1. Next Midterm Monday, May 18, 2009, 1:00
Here in Gilfillan Auditorium, closed book
Same format as Test 1
Bring #2 pencil
Study Guide NOW POSTED on class web site

2. Transformation of Wind-Driven Deep-water Waves (Figure 7-7a)

3. Transformation of Wind-Driven Shallow-water Waves (Figure 7-7b)

4. Photography by Clark Little

5. Photography by Clark Little

6. Photography by Clark Little

7. Photography by Clark Little

8. Photography by Clark Little

9. Photography by Clark Little

10. Photography by Clark Little

11. Photography by Clark Little

12. Photography by Clark Little

13. Tsunamis
Sudden shifting of the ocean floor due to earthquakes, volcanic eruptions, and submarine slumping.
open ocean: short heights, long wavelengths (>100 km), and long periods mph!!!
shallow water: their length shortens and their height increases dramatically.

14. Global Wave Propagation After 2004 Sumatra Event
Massive 9.3 EQ. 30-ft vertical displacement, 60-ft horizontal displacement. “This tsunami is the first for which there are high-quality worldwide tide-gauge measurements and for which there are multiple-satellite altimetry passes of tsunami wave height in the open ocean.” Combined with numerical model simulations to show global reach of initial event. Mid-ocean ridges help to guide the tsunami energy propagation, which means they were still super long wavelength and hence super deep.
Titov, V., A.B. Rabinovich, H.O. Mojfeld, R.E. Thomson, and F.I. Gonzalez, The global reach of the 26 December 2004 Sumatra tsunami, Science, 309 (5743), , 2005.

16. Oregon Coastal Atlas Tsunami Hazard Information http://www
Oregon Coastal Atlas Tsunami Hazard Information or

17. Figure 7-13a

18. Tsunami from slumping? North Carolina example
Driscoll et al., Geology, 28(5):

19. Back to Wind-Driven Scenarios: Storm Surges
extremely high water levels due to
Low pressure system - big storms
persistent onshore winds
rise in sea level

20. Hurricanes! (W. Atlantic) Cyclones! (W. Pacific)

21. Hurricane Katrina, Saturday, Aug 27, 2005
NASA Advanced Microwave Scanning Radar

22. L Hurricane Katrina, Sunday, Aug 28, 2005
Accumulation of water driven shoreward by storm winds:
Elevated sea level at shore L
Blue is 0.25 inches of rain per hour, green = 0.5, yellow = 1.0, red = 2.0
low atmospheric pressure
accumulation of water driven shoreward by storm winds
Water is deeper at the shore area, allowing waves to progress farther inland.
NASA PPT Radar, Visible Infrared Scanner, Tropical Microwave Imager
GOES satellite

23. New Orleans, Wednesday, Aug 31, 2005
ESRI.com

24. OSU Wave Tank

25. Back to 1998 El Niño “The Perfect Storm” Condition Black in Hawaii

26. Other Types of Progressive Waves
There is one other notable type of progressive waves.
Internal waves which occur underwater and move along pycnoclines.

27. Internal Waves
Slower speeds than surface waves because the density difference between water masses is less than between air and water.
They occur when water masses slip over one another.
They have very long periods and very large heights.

28. Figure 5-17

29. Standing Waves Seas, swell, and surf are progressive waves.
Standing waves (seiches)…
Oscillate back and forth about a node i.e., a fixed point.
Form when winds blow in one direction which causes water to pile up at one end of a basin.

30. Node = Fixed Point Antinode = maximum displacement (Figure 7-11)

31. Summary
Waves are disturbances that are generated on or beneath the sea surface. Progressive waves move along the sea surface.
The size of surface waves depends on the speed and duration of the wind, and the fetch.
Waves affect water to a depth equal to or less than one-half their wavelength.
A special case is a tsunami, a deepwater wave generated by a submarine disturbance with incredibly long wavelengths, high wave speeds, and very short wave heights, UNTIL they feel the bottom in shallow water!

32. Summary (Cont.)
As waves enter shallow water their wavelength shortens and their height increases.
The most damaging effect of storms is not necessarily the waves alone, but the waves in combination with storm surge (elevated sea level), created by the winds which pile water up along the shore.