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.
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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
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Convention on International Trade in Endangered Species CITES
Required reading on the course web site: Lecture Notes link
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Chesapeake Bay Report Card
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Nutrients that cause Eutrophication and, ultimately, Hypoxia
include A.Nitrogen B.Calcium C.Phosphorous D.Gatorade E.(A) and
(C)
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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
Slide 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
Slide 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
Slide 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
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http://www.chesapeakebay.net/
Slide 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
Slide 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
Slide 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
Slide 14
Waves! in the Ocean Nearly all waves in the ocean are produced
by Wind What is a Wave?
Slide 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
Slide 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
Slide 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
Slide 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
Slide 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
Slide 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
Slide 21
Deep water wave vs. Shallow water waves
Slide 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
Slide 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
Slide 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
Slide 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
Slide 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)
Slide 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
Slide 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 cant stay like that. The hill of
water thats 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
,
Slide 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)
Slide 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)
Slide 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)
Slide 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:
Slide 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
Slide 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
Slide 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
Slide 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
Slide 37
Summary of Deep-Water Wave Properties Wavelength, Period and
Velocity of Deep- water waves are interrelated
Slide 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
Slide 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
Slide 40
Wave Motion is Oscillatory Remember: a wave is energy passing
through the water, not a parcel of moving water
Slide 41
Wave Motion is Oscillatory
Slide 42
Remember: a wave is energy passing through the water, not a
parcel of moving water
Slide 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
Slide 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
Slide 45
HELP! HELP! HELP! Im stuck in one place I thought I could just
sit Here and ride along with the waves But Im not moving. There is
virtually no net forward motion of a particle or parcel of
water
Slide 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 __:
Slide 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?
Slide 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?
Slide 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?
Slide 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
Slide 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
Slide 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.
Slide 53
Wave size and period. Are they all the same or is there a big
one every so often --every 7 th wave?
Slide 54
Most ocean waves have a period between 1 and 10 seconds
Slide 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