Download GEF2610-avslutning

GEF2610 Physical Oceanography
Course content
The physical structure and circulations of the oceans, and the
physical processes influencing them.
Learning outcomes
The students shall have knowledge about the physical properties of
ocean waters, understand concepts like stability and potential
density, and be able to describe the energy exchange with the
atmosphere. They shall know how the standard instruments are
functioning and understand the meaning of observations presented
in a T-S diagram. The students shall have a good overview of the
general oceanic circulation, understand the driving forces and
mechanisms behind the different types of circulation, and know
where in the world oceans bottom water is formed and where
upwelling occurs.
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Ocean dimensions and extensions
Physical properties of ocean water
Chemical components of ocean water
Standard instruments
Forces; Equation of Motion
Energy exchange with the atmosphere
Physical structure of the oceans
General oceanic circulation
Waves
Tides
Ocean dimensions and extensions
• Names of the different oceans
• Topography of the different oceans
Sand waves
Relative dimensions of atmosphere
and oceans
Physical properties of ocean waters
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Temperature, salinity, density
Compressibility
Potential temperature and density
Freezing point
Specific heat (heat capacity)
Latent heat of evaporation
Latent heat of freezing
Optical properties
Acoustical properties
Translational motion in gases
Light in the sea
Snell’s Law of Refraction
4
sin i  sin j
3
Vertical attenuation
E ( z )  E0 e
K z
Fig. 3.9 Optical pathways to an ocean color sensor
(from Robinson, 1983).
Fig. 3.10 Global chlorophyll concentration in mg/m3 for the
ocean and Normalized Difference Vegetation Index
(-1 to +1) for the land surface for Sept. 97 – Aug. 98.
Sound in the sea
Snell’s Law of Refraction
sin i sin j

vi
vj
Spherical attenuation
2
0
2
R c ( R  R )
 ( R )  0
e
R
0
Chemical composition of ocean
water
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Principal constituents
Constant relative composition of seawater
Gases in seawater (O2)
Methods for determination of salinity
Methods for determination of density
Standard instruments
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Reversing thermometers
Water samplers (e.g. NIO bottles)
ST electronic bridges
CTD sensors
Irradiance meters
Secchi disk
Echo sounders
Current meters
Equation of Motion
     
a b c  F  g T
Simplified models
•Hydrostatic equilibrium
•Geostrophic current
•Ekman spiral
•Equilibrium tide
Hydrostatic equilibrium –
hydrostatic pressure
 
0bg
h
p (h)  g   ( z ) dz  p (0)  g  h
0
Geostrophic current
  
0  b c  g
g
v  tan( )
f
Ocean dynamic topography
Tuva
Ekman spiral – wind current
 
0cF
Wind speed
Equilibrium tide
  
0  b  g T
Energy exchange with the
atmosphere
• Kinetic energy (currents, waves)
• Radiative energy (shortwave, longwave)
• Heat exchange (latent heat of evaporation,
latent heat of freezing, heat conduction)
Budgets
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Heat budgets
Volume budgets
Salt budgets
Knudsen’s Relations
General oceanic circulation
• Surface currents
• Interaction between atmospheric wind and
pressure systems and the major oceanic gyres
• Estuarine circulation
• Upwelling
• El Niño (ENSO)
• Thermohaline circulation
• Vertical convection
• Bottom and deep-water formation
Polarfront
Estuaries
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Estuaries
Fjords
Estuarine circulation
Deep water exchange in fjords
Front: brackish water / sea water
Gåsøyrenna: T and S 04.04.2008
salinity
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5
10
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25
30
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10
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Depth
30
S-Gaasoy
S-Gaasoy-feb
T-Gaasoy
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60
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T-Gaasoy-feb
Gåsøyrenna: Density 04.04.2008
Density - 1000
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10
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Depth
30
Gaasoy
Gaasoy-feb
40
50
60
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Global distribution of temperature,
salinity, and density
• Relationship between temperature,
salinity and the large-scale pressure and
wind systems at the surface
• Typical vertical profiles at low, middle and
high latitudes
Waves
Wind waves
Significant wave height :
the average height of the highest
third of the waves.
Wave height depends on:
• speed (the force of the wind);
• duration (the time the wind has been blowing);
• fetch (the length of the area the wind is blowing
over).
Wave height definition for a regular
wave
Wave height definition for an
irregular sea surface
Histogram of wave heights
Wave speed (phase velocity)
• Short waves (deep water waves)
gL
0.5 1
2
c
 1.25m s  L  1.56m s T
2
• Long waves (shallow water waves)
including tsunamies and tides
c  g h  3.15m0.5 s 1  h
Wave height
Storm
Typhoon Wipha
Earth – Moon Orbit
Tides
• Equilibrium tide (spring and neap tide,
diurnal inequality)
• Real tides in the ocean
M2 amplitude
Bay of Fundy; High Tide
Bay of Fundy; Low Tide
Saltstraumen;
mean speed 4-5 m/s, max speed 10 m/s?
Ice in the sea
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Slush, grease ice
Pancake ice
Pack ice
Hummocs
Icebergs
Grease and pancake ice
Pancake ice
Pack ice
Iceberg
Iceberg
GLACIER