OCEANS IN MOTION
second part of chap. 1 16-31
OCEANS IN MOTION
waves , tides, and currents
The Oceans Store 1000x More Heat Than the Atmosphere
The Oceans Transport Heat Vertically and Horizontally, from Low Latitudes to High
Net radiative gain
Net
radiative
loss
Net
radiative
loss
Winds
wave breaking
tidal mixing
(breaking internal waves)
Surface
Currents
Deep
Flow
Ocean Waves
 Wave Impacts
Damage to Oil Industry in 2005
from Hurricanes Katrina and Rita
• Oil Platforms:
– 3050 of 4000 in direct path
– 113 Destroyed
– 53 Damaged
• Oil Pipelines:
– 457 Damaged, including
101 large diameter pipelines
• Oil / chemical spills:
–
–
–
–
1 barrel or greater: 146
50 barrels or greater: 37
1000 barrels or greater: 6
No significant coastal or
wildlife impacts noted
Thunder Horse – 59,500 tons
World’s Largest Oil Platform
USCG Photo from July 2005
after evacuation for Hurricane Dennis
Source: Minerals Management Service Press Release 1 May 06
 Wave Impacts
 Wind Waves
How high will the seas get?
•
•
•
•
Fetch – Over what area is the wind working?
Duration – How long has the wind been blowing?
Wind Speed – How fast is the wind blowing?
Fully Developed Sea
– This is as high as the waves will get for a given
fetch, duration, and wind speed
– Due to losses in breaking waves, sea spray, and
white caps, no further energy goes into wave
generation
 Wind Waves
From Seas to Swell
I. WAVES write this down
• A. Characteristics
• do not move much mass but are
propagated through the water,
• " notice how a floating object seems to
bob up and down as the wave passes by"
• see diagram of length, period and velocity
• primarily wind driven,
 Physical Traits
Wave Anatomy (draw this)
Wave Height: H
Water Depth: h (don’t confuse h and H)
 Physical Traits
Period – How much time between each crest?
Frequency – How many crests pass each second?
 Physical Traits
Particle Motion in
a Deep Water Wave
L
- At the surface, orbital diameter equals
the wave height H.
- Orbital diameter decreases with depth
- At a depth of L/2, motion is negligible
H
Animation from: Dan Russell, Ph.D.,
Associate Professor of Applied Physics
at Kettering University in Flint, MI
http://www.kettering.edu/~drussell/Demos/waves/wavemotion.html
http://www.kettering.edu/~drussell/Demos/waves-intro/waves-intro.html
Storm south of New Zealand on 9 July
2004 generates swell which propagates
to North America in 12 days
http://esamultimedia.esa.int//images/EarthObservation/2007-05-15_wave_tracking_2004/pacific_20040709_20040721.gif
Animation of
observed swell
generated by a
storm south of
New Zealand
on 9 July 2004
propagating
across the
Pacific Ocean.
Color depicts
the wavelength
of the waves
tracked by the
Envisat ASAR
Wave mode,
with red being
the longest.
Long period
swell reaches
Alaska 12 days
later.
A similar case
was observed in
1963 by Dr.
Walter Munk
and his
colleagues
during the
“Waves Across
the Pacific”
experiment.
Credits:
IFREMER BOOST
Technologies
 Mathematical Traits
Wave Interference
Two
progressive
waves
Animation from: Dan Russell, Ph.D.,
Associate Professor of Applied Physics at
Kettering University in Flint, MI
Two sinusoidal waves traveling in the same direction. The phase
difference between the waves varies with time, and the effects of
both constructive and destructive interference may be seen. The
net surface displacement is simply the sum of the individual wave
displacements.
 Rogue Waves
???
(unrealistic)
72 ft
 Rogue Waves
Simulation of wave encountered by the German cargo ship München,
lost at sea on 12 Dec 78. Wreckage indicated possibility of a 20m wave.
Rogue Waves
• 10-25m wave height
– Much larger than surrounding waves (more than twice the significant
wave height)
• Physics of wave formation is an area of active research
– Energy transfer from smaller waves to one or more large waves
– Wave-current interaction
– Wave superposition
• Appear to be more frequent than linear wave theory
statistics predict
– Recent study of satellite data: on any given day, 3 rogue waves exist
somewhere on earth
• Force of 100 metric tons per m2 is possible (much greater
than typical ship design strength of 15 t/m2)
• Myth: 200 ships lost over past 20 years due to rogues
 Rogue Waves
This rare photo of a rogue wave was taken by
first mate Philippe Lijour aboard the
supertanker Esso Languedoc, during a storm off
Durban in South Africa in 1980. The mast seen
starboard in the photo stands 25 metres above
mean sea level. The wave approached the ship
from behind before breaking over the deck, but
in this case caused only minor damage. The mean
wave height at the time was between 5-10 metres.
Rogue waves are most common in the Agulhas
current off the east coast of South Africa, with
numerous well documented cases of extreme
individual waves, including some striking
photographs of damaged ships. Here is shown
bow damage received by Norwegian tanker
Wilstar in 1974: the combination of pitch motion
and a steep incoming wave can cause excessive
local structural damage. One of the aims of rogue
wave research is to recommend changes in ship
design to make them less vulnerable in future.
Bay of
Fundy
• Approximately 270 km long and 31 km wide, avg depth is 60m
• Natural period is nearly resonant with the semidiurnal tide
• Tidal range is 16m in the Minas Basin, near the head of the bay
• By comparison, the tidal range along the nearby Atlantic coast of
Nova Scotia is only 1.5-2.5m.
B. Shape change (write this)
• 1. as wave approaches shore there is a
shape change fig. 1-13
• If depth is less than 1/2 wavelength, the
wave crest will BREAK on shore
• 2. Wave character, force, are determined
by shore line composition, seasons and
substrate.
• (Bays, estuaries, rocky shore and sandy
beach) all experience different types of
waves
 Wave Shoaling
Types of Breakers
Tidal Modulation of Surf Zone
For a given wave height, bottom depth determines where the waves break.
For a given wave steepness, bottom slope determines how they break.
C. Types
•
add drawing
1. spilling breaker- gently sloping
bottom
•
2. plunging breaker- steeply sloping
bottom
•
3. surging breaker- no break because
of depth
 Wave Shoaling
Spilling breakers distribute their energy across a broad surf zone
 Wave Shoaling
Steep, plunging breakers are the archetypical breaker.
From photo by Jeff Devine.
Surfing 100 Miles Offshore
35 mph
Cortes
Bank
60 ft
http://video.google.com/videoplay?docid=1041053573910778617&q=surfing
 Wave Shoaling
favorable
swell
direction
San Clemente Island
Cortes Bank
Elevation in Meters
D. Tsunamiseismic shock generated wave
caused by sea floor disturbance
(volcanoes, earthquake,
landslide) 500 mph. No effect in
the deep ocean but a
DRAMATIC effect on the shore.
100 ft. waves are possible
17 July 2006 Indonesian Tsunami:
9.0 Earthquake
26 Dec 2004
500+ Killed, 35,000 Displaced
Kalimantan
Sumatra
Jakarta
Java
7.7 Earthquake
17 July 2006
http://earthquake.usgs.gov/eqcenter/recenteqsww/
 Tsunamis
c = (gh)1/2
Since h / L < 1/20, it travels as
a shallow water wave!
 Tsunamis
Anatomy of a Shoaling Tsunami
 Tsunamis
Tsunami Damage is Related to the
Slope of the Coastal Sea Floor
http://www.washingtonpost.com/wp-dyn/articles/A54530-2005Jan6.html
 Tsunamis
26 December, 2004
http://www.meted.ucar.edu/marine/mod3_wlc_propdis/tsunami_Dec2004.htm
Crest of Tsunami Approaching on the Horizon
Hat Ray Lai Beach
Krabi, Thailand
26 December, 2004
At least 200 people were
killed in this area.
http://www.timesonline.co.uk/article/0,,18690-1423373,00.html
This family of Swedish tourists
survived the tsunami after
being washed ashore by the
surging waters. Karin Svard
clung to a palm tree and later
found her family on higher
ground.
 Tsunamis
Tsunami
Warning
Systems
http://nctr.pmel.noaa.gov/Dart/Jpg/DART-II_05x.swf
Wave Classification
Wind Waves
Physical Traits
Mathematical Traits
Rogue Waves
Seiches
Wave Shoaling
Tsunamis
Internal Waves
 Internal Waves
Particle Motions in Internal Waves
http://www.es.flinders.edu.au/~mattom/IntroOc/lecture10.html (Fig. 7)
Courtesy of
Matthias Tomczak
Yellow dots: Water particles in the middle of the water column move up and down, but do not
move horizontally, as the wave passes through.
Magenta dots at the bottom: Particles oscillate horizontally as the wave passes. At a given
location, particles at the top and bottom of the water column move in opposite directions.
Groups of magenta dots: Areas of convergence and divergence follow the wave.
Convergence occurs where the respective layer is thickest, while divergence occurs where the
layers are thinnest.
The Great Wave off Kanagawa
Katsushika Hokusai (1760-1849)