OCEAN PROPERTIES, STRUCTURES, AND MOTIONS

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OCEAN PROPERTIES, STRUCTURES, AND MOTIONS

• Overview of the Oceans
• Properties Effecting Motion
• Factors Determining Structure
• Ocean Circulation
• Shallow Wind Driven
• Deep Thermohaline
• http//www.ifremer.fr/lpo/cours/dynamique/diapos

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I. Overview of the Oceans
? Why is the ocean a unique fluid? A
geophysical fluid, like the atmosphere (Earths
rotation important) Solid lateral
boundaries, unlike the atmosphere (can support
pressure gradients) Density depends on
temperature, salinity, and pressure (depth)
Contained in a thin shell average depth (-4
km) only 1/1700 the earths radius
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Are the Oceans Important?
70 of the earths surface 97 of the
available terrestrial freshwater 300 times
the mass of the atmosphere 1200 times the
heat capacity of the atmosphere Large
capacity to store carbon ( CO2 ), other gases
and pollutants
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II. Ocean Properties
A Active Temperature (T), Salinity
(S)   ? Density (?)   ? Pressure Forces
(p)   ? Motions (Deep) (u, v, w)    B
Passive Phytoplankton   Nutrients   Ox
ygen   CFCs   Helium -
Tritium   Carbon (Bomb, CO2 )   etc.
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III. Ocean T and S Structure
Sources Sinks
Heat (T) Solar radiation Evaporation
Radiation from clouds Radiation from surface
Warm air Cold air
Ice formation Ice melt
Salinity (S) Evaporation Precipitation (90 of evaporation)
River runoff
Ice formation Ice melt
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Implications of sources and sinks all being at
the surface !!
? Extrema of both T and S (warmest, coldest,
freshest, saltiest) must be at the surface
? Dense surface water (polar) sinks to fill up
deep water ocean basins, then pressure effect
acts to make bottom water the most dense
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The wind mixes near surface T and S
50 meters in stabilizing regions (less
dense) i.e., tropics, summer mid-to-high
latitudes   400 meters in destabilizing
regions (more salting and cooling) i.e.,
mid-latitude evaporation   Little wind
influence on convection regions
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IV. Ocean Circulation
Drivers earths rotation wind heating
and freshening  attraction of the moon
These forcings combine to produce diverse ocean
flows, strongly influenced by vertical
stratification and by lateral boundaries
(coastlines). waves and tides (x)  turbul
ent eddies (x)  surface currents (1)  deep
currents (2)
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Newtons Law
Force mass acceleration ? internal
pressure Coriolis (earths
rotation) ? external gravity (heavy water
sinks) ? friction surface wind stress
dissipation Some observed balances
Inertial, Coriolis acceleration, mixed layer
Ekman, Coriolis wind, mixed layer
Geostrophic, Coriolis pressure, interior
Equatorial, wind pressure, upper ocean
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Wind Driven Circulation
How does it reach deep 800m ? Note 2
mls along western boundaries   1
mls equatorial near surface   10 mls interior
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Global Conveyor Belt
Simplistic cartoon of the effect of all motions
in circulating water parcels throughout the
worlds ocean, both deep and shallow.
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http//www.ifremer.fr/lpo/cours/dynamique/animatio
ns/traj.mpeg