OCEANS IN MOTION second part of chap. 1 16-31

waves , tides, and currents 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 Surface Currents tidal mixing (breaking internal waves) Deep Flow

Ocean Waves

Damage to Oil Industry in 2005 from Hurricanes Katrina and Rita 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 Source: http://www.breitbart.com/news/2005/10/04/051004193044.krohifb6.html http://skytruth.mediatools.org/objects/view.acs?object_id=7230 http://www.mms.gov/ooc/press/2006/press0501.htm 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 Knowledge of wind and wave conditions is crucial to the success of Naval operations at sea. Rough seas affect the performance of personnel, sensors, weapon systems, and speed of advance. Ship design and crew training must account for operations in a wide range of wave conditions RAST = Recovery, Assist, Secure, Traverse Surf zone forecasts reduce uncertainty in conducting amphibious and special operations

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,

Wave Anatomy (draw this) Physical Traits Wave Anatomy (draw this) Wave Height: H Water Depth: h (don’t confuse h and H)

Wave Vocabulary Wave Height (H): overall vertical change in height between the wave crest (or peak) and the wave trough. Equal to twice the amplitude (a). Wavelength (L): the distance between two successive peaks or successive troughs. Steepness: (H/L) wave height divided by wave length. Period (T): the time interval between two successive peaks or successive troughs passing a fixed point; measured in seconds. Frequency (f): the number of peaks or the number of troughs which pass a fixed point per second.

Period – How much time between each crest? Physical Traits Period – How much time between each crest? Frequency – How many crests pass each second?

Particle Motion in a Deep Water Wave Physical Traits Particle Motion in a Deep Water Wave - At the surface, orbital diameter equals the wave height H. - Orbital diameter decreases with depth - At a depth of L/2, motion is negligible L 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

Long period swell reaches Alaska 12 days later. 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 http://esamultimedia.esa.int//images/EarthObservation/2007-05-15_wave_tracking_2004/pacific_20040709_20040721.gif

Animation from: Dan Russell, Ph.D., 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 72 ft (unrealistic) The giant wave depicted in The Perfect Storm was unrealistic. Considering the length of the Andrea Gail (72 ft), the wave depicted in the movie would have been approximately 200 ft high, far higher than any ever observed.

Rogue Waves The world's oceans claim on average one ship a week, often in mysterious circumstances. With little evidence to go on, investigators usually point at human error or poor maintenance but an alarming series of disappearances and near-sinkings, including world-class vessels with unblemished track records, has prompted the search for a more sinister cause and renewed belief in a maritime myth: the wall of water. Waves the height of an office block. Waves twice as large as any that ships are designed to ride over. These are not tsunamis or tidal waves, but huge breaking walls of water that come out of the blue. Suspicions these were fact not fiction were roused in 1978, by the cargo ship München. She was a state-of-the-art cargo ship. The December storms predicted when she set out to cross the Atlantic did not concern her German crew. The voyage was perfectly routine until at 3am on 12 December she sent out a garbled mayday message from the mid-Atlantic. Rescue attempts began immediately with over a hundred ships combing the ocean. The ship was never found. She went down with all 27 hands. An exhaustive search found just a few bits of wreckage, including an unlaunched lifeboat that bore a vital clue. It had been stowed 20m above the water line yet one of its attachment pins had twisted as though hit by an extreme force. The Maritime Court concluded that bad weather had caused an unusual event. Other seafarers could not help but consider the possibility of a mythical freak wave. Currently the biggest wave factored into most ship design is smooth, undulating and 15m high. A freak wave is not only far bigger, it is so steep it is almost breaking. This near-vertical wall of water is almost impossible to ride over - the wave just breaks over the ship. According to accident investigator, Rod Rainey, such a wave would exert a pressure of 100 tonnes per square metre on a ship, far greater than the 15 tonnes that ships are designed to withstand without damage. It's no wonder that even ships the size of the huge freighter München can sink without trace. 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 12 m wave: 6 metric tons per square meter Ship design: 15 t/m^2 Rogue wave: 100 t/m^2 1 metric ton / m^2 = 9.8 kPa

Rogue Waves 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. 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.

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 slope, seasons and substrate composition. (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.

Cortes Bank Surfing 100 Miles Offshore 35 mph 60 ft http://video.google.com/videoplay?docid=1041053573910778617&q=surfing

Wave Shoaling favorable swell direction San Clemente Island Cortes Bank Elevation in Meters

Wave set up contributes to formation of rip currents

RIP

D. Tsunami- 100 ft. waves are possible seismic 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: 500+ Killed, 35,000 Displaced 9.0 Earthquake 26 Dec 2004 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!

Anatomy of a Shoaling Tsunami Tsunamis Anatomy of a Shoaling Tsunami

Tsunami Damage is Related to the Slope of the Coastal Sea Floor 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

At least 200 people were killed in this area. 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.

Tsunami Warning Systems 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

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)