1. Welcome to Geosc040, Apr 1; Lecture 20 Waves Pontoon Little Big town Thanks to Kierstin E. Waterfalls TLC Thanks to Rachel B. Swim Jack's Mannequin Thanks to Jenna Z.

2. Read Chapter 8!! Quiz 2 April 14. Homework 3 due today by 11pm On-line Assignment 10 due Apr 8 Extra Credit Letters accepted until April 4

3. Convention on International Trade in Endangered Species CITES Required reading on the course web site: Lecture Notes link

4. Chesapeake Bay “Report Card”

5. Nutrients that cause Eutrophication and, ultimately, Hypoxia include A.Nitrogen B.Calcium C.Phosphorous D.Gatorade E.(A) and (C)

6. Key Definitions Hypoxia-- development of low concentrations of dissolved oxygen. Primarily occurs near bottom and is deleterious to organisms (different organisms have different tolerances) Eutrophication-- an environmental nutrient excess. Occurs when algal production of organic matter exceeds that which can be respired without reducing available dissolved oxygen below dangerous levels

7. The vicious cycle (Example of Chesapeake Bay): 1.Excess nutrients supplied in rivers to the Bay support luxurious blooms of phytoplankton (microscopic plants) 2.sinking organic matter (that is, the phytoplankton, but sewage and sludge have the same net effect) is oxidized by bacteria, thereby consuming oxygen 3.oxygen deficits occur in bottom waters--these are harmful to benthic organisms, many of which have economic value 4.the nutrients released during respiration in deeper waters are cycled back to the surface and produce more blooms and further organic matter loading a lack of mixing (stratification) resulting from seasonally strong salinity and temperature gradients (surface to bottom) prohibits oxygenation of bottom waters. A Major Problem: Eutrophication

8. The Energy Cycle Note that photosynthesis (and formation of plant organic matter) requires sunlight and nutrients Organic matter is consumed by animals and plants (respiration), supporting their growth Nutrients must be “recycled” (excreted by animals, “regenerated” by bacteria) to be reused by plants Photosynthesis Consumers nutrients

9. Prolonged periods of dissolved oxygen below ~ 2 mg/L eliminate most “ seafood ” from the affected region Each organism has its own tolerance limits Values of dissolved oxygen at or above 5 mg/L are considered “ healthy ” During the summer, 30- 40 % of the volume of the Bay experiences values <5 mg/L A Major Problem: Hypoxia Dissolved Oxygen Concentrations

10. http://www.chesapeakebay.net/

11. Why are oxygen concentrations during times of eutrophication generally lowest in the upper Chesapeake Bay? A.This is where the water is deepest? B.This is where thermal stratification is weakest C.This is where nutrients enter the bay, from the Susquehanna and other rivers D.All of the above E.None of the above Upper Bay Lower Bay

12. Eutrophication A.Is a sign of a healthy ecosystem B.Results from an excess of solar energy C.Is accompanied by low surface-water productivity D.Results from an excess of nutrients E.All of the above

13. Which of the following typically cause(s) excess nutrient and pollutant flows to rivers, which then leads to Eutrophication and Hypoxia A.Excess fertilization of farm croplands A.Clearcut forest tracts A.Storm water runoff A.Automobile emissions A.All of the above

14. Waves! in the Ocean Nearly all waves in the ocean are produced by Wind What is a Wave?

15. DEFINITIONS SWL-- still water level H= wave height (distance from crest to trough) in meters L= wavelength in meters S= Wave speed (or celerity) in meters/sec T= wave period in seconds (time for one wavelength to pass) d= depth of water column in meters n= water surface displacement from SWL SWL L S Wave Definitions Daniel A. Russell, Graduate Program in Acoustics, PSU http://www.acs.psu.edu/drussell/Demos/waves-intro/waves-intro.html

16. DEFINITIONS SWL-- still water level H= wave height (distance from crest to trough) in meters L= wavelength in meters S= Wave speed (or celerity) in meters/sec T= wave period in seconds (time for one wavelength to pass) d= depth of water column in meters n= water surface displacement from SWL SWL L S Wave Definitions http://www.acs.psu.edu/drussell/Demos/waves-intro/waves-intro.html

17. DEFINITIONS SWL-- still water level H= wave height (distance from crest to trough) in meters L= wavelength in meters S= Wave speed (or celerity) in meters/sec T= wave period in seconds (time for one wavelength to pass) d= depth of water column in meters n= water surface displacement from SWL SWL L S Wave Definitions Wavelength L

18. S= Wave speed (or celerity) in meters/sec T= wave period in seconds (time for one wavelength to pass) http://www.acs.psu.edu/drussell/Demos/waves-intro/waves-intro.html DEFINITIONS SWL-- still water level H= wave height (distance from crest to trough) in meters L= wavelength in meters S= Wave speed (or celerity) in meters/sec T= wave period in seconds (time for one wavelength to pass) d= depth of water column in meters n= water surface displacement from SWL

19. S= Wave speed (or celerity) in meters/sec T= wave period in seconds (time for one wavelength to pass) d= depth of water column in meters

20. S= Wave speed (or celerity) in meters/sec T= wave period in seconds (time for one wavelength to pass) d= depth of water column in meters

21. Deep water wave vs. Shallow water waves

22. Waves behave differently depending on the relationship between water depth and wavelength Types of Waves Defined in terms of Water Depth Deep water wave: d >> L and Shallow water wave: d ≤ L

23. Waves behave differently depending on the relationship between water depth and wavelength Types of Waves Defined in terms of Water Depth Wave behavior differs when d >> L (Deep water wave) and d ≤ L (Shallow water wave) that is, when water depth d is much greater than wavelength L versus when d and L are roughly equal. By definition a wave is a ”deep-water wave” when d > L/2, or a ”shallow-water wave” when d < L/20

24. Types of Waves Defined in terms of Water Depth Only some of the molecules in the water column are involved in a deep-water wave…

25. Wavelength is the distance between wave crests L S SWL A B C Which of these waves has the shortest wavelength? (wavelength is the distance between wavecrests) A B C

26. Speed (Celerity) of a “Deep-Water” Wave Speed S can be expressed simply in terms of wave period T: S (m/s) =1.56 T (s) S=1.56 T for T= 1 sec., S=1.56 m/s for T= 10 sec, S= 15.6 m/s, (or about 56 km/hr) Thus, the longer the period the greater the celerity Period (secs) Celerity (m/sec)

27. Speed (Celerity) of a “Deep-Water” Wave This comes from the relation between wave speed, properties of water and acceleration due to gravity. What makes a wave move? S (m/s) =1.56 T (s) S=1.56 T

28. Speed (Celerity) of a “Deep-Water” Wave This comes from the relation between wave speed, properties of water and acceleration due to gravity. What makes a wave move? Water molecules are pushed together by forces that are transmitted via the wave. Think of the particles in the animation by D. Russell ( http://www.acs.psu.edu/drussell/Demos/waves- intro/waves-intro.htm l ). When the molecules are pushed together the water level rises, but water has low viscosity, so it can’t stay like that. The ‘hill’ of water that’s created spreads out, and as it does so, the wave moves! http://www.acs.psu.edu/drussell/Demos/waves- intro/waves-intro.htm l Gravity is clearly important, so are the physical properties of water. If we simplify things, we find that wave speed S is related to gravitational acceleration, g, and wave period T as: S = g T / 2 ,

29. Speed (Celerity) of a “Deep-Water” Wave This comes from the relation between wave speed, properties of water and acceleration due to gravity. What makes a wave move? Gravity is clearly important, so are the physical properties of water. If we simplify things, we find that wave speed S is related to gravitational acceleration, g, and wave period T as: S = g T / 2 , S = g T / 2 , S = 9.8 m/s 2 T / (2 * 3.141592)

30. Speed (Celerity) of a “Deep-Water” Wave This comes from the relation between wave speed, properties of water and acceleration due to gravity. What makes a wave move? Gravity is clearly important, so are the physical properties of water. If we simplify things, we find that wave speed S is related to gravitational acceleration, g, and wave period T as: S = g T / 2 , S = g T / 2 , S = 9.8 m/s 2 T / (2 * 3.141592) S (m/s) = 1.56 T (s)

31. Speed (Celerity) of a “Deep-Water” Wave What makes a wave move? Gravity is clearly important, so are the physical properties of water. If we simplify things, we find that wave speed S is related to gravitational acceleration, g, and wave period T as: S = g T / 2 , S (m/s) = 1.56 T (s) Also need to appreciate the relationship between wavelength (L) and speed (S) Note that: L = S T L (m) = S (m/s) T (s)

32. Speed (Celerity) of a “Deep-Water” Wave What makes a wave move? Gravity is clearly important, so are the physical properties of water. If we simplify things, we find that wave speed S is related to gravitational acceleration, g, and wave period T as: S = g T / 2 , S (m/s) = 1.56 T (s) Also need to appreciate the relationship between wavelength (L) and speed (S) Note that: L = S T L (m) = S (m/s) T (s) S (m/s) = L (m) / T (s) Recall that we can evaluate the relationship between L and T or L and S by combining these equations:

33. Speed (Celerity) of a “Deep-Water” Wave What makes a wave move? Gravity is clearly important, so are the physical properties of water. If we simplify things, we find that wave speed S is related to gravitational acceleration, g, and wave period T as: S = g T / 2 , S (m/s) = 1.56 T (s) Also need to appreciate the relationship between wavelength (L) and speed (S) Note that: L = S T L (m) = S (m/s) T (s) Recall that we can evaluate the relationship between L and T or L and S by combining these equations: S (m/s) = 1.56 T (s) L (m) = S (m/s) T (s) L = 1.56 T 2

34. Speed (Celerity) of a “Deep-Water” Wave What makes a wave move? S (m/s) = 1.56 T (s) Also need to appreciate the relationship between wavelength (L) and speed (S) Note that: L = S T L (m) = S (m/s) T (s) S (m/s) = L (m) / T (s) Recall that we can evaluate the relationship between L and T or L and S by combining these equations: S = 1.56 T L = S T or T = L/S S = 1.56 L/S S 2 = 1.56 L S = (1.56 L) 1/2 or S = 1.25 √L

35. Speed (Celerity) of a “Deep-Water” Wave What makes a wave move? S (m/s) = 1.56 T (s) Also need to appreciate the relationship between wavelength (L) and speed (S) Note that: L = S T L (m) = S (m/s) T (s) S (m/s) = L (m) / T (s) Recall that we can evaluate the relationship between L and T or L and S by combining these equations: S = 1.56 T L = S T or T = L/S or S = L/T L = 1.56 T 2

36. Speed (Celerity) of a “Deep-Water” Wave What makes a wave move? S (m/s) = 1.56 T (s) Also need to appreciate the relationship between wavelength (L) and speed (S) Note that: L = S T L (m) = S (m/s) T (s) S (m/s) = L (m) / T (s) Recall that we can evaluate the relationship between L and T or L and S by combining these equations: S = 1.56 T L = S T or T = L/S or S = L/T L = 1.56 T 2

37. Summary of Deep-Water Wave Properties Wavelength, Period and Velocity of Deep- water waves are interrelated

38. Shallow-Water Waves Speed is related to water depth d: S =(g d) 1/2 Waves are slower in shallower water: d=10 m, s=10 m/s; d=5 m, s=7 m/s; d=1 m, s=3.2 m/s piru.alexandria.ucsb.edu/~tierney Wavelength (L) and speed (S) decrease while period T remains constant S = L/T

39. Types of Waves Defined in terms of Water Depth Only some of the molecules in the water column are involved in a deep-water wave…

40. Wave Motion is Oscillatory Remember: a wave is energy passing through the water, not a parcel of moving water

41. Wave Motion is Oscillatory

42. Remember: a wave is energy passing through the water, not a parcel of moving water

43. Wave Motion is Oscillatory Remember: a wave is energy passing through the water, not a parcel of moving water There is virtually no “net” forward motion of a particle or “parcel” of water --much like riding on a Ferris Wheel --in fact, the “orbit” that a particle in water experiences with passage of a wave has diameter H (wave height) at the surface

44. S= Wave speed (or celerity) in meters/sec T= wave period in seconds (time for one wavelength to pass) http://www.acs.psu.edu/drussell/Demos/waves-intro/waves-intro.html

45. HELP! HELP! HELP! I’m stuck in one place… I thought I could just sit Here and ride along with the waves But I’m not moving. There is virtually no “net” forward motion of a particle or “parcel” of water

46. A. higher in the winter, in part because bacteria migrate south in winter B. higher in the winter, in part because sunlight is stronger in winter C. lower in the summer, in part because thermal stratification is greatest in summer D. lower in the summer, in part because thermal stratification is weakest in summer Eutrophication causes dissolved oxygen levels to be __:

47. Waves If you don't have a calculator, work with someone who does, or try without one A.Celerity is: 0.64 m/s B.Celerity is: 1.56 m/s C.Celerity is: 0.156 m/s D.Celerity is: 156 m E.Celerity is: 15.6 m/s Deep water waves: 1) S = L / T, 2) S = 1.56 T, 3) L =1.56 T 2 (S is speed in m/s, T is period in sec, and L is wavelength in m.) Think about a deep-water wave with 1-second period? What is the speed of the wave crest?

48. Waves If you don't have a calculator, work with someone who does, or try without one A.Celerity is: 0.64 m/s and Wavelength is 1.42 m B.Celerity is: 1.56 m/s and Wavelength is 1.56 m C.Celerity is: 0.156 m/s and Wavelength is 0.156 m D.Celerity is: 156 m and Wavelength is 156 m/s E.Celerity is: 1.56 m/s and Wavelength is 156 m Deep water waves: 1) S = L / T, 2) S = 1.56 T, 3) L =1.56 T 2 (S is speed in m/s, T is period in sec, and L is wavelength in m.) Think about a deep-water wave with 1-second period? What is the speed and wavelength?

49. A.0.64 m/s B.156 m/s C.0.156 m/s D.15.6 m E.1.56 Deep water waves: 1) S = L / T, 2) S = 1.56 T, 3) L =1.56 T 2 (S is speed in m/s, T is period in sec, and L is wavelength in m.) What is the speed of a deep-water wave with 100-second period?

50. Deep water waves: 1) S = L / T, 2) S = 1.56 T, 3) L =1.56 T 2 (S is speed in m/s, T is period in sec, and L is wavelength in m.) In deep water, what is the wavelength of a 10-second period wave? a) 1.56 m b) 15.6 m c) 75 m d) 156 m

51. Deep water waves: 1) S = L / T, 2) S = 1.56 T, 3) L =1.56 T 2 (S is speed in m/s, T is period in sec, and L is wavelength in m.) In deep water, how deep does a wave of 10-second period extend? a) 10 m b) 1.56 m c) 5 m d) About 75 m

52. Wind Blowing over the Ocean Generates Waves Capillary waves become gravity waves as their wavelength exceeds 1.74 centimeters. These wind-induced gravity waves (wind waves) continue to grow as long as the wind above them exceeds their speed.

53. Wave size and period. Are they all the same or is there a big one every so often --every 7 th wave?

54. Most ocean waves have a period between 1 and 10 seconds

55. Most waves have a period between 1 and 10 seconds For deep water waves, that means a speed between 1.56 m/s and 15.6 m/s Recall: S = 1.56 T