into new or improved oceanographic
observing systems;
designs software to improve data processing capabilities;
performs regular data analysis and quality control of data;
and
disseminates this information to the public.

CO-OPS also manages a national network of Physical

Oceanographic Real-Time Systems (PORTS) located in major
U.S. harbors. The PORTS network provides real-time infor-
mation such as water levels, currents, air gap (the clearance

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Ocean Currents Motion in the Ocean | Lesson Plan

between the water surface and the bottom of a bridge), weath-

er data, and other oceanographic information to help mariners
avoid groundings and collisions. Visit http://tidesandcurrents.
noaa.gov/products for more information on CO-OPS and their
data products. See http://tidesandcurrents.noaa.gov/programs for
more information on PORTS and other CO-OPS programs.

While CO-OPS deals mostly with currents along the coast and
inside estuaries, other NOAA Program Offices are involved
with measuring and understanding currents and circulation
patterns in the open ocean. NOAAs National Oceanographic
Data Center (NODC) compiles information from the latest
ocean current measurement programs that use current meters
and drifters. Through the NODC Web site (http://www.nodc.noaa.
gov/General/getdata.html/), you can access a variety of data sets
containing information on currents and other oceanographic
measurements, such as beach temperatures, coastal buoy data,
global temperature and salinity data, and photograph collec-
tions. For global current data obtained through satellite remote
sensing systems visit NOAAs Ocean Surface Current Analyses
- Real Time Web site at http://www.oscar.noaa.gov/.

In this lesson, students will explore the relationships between

currents, winds, and ocean waves.

Learning Procedure
1.
To prepare for this lesson, review the introductory information
on tides and currents at http://oceanservice.noaa.gov/topics/navops/
ports/ and http://oceanservice.noaa.gov/education/kits/currents, as well
as Parts I and II of the Currents Worksheets. If students will
not have access to the internet, makes enough copies of the
Currents Tutorial for each student or student group.

You may also want to review the Tides and Water Levels
Discovery Kit (http://oceanservice.noaa.gov/education/kits/tides/),
which offers a tutorial on the complex systems that govern the
movement of tides and water levels, a Roadmap to Resources
that directs you to specific tidal and current data, and lesson
plans for students in grades 912.

oceanservice.noaa.gov/education 
Motion in the Ocean | Lesson Plan Ocean Currents

2.
Ask students to comment on the present-day importance of
marine navigation. Students should realize that despite the
prevalence of air travel and advances in aerospace technology,
Earths oceans are still vital to freight transportation, energy
production, and recreation. Discuss the importance of real-time
information for safe navigation, and have students brainstorm
the types of information that would be useful to a present-day
mariner. Tell students that their assignment is to learn some
basic facts about ocean motion, and use this information to
solve problems dealing with winds, ocean waves, and cur-
rents.

3.
Provide a copy of the Currents Worksheets to each student or
student group, and have students use the online currents tuto-
rial (or printed copies) to answer worksheet questions.

4.
Lead a discussion of students answers to worksheet questions.
Be sure students understand the relationship between winds,
ocean waves, and currents.

The correct answers for Part I are:

(1) The velocity of currents includes speed and direction com-
ponents.

(2) Three factors that drive ocean currents are tidal motion,
wind, and differences in water temperature and salinity in
different parts of the ocean (thermohaline circulation).

(3) When a coastal tidal current floods, it moves toward the

land and away from the sea. When a coastal tidal current
ebbs, it moves toward the sea away from the land.

(4) As a coastal tidal current moves from ebbing to flooding

(and vice versa), there is a period during which there is no
current velocity. This period is called slack water.

(5) Tidal currents are most strongly influenced by motions of

the moon.

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Ocean Currents Motion in the Ocean | Lesson Plan

(6) When the moon is at full or new phases, the tidal current
velocities are strong and are called spring currents. When
the moon is at first or third quarter phases, tidal current
velocities are weak and are called neap currents.

(7) Perigean currents occur when the moon and Earth are clos-
est to each other. Apogean currents occur when the moon
and Earth are farthest from each other.

(8) Wave height is affected by wind speed, wind duration, and

fetch (the distance over water that the wind blows in a single
direction).

(9) Breaking waves are caused by friction between the seafloor

and the water.

(10) When a wave reaches a beach or coastline, it releases a burst

of energy that generates a current, which runs parallel to the
shoreline. This type of current is called a longshore current.

(11) Water flowing in a longshore current can transport beach

sediment and cause significant beach erosion through a
process known as longshore drift.

(12) A localized current that flows toward the ocean, perpen-

dicular or nearly perpendicular to the shoreline is called a
rip current.

(13) Swimmers caught in a rip current can escape by swim-

ming parallel to the shore instead of towards it, or by letting
the current carry them out to sea until the force weakens.

(14) A long offshore deposit of sand situated parallel to the

coast is called a barrier island.

(15) Upwelling occurs when winds blowing across the oceans

surface push water away from an area, causing subsurface
water to come up from beneath the surface to replace the
diverging surface water. Areas where this occurs are often
good for fishing, because subsurface water is typically rich
in nutrients, which support the growth of marine algae that
provide food for other species.

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Motion in the Ocean | Lesson Plan Ocean Currents

(16) Earths rotation causes air circulating in the atmosphere

to deflect toward the right in the Northern Hemisphere and
toward the left in the Southern Hemisphere. This deflection
is called the Coriolis effect.

(17) Between 5 degrees North latitude and about 25 degrees

North latitude, surface winds generally blow from the
northeast to the southwest, and are known as the trade
winds.

(18) Between 5 degrees North and 5 degrees South latitude,

where the winds are generally sporadic and have little or
no velocity. This region is called the doldrums.

(19) Between about 35 degrees North latitude and about 55

degrees North latitude, surface winds generally blow from
the west, and are known as westerlies.

(20) Global winds drag on the oceans surface, causing the water
to move in the direction that the wind is blowing and thus
create surface ocean currents. Deflection of these currents by
Earths rotation produces spiral currents called gyres.

(21) Each of the major ocean-wide gyres is flanked by a strong

and narrow western boundary current, and a weak and
broad eastern boundary current. The western boundary
current of the North Atlantic gyre is called the Gulf Stream,
and the eastern boundary current of this gyre is known as
the Canary Current.

(22) When surface water molecules move by the force of the

wind, friction with water molecules below them causes
movement of deeper water layers. Deeper layers move more
slowly than shallower layers, however, and all layers are
deflected by Earths rotation (to the right in the Northern
Hemisphere and to the left in the Southern Hemisphere).
These forces create a spiral effect called the Ekman spiral.

(23) Deep-ocean currents below 100 meters are driven by dif-

ferences in the waters density, in a process known as ther-
mohaline circulation.

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Ocean Currents Motion in the Ocean | Lesson Plan

(24) The global-scale system of deep-ocean currents is some-

times called the global conveyor belt.

(25) Global ocean circulation resulting from deep-ocean cur-

rents is vital to the worlds food chain because warm sur-
face waters that have been depleted of nutrients by biological
activity are enriched with these nutrients as they circulate as
deep- or bottom-water layers.

(26) Global ocean circulation resulting from deep-ocean cur-

rents could be disrupted by global warming if increased
rainfall in the North Atlantic and melting of glaciers and sea
ice reduced the sinking of cold, salty water.

(27) Ocean and coastal current velocities are typically are mea-
sured in knots, which is equal to about 1.15 standard (or
statute) miles per hour or about 1.85 kilometers per hour.

(28) Current measurements made with drifters are termed

Lagrangian measurements, while measurements of the
speed and direction of a fluid at a single point are termed
Eulerian measurements.

The correct answers for Part II are:

(1) 3 feet

(2) Increasing the wind speed by 60 knots would increase the

wave height to approximately 12 feet, while increasing the
fetch length by 60 nautical miles (nm) would increase the
wave height to less than 6 feet.

(3) A 60 knot wind would have to blow over a fetch of about

9 miles to produce a wave 10 feet high.

(4) The distance between the points is 524.6 nautical miles.

The total time elapsed is 6 days, 10.25 hours = 154.25
hours. So the estimated current speed is:

524.6 nm 154.25 hr = 3.40 nm/hr = 3.40 knots

The estimated direction of the current is northeast.

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Motion in the Ocean | Lesson Plan Ocean Currents

(5) The distance between the points is 1,443.68 kilometers =

1.444 x 108 centimeters. The total time elapsed is 14 days,
2.92 hours = 338.92 hours = 1.220 x 106 seconds. So the
estimated current speed is

1.444 x 108 cm 1.220 x 106 sec = 118.4 cm/sec

The estimated direction of the current is slightly east of

due south.

(6) Since the latitude at the equator is zero, the formula for
Coriolis acceleration suggests that the magnitude of this
acceleration at the equator is zero.

(7) The latitude of Tijuana is about 32.5 N. A velocity of 10

meters/second is equal to 1,000 centimeters/second. So, the
magnitude of the Coriolis acceleration is

(sin 32.5 1.5 x 10-4 1,000) cm/sec2

= 0.537 1.5 x 10-4 1,000 = 0.081 cm/sec2

The effect is very small.

(8) Even though the effect of Coriolis acceleration on soccer

balls, walking humans, etc. is practically negligible, when
it acts on very large masses over very long distances, the
acceleration becomes significant.

The Bridge Connection

http://www.vims.edu/bridge/ In the Site Navigation menu
on the left, click on Ocean Science Topics, then Physics,
then one of the headings at the top of the page for links and
resources about tides, waves, and currents.

The Me Connection
Have students write a short essay on how the Coriolis force
affects them personally, even though it only is significant at
very large scales.

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Ocean Currents Motion in the Ocean | Lesson Plan

Extensions
1. Visit the Tides and Water Levels Discovery Kit (http://
oceanservice.noaa.gov/education/kits/tides/) for additional
resources and lesson plans.

2. Visit http://www.usm.maine.edu/maps/lessons/nr10.htm and

http://www.usm.maine.edu/maps/lessons/nr11.htm for addi-
tional lesson plans and activities about currents from the
University of Southern Maines Osher Map Library.

3. Visit Multimedia Learning Objects at http://www.learn-

ingdemo.com/noaa/. Click on the links to Lessons 8 and 9
for interactive multimedia presentations and Learning
Activities on Ocean Currents and Ocean Waves, including
an activity involving landing safely on an aircraft carrier by
allowing for the Coriolis Effect.

Resources
http://oceanexplorer.noaa.gov/explorations/03edge/background/edu/
media/coriolis.pdf Lesson on the Coriolis force from
NOAAs Ocean Explorer program, including the Dishpan
Analogy explanation for this effect

http://oceanservice.noaa.gov/education/kits/tides/ NOAAs Tides

and Water Levels Discovery Kit

http://tidesandcurrents.noaa.gov NOAAs Center for Operational

Oceanographic Products and Services (CO-OPS) Web
page, with links to data and information about tides,
water levels, currents, predictions, weather observations,
forecasts, and harmonic constituents

http://www.usm.maine.edu/maps/lessons/nr10.htm and http://www.

usm.maine.edu/maps/lessons/nr11.htm Lesson plans and
activities about currents from the University of Southern
Maines Osher Map Library

http://www.eeb.ucla.edu/test/faculty/nezlin/PhysicalOceanography.htm
Online tutorial with additional details about ocean
currents

oceanservice.noaa.gov/education 
Ocean Currents and Waves | Lesson Plan Tides and Currents

National Science Education Standards

Content Standard A: Science as Inquiry
Abilities necessary to do scientific inquiry
Understandings about scientific inquiry

Content Standard B: Physical Science

Motions and forces

Content Standard D: Earth and Space Science

Energy in the Earth system

Content Standard E: Science and Technology

Abilities of technological design
Understandings about science and technology

Content Standard F: Science in Personal and Social

Perspectives
Natural resources
Environmental quality
Natural and human-induced hazards
Science and technology in local, national, and global chal-
lenges

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Ocean Currents Motion in the Ocean | Worksheet

TIDES AND CURRENTS WORKSHEET

Part I: Review Questions for Currents
Tutorial
(http://oceanservice.noaa.gov/education/kits/currents)

1. The __________ of currents includes speed and direction

components.

2. Three factors that drive ocean currents are __________.

3. When a coastal tidal current __________ it moves toward the

land and away from the sea. When a coastal tidal current
__________ it moves toward the sea away from the land.

4. As a coastal tidal current moves from ebbing to flooding

(and vice versa), there is a period during which there is no
current velocity. This period is called __________.

5. Tidal currents are most strongly influenced by motions of

the __________.

6. When the moon is at full or new phases, the tidal current

velocities are __________ and are called __________ When
the moon is at first or third quarter phases, tidal current
velocities are __________ and are called __________.

7. __________ currents occur when the moon and Earth are

closest to each other. __________ currents occur when the
moon and Earth are farthest from each other.

8. Wave height is affected by wind __________, wind ________,

and __________.

9. Breaking waves are caused by __________.

10. When a wave reaches a beach or coastline, it releases a

burst of energy that generates a current, which runs parallel
to the shoreline. This type of current is called a __________.

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Motion in the Ocean | Worksheet Ocean Currents

11. Water flowing in a longshore current can transport beach

sediment and cause significant beach erosion through a
process known as __________.

12. A localized current that flows toward the ocean, perpen-

dicular or nearly perpendicular to the shoreline is called a
__________.

13. Swimmers caught in a rip current can escape by ________.

14. A long offshore deposit of sand situated parallel to the

coast is called a __________ .

15. __________ occurs when winds blowing across the

oceans surface push water away from an area, causing
subsurface water to come up from beneath the surface to
replace the diverging surface water. Areas where this occurs
are often good for __________, because__________.

16. Earths rotation causes air circulating in the atmosphere

to deflect toward the right in the Northern Hemisphere and
toward the left in the Southern Hemisphere. This deflection
is called __________ .

17. Between 5 degrees North latitude and about 25 degrees

North latitude, surface winds generally blow from the
northeast to the southwest, and are known as the ________.

18. Between 5 degrees North and 5 degrees South latitude,

where the winds are generally sporadic and have little or
no velocity. This region is called __________.

19. Between about 35 degrees North latitude and about 55

degrees North latitude, surface winds generally blow from
the west, and are known as __________.

20. Global winds drag on the oceans surface, causing the

water to move in the direction that the wind is blowing
and thus create surface ocean currents. Deflection of these
currents by Earths rotation produces spiral currents called
__________ .

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Ocean Currents Motion in the Ocean | Worksheet

21. Each of the major ocean-wide gyres is flanked by a

strong and narrow western boundary current, and a weak
and broad eastern boundary current. The western bound-
ary current of the North Atlantic gyre is called __________,
and the eastern boundary current of this gyre is known as
__________.

22. When surface water molecules move by the force of the

wind, friction with water molecules below them causes
movement of deeper water layers. Deeper layers move more
slowly than shallower layers, however, and all layers are
deflected by Earths rotation (to the right in the Northern
Hemisphere and to the left in the Southern Hemisphere).
These forces create a spiral effect called __________.

23. Deep-ocean currents below 100 meters are driven by ____

______, in a process known as __________.

24. The global-scale system of deep-ocean currents is some-

times called the __________.

25. Global ocean circulation resulting from deep-ocean cur-

rents is vital to the worlds food chain because __________.

26. Global ocean circulation resulting from deep-ocean cur-

rents could be disrupted by global warming if__________.

27. Ocean and coastal current velocities are typically are

measured in __________, which is equal to about ________
standard (or statute) miles per hour or about __________
kilometers per hour.

28. Current measurements made with drifters are termed

__________ measurements, while measurements of the
speed and direction of a fluid at a single point are termed
__________ measurements.

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Motion in the Ocean | Worksheet Ocean Currents

Part II. Problems on Winds, Waves, and

Currents

1. Surface ocean waves are produced by winds. The height of

these waves depends upon wind speed, the length of time
the wind blows (duration) and the distance over which the
wind blows (fetch). In 1952, Charles Bretschneider created
a diagram that describes the relationship between these
parameters and provides an easy way to predict the height
of a wave produced by specific wind conditions. Figure
1 is an example of this kind of diagram (usually called a
Sverdrup-Munk-Bretschneider nomogram). The y-axis
describes Wind Speed; the x-axis describes Fetch Length;
solid curved lines in the middle of the diagram show the
Wave Height in feet (most Sverdrup-Munk-Bretschneider
nomograms also include lines showing wave period and
wind duration; these have been omitted from Figure 1 for
clarity). When using the nomogram, be sure to match these
lines with the correct labels!

Figure 1: Sverdrup-Munk-Bretschneider Nomogram

100
90
80
70 55
60 45
40
35
Wind Speed, knots

50 30
25
40 20
16
14
30 12
10
8
20 6
5
4
3

2
10
1 2 3 5 7 10 20 30 50 70 100 200 300 500700

Fetch Length, Nautical Miles

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Ocean Currents Motion in the Ocean | Worksheet

1. If a wind blows over a 10 nautical mile fetch at 21 knots,

what would the resulting wave height be?

2. What would cause the larger increase in wave height for

conditions in the preceding question: increasing the wind
speed by 60 knots or increasing the fetch length by 60 nau-
tical miles?

3. What would be the minimum fetch over which a 60 knot

wind would have to blow to produce a wave 10 feet high?

4. There are a variety of ways to measure the velocity of a

current. One of the oldest and simplest methods is to use a
drifter, which can be any floating object (an ideal drifter
is one that is not affected by wind; glass bottles partially
filled with sand are a traditional type of drifter). To mea-
sure current velocity, an observer places the drifter into
the water, measures the amount of time the drifter takes
to move a known distance, and notes the direction of the
drifters motion (since velocity is a vector quantity, and has
dimensions of direction as well as speed). Next, the observ-
er finds the speed of the current by dividing the distance
the drifter traveled by the time it took to travel that dis-
tance. The speed of the drifter combined with the direction
in which it moved is the currents velocity.

In early oceanographic studies, drifters were released into

the open ocean with an attached tag that asked any per-
son who recovered the drifter to return the tag along with
information about the date and location in which the drifter
was recovered. Some of these drifters were actually found
and their tags returned, providing the basis for estimates of
ocean currents.

Suppose a drifter is released near Charleston, SC from a

research vessel whose position is 322315 North latitude,
791233West longitude, at 0915 eastern standard time
(EST) on May 11, 2004. A sailing yacht recovers the drifter
at 1930 EST on May 17, 2004 in position 395623 North
latitude, 734435 West longitude. What is the estimated
velocity of the current that transported this drifter? In this
case, it is sufficient to describe the direction component

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Motion in the Ocean | Worksheet Ocean Currents

of the velocity vector as north, northeast, east, southeast,

south, southwest, west, or northwest. State the speed com-
ponent of the vector in knots (nautical miles per hour).
[Hint: You can use the calculator at http://www.wcrl.ars.usda.
gov/cec/java/lat-long.htm to find the distance between two
points whose latitude and longitude are known.]

If you would like to have a map of the area covered by the

drifter, visit the Marine Geoscience Data System Web site
(http://www.marine-geo.org/maps). Enter the latitude and lon-
gitude boundaries for the area you want the map to cover,
then click on the Map button. In this case you would
enter 40 as the northern boundary; -80 as the western
boundary (note that longitudes west of the prime meridian
are assigned a negative value, while longitudes east of the
prime meridian are positive); -73 as the eastern boundary;
and 32 as the southern boundary. The map will show the
elevation (or depth) of Earths surface in the included area.
You can download the map using the Save Image As . . .
function of your Web browser.

5. Suppose an amateur oceanographer in Oregon releases

a drift bottle from position 461356 North latitude,
1254712 West longitude, at 1140 Pacific standard time
(PST) on August 6, 2005. At 1435 PST on August 20, 2005,
the bottle is found floating between the islands of Santa
Cruz and Santa Rosa in Channel Islands National Park
at 340023 North latitude, 1200010 West longitude.
Estimate the velocity of the current that transported this
drifter. Describe the direction component of the velocity
vector as north, northeast, east, southeast, south, southwest,
west, or northwest, and state the speed component of the
vector in centimeters per second.

You can use the Marine Geoscience Data System Web

site (http://www.marine-geo.org/maps) to generate a map as
described above. Enter 47 as the northern boundary; -126
as the western boundary; -120 as the eastern boundary;
and 34 as the southern boundary.

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Ocean Currents Motion in the Ocean | Worksheet

6. The deflection of moving objects caused by Earths rotation

is called the Coriolis effect. Acceleration due to the Coriolis
effect always acts at right angles to the direction of the
velocity vector, and has a magnitude of

(2 w v sin f) cm/sec2

where w is the angular velocity of Earth, v is the velocity of

the moving object, and f is the latitude in degrees.

Since the angular velocity of Earth is about 7.29 x 10-5 radi-

ans/sec, acceleration due to the Coriolis effect is about

(1.5 x 10-4 v sin f) cm/sec2

(note that radians have no units).

What does this equation suggest about the magnitude of

the Coriolis acceleration at the equator?

7. Suppose a soccer player in Tijuana, Mexico kicks a soccer

ball with a velocity of 10 meters per second. What is the
effect of the Coriolis acceleration on the ball?

8. Given the results of the preceding question, why is

Coriolis acceleration significant to the circulation is the
atmosphere and ocean?

oceanservice.noaa.gov/education 17