FINAL STUDY GUIDE
GEOL 1080 • INTRODUCTION TO OCEANOGRAPHY - FALL 2008
The fine print: this outline is not meant to be fully comprehensive. This lists all the major topics we discussed in class, but it
does not completely cover everything involved with every topic, so use this as a guide to your notes, and to what to look
at in the text.
The final is comprehensive but will emphasize the material we’ve covered since the third midterm. We’ve covered
thermohaline circulation, ENSO, waves and tides since the third midterm; these new topics are covered by this study
guide; use the midterm study guides to help you prepare for the older material that will be on the final.
Insurance is not available for the final, but that doesn’t mean you shouldn’t do the homework. In fact, its probably all the
more reason to do the homework and arrived prepared to score well on the exam.
The final exam will be held in PS102 at the UVU-scheduled time, which is available via www.uvu.edu.
Please do not be late. I will collect all finals when the last person who arrived on time is finished, or after 1:55 minutes of
time, which ever comes first.
1. OCEAN CIRCULATION Chapter 7. (note that only thermohaline circulation and ENSO will be emphasized as new material on
the final; surface currents will be covered to a lesser extent along with the rest of the material you’ve already been tested
on).
a. They fundamentally are driven by temperature differences (via winds in the case of surface currents); they transport heat
from the equator to the poles. 2/3 of transfer is done by winds (with latent heat of water) and about 1/3 by the currents.
i. Surface currents. These are horizontal movements that occur in the pycnocline They mimic the major wind belts.
ii. Deep ocean currents. These are driven by density differences. These currents keep the deep ocean very well mixed
b. Ocean exploration: The Fram and the Jeanette (captained by DeLong). Know the basics of these explorations and what
we learned scientifically from them (see box 7-2 p. 206).
c. Global pattern of surface currents.
i. Driven by winds, for the most part. But continents get in the way, and Coriolis effect plays a role.
ii. Ekman Spiral. Understand this and be able to draw it. See the text.
iii. Subtropical Gyres.
1) Driven by tradewinds and prevailing westerlies, combined with continents getting in the way and Coriolis effect.
2) There are 5 – N. & S Atlantic, N & S Pacific, Indian
3) Have component currents
a) Equatorial currents.
b) Western Boundary Currents. Strong currents due to western intensification.
i) Gulf Stream
(1) A major warm, western boundary current
(2) Know the major details of this current – location, size, speed, impacts, eddies, etc.
c) Prevailing westerlies and Coriolis bend western boundary currents towards east. I called these ‘return
currents’ in lecture. North Atlantic current, North Pacific current, west wind drift.
d) Eastern Boundary Currents: These are cold currents. California current. These are much more diffuse
currents than western boundary currents.
4) Eastern Counter Currents along equator – not part of the gyres
iv. Geostrophic Currents & Gyres
1) The Coriolis Effect causes water to curve towards the centers of the gyres, so that water is up to 2 m higher in
gyre center. Gravity causes water to flow downhill away from the gyre center. The coriolis effect and gravity
balance. The actual path of the water that results is the Geostrophic current.
v. Upwelling & downwelling. (in association with surface currents and winds)
1) Very important to life – upwelling brings nutrients to the surface.
2) Caused by convergence or divergence of currents – know where.
3) coastal effects – water moving towards coast causes downwelling, and vice versa. Gyre movements and coriolis
effect can create upwelling. Where is this important?
4) Upwelling & downwelling happen most easily at high latitudes where there is little variation in water
temperature and density with depth.
vi. Antarctic (Southern Ocean) currents
1) No continents blocking east-west flow
2) east wind drift, west wind drift or Antarctic Circumpolar Gyre, zones of convergence, divergence, and
abundant marine life from upwelling and current mixing
vii. El Nino/Southern Oscillation (ENSO)
1) Usual conditions
a) Southeast tradewinds drive southern equatorial current from east to west;
b) High pressure exists near 30oS, coast of S. America, drives tradewinds.
c) carries cool eastern boundary current (Peru current) waters to west.
GEOL 1080, Introduction to Oceanography, Final Study Guide, Prof. Bunds
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d) Water warms as it flows along the equator; water is warm at equator in western pacific (but cold in eastern
pacific)
e) Peru current, westward Eq. Current creates upwelling along S. American coast (productive fisheries based
on phytoplankton, anchovies).
2) ENSO conditions
a) High pressure fails; Tradewinds fail – can even reverse; Southern equatorial current fails; water along the
equator and off Peru warms by solar heating, and warm water in western pacific even migrates to east
b) Waters along S. American coast warm markedly – up to 9oC!!
c) Upwelling shuts off, fisheries crater.
d) Eastward water flow usually starts in fall, reaches eastern pacific midwinter
3) Recent large ENSO events were 1982 – 1983 and1997 – 1998 (1/1/82 to 12/23/83 & 1/1/97 to 3/10/98 roughly).
82-83 was strongest on record.
4) La Nina is the opposite
a) Strong SE Tradewinds
b) Generally reverse local effects
d. Deep Ocean Currents (Thermohaline circulation)
i. Driven by sinking of high density water at high latitudes
1) At high latitudes water at all depths is cold
2) Cold surface water salinity increases when sea ice forms, which removes nearly pure water; recall how water
density varies with temperature and salinity.
3) Flow rates are about 10 to 20 km per year. Very slow – but steady!
ii. Antarctic Bottom Water.
1) Densest water in oceans; forms under ice in Antarctica.
2) Flows north along bottoms of Atlantic, Pacific and Indian Oceans
3) Flows along western margins of oceans due to Coriolis Effect
4) Encircles Antarctica
iii. Antarctic Intermediate Water
iv. North Atlantic Deep Water.
1) Forms in Norwegian sea and off Greenland/Labrador,
2) Sinks and flows south in Atlantic Ocean.
3) Not as dense as Antarctic Bottom water, so flows over the top.
4) Flows along western margins of oceans due to Coriolis Effect
v. Global patterns of deep water currents
1) Sinking bottom waters must displace waters elsewhere. Part of Earth’s heat transfer system.
2. WAVES! (Chapter 8) [we may not get to Chapter 8 before the exam, in which case you won’t be responsible for this material
until the final exam]
a. A wave disturbance that travels and carries energy with it. Something must create the disturbance, and a force must act to
restore the system to its original state.
i. In ‘normal’ ocean waves, we are talking about a disturbance in the height of the water (often caused by wind), or
more exactly the height of the water-air interface. The restoring force is gravity (for all but very small capillary
water waves).
ii. What causes waves in the ocean?
1) Wind, currents (can cause internal waves), earthquakes, volcanic eruptions, landslides, humans. Wind is most
important.
b. Three types of matter waves that involve particle oscillations.
i. Pressure waves.
1) Movement is parallel to wave propagation direction. Speaker woofer and sound
ii. Shear waves
1) Particle movement is perpendicular to wave propagation direction. Guitar string.
iii. Surface waves - These are typical ocean waves.
1) Occur at interface between to materials with different mechanical properties – e.g., air and water; rock and air;
two masses of water (or air) with markedly different densities.
2) Circular particle movement.
3) Also can occur along the pycnocline.
4) We will be talking about these.
5) Know the geometric details: Crest and trough, Wavelength = L, Waveheight (amplitude) (trough to crest) = H,
Wave speed = S, Period – time between passing of adjacent crests; T = L/S, frequency (f = 1/T = S/L),
steepness = H/L,
6) if steepness exceeds 1/7, a wave will break (collapse) – in open water or at a shore
7) Relationship of wavelength to speed (and thus to period).
GEOL 1080, Introduction to Oceanography, Final Study Guide, Prof. Bunds
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i) Longer wavelength surface waves travel faster
ii) L = 1.56 m/s * T2
iii) The above translates to: S = sqrt(1.56*L)
iv) 10 m/s = 36,000 m/hr = 36 km/hr ~ 22 mph
8) Wave base
a) Circular motion decreases with distance downwards; at depth of L/2, motion is virtually zero – this is the
wave base.
b) Deep, transitional and Shallow water waves; know what these are and examples
iv. Generation of waves by wind
1) The size and energy of the waves that develop depend on:
a) Wind speed
b) Duration over which wind blows in a constant direction
c) Fetch – distance over which wind blows
d) Largest waves are in the Southern Ocean – strong winds, huge fetch.
2) Waveheight and to a lesser extent wavelength increase by wind action
3) If waveheight grows such that H/W > 1/7, a wave will break – whitecaps.
4) Once wave is travelling as fast as the wind, no further growth can occur
5) Sea and Swell
a) ‘Sea’ or sea area is the area where wind creates waves.
b) Fully developed sea is one in which waves are as big as the wind can make them – more fetch and duration
doesn’t produce bigger waves.
c) Swell – Uniform, smooth, sinusoidal waves. They are generated by storms, but occur far from them because
long wavelength waves in sea area travel faster than short wavelength waves and outrun them. Also, the
smooth, long wavelength swell waves travel very efficiently (with little energy loss). Thus, at a long
distance (up to thousands of miles) from a storm, swell waves occur.
c. Breaking of waves at coasts; why it occurs, plunging vs spilling waves
d. Physical properties of waves
i. Wave interference; constructive and destructive; rogue waves
ii. Wave reflection ocean waves can bounce off of solid surfaces just as light reflects off of a mirror.
iii. Wave refraction– bending towards areas where they move more slowly. (important to wave size, for example at
Jaws on Maui, erosion at coastlines)
e. Examples of wave processes
i. Jaws on Maui
1) Large swells originate at distant storms
2) Depth of lava flow/reef is correct to cause long wavelength, large swell waves break
3) Tongue – like shape of reef causes waves to refract and focuses their energy, creating larger waves
4) Deeper water area alongside reef does not cause waves to break and their energy is refracted away from this area
so there is a place for surfers to get back out into the water to surf the big waves
5) Large waves that break spectacularly at Jaws, such as we saw in ‘In God’s Hands’ are nearly 400 m in
wavelength. 400 m wavelength waves are fast – nearly 60 mph in the open ocean. That’s why the surfers need
to be towed into the waves by wave runners.
ii. The Wedge at Newport Beach, southern California (the wedge is nicely covered in the text)
1) Waves reflect off of jetty.
2) Reflected waves interfere constructively with storm swell waves across a narrow area, making a large wedgeshaped wave.
f. Tsunamis
i. Know the causes (most from earthquakes, some from landslides)
ii. Geometry (H, L, S, T)
iii. When they reach the coast
1) Generally not a giant breaking wave; rather, appears more as a strong flood or surge of water, like a very rapid,
very extreme tide (hence the misleading term ‘tidal wave’).
2) Either a crest or a trough can reach a particular spot on the coast first.
3) The period is minutes
a) T=L/S=200/700 = 17 minutes [probably a bit less at the coast, 10 to 15 minutes]
b) When a trough hits coast first, people can be tempted into investigating the sub-tidal areas that are exposed
(and where many fish can lie stranded); this has led to many deaths.
4) Shape of the coast is important – topic of chapter 10.
5) Speed of the advancing surge is a few to several (i.e., 4 m/s), which you can’t outrun. They slow a lot in
shallow coastal waters.
iv. Forecasting and the Pacific Tsunami Warning Center (PTWC).
GEOL 1080, Introduction to Oceanography, Final Study Guide, Prof. Bunds
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a) Possible to provide warnings of tsunamis to areas across the Pacific from initiation site
b) How much warning?
i) Example: EQ in Aleutian Islands.
ii) Hawaii is ~4500 km from the EQ.
iii) 4500km/(700km/hr) = 6.4 hr
c) Pacific is monitored for large EQ’s that could generate a tsunami
d) tide gauges near sites of large EQ’s are monitored for signs of tsunami
e) watches and warnings are issued. walk don’t run
f) How much warning?
i) Example: EQ in Aleutian Islands.
ii) Hawaii is ~4500 km from the EQ.
iii) 4500km/(700km/hr) = 6.4 hr
2) http://cwis.usc.edu/dept/tsunamis/
3. TIDES
a. Know what they are – relatively high and low regions of water; essentially very long wavelength waves
b. Moon (and Sun) cause 2 bulges to form one on the side of the Earth facing the Moon (and Sun), and on the far side of the
Earth
c. Understand why the Moon and Sun cause 2 bulges to form (Centripetal force and gravity)
d. Effect of the Sun: Because the Sun is so much farther away, it makes tidal bulges about 1/2 the size of the lunar bulges.
e. Daily tidal cycle – tides repeat every lunar day (24 hours and 50 minutes)
f. Diurnal, semidiurnal and mixed tides (see page 276 of your text).
g. Monthly tidal cycle – tidal pattern follows orbit of moon around Earth
i. Spring tides: occur during new and full moon, the bulges from the moon and sun overlap, giving constructive
interference and large tidal range (not named for the season!) [new moon occurs when Moon is on the same side
of Earth as the Sun; full moon occurs when the Moon is on the opposite side of Earth as the Sun]
ii. Neap tides: occur during first and third quarter moon, when the bulges created by the Sun and Moon are oppositely
aligned (at 90o), giving destructive interference and a small tidal range, called neap tides.
iii. Grunions! (see box 9-2 in your text – they are amazing little fish).
iv. You should be comfortable with the monthly tidal cycle, including the relation of new, full, 1st and 3rd quarter
moons to spring and neap tides, as well as what new, full, 1st and 3rd quarter moons look like and what time of day
they rise and set.
h. Effects of Bays on tides
i. effects of bays can produce large tides (e.g., Cook Inlet, Alaska, Bay of Fundy, Canada).
ii. Bay of Fundy
1) largest tidal range in the world, up to 17 m, (built off of a ‘natural’ range of 2m).
iii. Can get strong currents in bays, especially from retreating waters
iv. Tidal bores can occur (recall slides, web movie)
v. Damaging tides: are possible when everything is lined up (i.e., Sun and Moon), especially if a storm coincides with
unusually high tides
i. Tidal Bores – slow-moving or even standing (stationary) waves formed when a large incoming tide collides with the
outgoing tide and/or outflow from a river. These can be quite dramatic, possibly even dangerous and exotic surf
locations. We looked at a youtube video of people surfing an amazing tidal bore in the Amazon River basin.
Study Questions
If you want to turn these in, please be sure to answer them on separate sheets of paper and staple everything together! Note that if you
score below C- on the exam you can receive points equivalent to a C- by doing these questions AND the suggested problems from the back of
the appropriate chapters AND turning them all in before the end of the testing period. The suggested chapter problems are listed on the
syllabus (which you received in class and is available on the course website).
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What are the two main types of ocean currents, and what is the main driving force behind each?
What are the major atmospheric and oceanographic changes (e.g., pressure, movement, temperature, fisheries) along the
tropical Pacific that cause and result from ENSO. [Great additional ENSO info is available at http://www.noaa.gov].
What causes deep ocean circulation?
From where does the most dense water in the oceans come?
Do polar bears live near the north pole, the south pole, or both?
Do penguins live near the north pole, the south pole, or both?
Write the chemical reaction for a perfect burn of methane (this should be in your lecture notes).
Approximately how much CO2 is produced by burning 1 gallon of gasoline?
GEOL 1080, Introduction to Oceanography, Final Study Guide, Prof. Bunds
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To what extent have humans increased the amount of CO2 in the atmosphere?
Explain (carefully) how humans are influencing the Earth’s climate through the greenhouse effect.
Draw a picture of a surface wave on the ocean. Label all of its key components – wavelength, height, etc.
I saw an ocean wave that was 10 meters high and 30 meters in wavelength. Do you believe me? Why or why not?
How deep must a submarine go to escape the effects of large surface waves 30 meters in height and 250 meters in
wavelength?
If the waves that the submarine is diving to escape are traveling at a speed of 20 m/s, what is their period?
Is a wave with L = 100 meters that is in water 6 meters deep considered a deep, transitional or shallow water wave?
Compare the speed that a wave of wavelength 100 meters in the deep ocean, water that is 40 meters deep, and water that is 4
meters deep.
Discuss the primary factors that control the size of waves that are produced by wind.
Explain what a ‘fully developed sea’ is.
What is ‘swell?’
The large waves that people surf are generated by the wind of distant storms. How do the surfing waves that arrive at the
beach differ from the waves present in the storm area? Why do they differ so much?
What conditions lead to spilling and plunging breakers?
Using a sketch, explain the cause of unusually large waves at ‘The Wedge’ in Newport Beach, California.
Why do surfers use waverunners to catch especially large waves?
What is the difference between the height and the face or a wave?
Describe a tsunami in the open ocean (H,L,S, etc.).
What causes most tsunamis?
Explain how the Pacific Tsunami Warning Center decides to issue tsunami warnings and watches.
Hawaii is about 4500 km from the Aleutian Islands off of Alaska. Estimate how long it would take a tsunami to travel from
the Aleutians to Hawaii.
Describe what a tsunami might look like as it washes ashore.
The first sign of an incoming tsunami is not always a rise in water level (e.g., a wave peak arriving) – explain.
Approximately how long following an indication of an incoming tsunami, other than a wave peak, would you expect the
dangerous wave peak to arrive?
What are tides – describe what people see and measure as ‘tides.’
Tides repeat every 24 hours and 50 minutes. Explain why, using a sketch.
Explain why the Moon creates tidal bulges on both the side of Earth closest to it and the opposite side, using words and a
sketch. Be sure that at the very least you can sketch the Earth and moon and the tidal bulges that are created on Earth by its
interaction with the moon.
How often does the moon orbit the Earth?
Describe and explain the origin of spring tides, using words and a sketch of the earth-moon-sun system. Be sure to relate
spring tides to the phases of the moon
Describe and explain the origin of neap tides Be sure to relate neap tides to the phases of the moon.
Explain how Grunion use the tides in their reproductive process (see box 9-2 in your text)..
Where and how large is the largest tidal range in the world?
What is a tidal bore?
Explain what a semi-diurnal tidal pattern is, and give an example of a place that experiences them.
Explain what a diurnal tidal pattern is, and give an example of a place that experiences them.
Explain what a mixed tidal pattern is, and give an example of a place that experiences them.
Sketch a graph that shows the tides over a one month period in an area that experiences a mixed tidal pattern.
What is a flood tide? What is an ebb tide? What is slack water? In addition to using words to answer these questions, draw
and label a sketch that illustrates these ideas.
What is meant by tidal range, and what is a typical tidal range, for example in California?
GEOL 1080, Introduction to Oceanography, Final Study Guide, Prof. Bunds
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