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"To the dull mind all nature is leaden. To the illumined mind the whole world burns and sparkles with light." -- Ralph Waldo Emerson

 OCEAN WATER

Origins  Theory:

• Earth's primordial (original) atmosphere of lighter elements (primarily H) blown away by the sun's energy.

 

• Early earth violently volcanic.
• Volcanoes spew many gases.


e.g.:

• H₂O
• CO₂
• N₂

Condensing water eventually filled basins and covered much of the planet.

Composition of today's Atmosphere

Composition

• Earth covered with about 70% water (not just fresh water).

• Contains dissolved minerals, including different salts,

e.g.:

• NaCl
• KCl

• Volcanoes
• River runoff

Salinity

• A measure of the amount of solids dissolved in seawater.

• Na - sodium
• Cl - chlorine
• Mg - magnesium
• SO₄^2- - sulfate
• Ca - calcium
• K - potassium

They are removed:

• By biological processes:

For instance, used by:
 

• Algae - for varied life processes.
• Animals:
• Calcium for bones and shells.
• Silicon and calcium for shells.
• Diatoms have silicate shells.

• By sedimentation:

• Of things like iron coming out of solution and becoming sediment.

• Of animals and plants that have used these substances, becoming sediment after death.

OCEAN CURRENTS

Ocean Currents from Space

Ocean Current Map 1

Ocean Current Map 2

Current Marine Data - clickable

• Surface currents

Horizontally moving water. "Rivers" in the ocean. Moves water all over the globe. Upper few hundred meters of ocean.

The Gulf Stream

• From equator past U.S. east coast.
• Warms eastern U.S. climatically.

Antarctic Circumpolar Current

• Strongest surface current.
• Only one to circumnavigate globe.

What puts the currents where they are?

• Continents
• Coriolis Effect
• Deflects moving fluids to right, in No. Hemisphere.
• Deflects moving fluids to left, in So. Hemisphere.

What are some effects of surface currents?

• Transfer a lot of heat from equatorial regions toward poles.

• Store heat from sun and gradually conduct it to the atmosphere.

• Influence climate on nearby lands.


e.g.

• Iceland
• So. Alaska

• Upwelling

• Deep ocean water brought to surface.

• Caused by the effect of wind blowing across the surface of the water which brings water up from below to fill the gaps.

•  

  MIXING

  Surface currents are horizontal mixing.

  Upwelling is an example of vertical mixing.

  • An example of both vertical and horizontal mixing is:

   

• Density Currents
   

  • Occur when water moves because of differences in density.

  • Denser seawater sinks.

  • Less dense seawater rises in response.

    Causes of density differences:

  • Temperature

  • 
    - Cold water is denser than warmer water.

  • Salinity

  • 
    - More saline water is denser than less saline and fresh water.

  • Pressure can be a factor affected by both temperature and salinity, and thus affect density.

  
  Mixing
   

  • Dense water descends, vertically,

  • Pushing less dense water upward and other dense water horizontally.

  • Creating a horizontal current along the ocean floor.

  World Current examples:
  

  • In the North Atlantic

  • And around Antarctica

  • Water freezes, but most salt does not stay in the ice.

  • The surrounding water gets saltier, and is very cold, so it gets:

  • Denser, and sinks,

  • Driving water below toward the equator along the seafloor, while

  • Warm water at the equator is pushed polewards along the surface.

  • Some cooler water from below rises to the surface and is warmed, becoming less dense and mixing its greater salinity in with the water already there.

  • The Mediterranean Sea

  • Only a small outlet to Atlantic,

  • Warm, so there is much evaporation,

  • Increasing salinity,

  • Therefore increasing density flows along seafloor out into Atlantic and down, cooling off and adding to the salinity of the Atlantic.

   

  •  WAVES AND TIDES
     

  Waves

  • Movement of energy, but not matter, ultimately,

  • Through empty space (radiation),

  • Through matter: oceans, earthquakes.

  Wave Structure   Wavelength Crest Trough Wave Height

  From a Navy Website Check: NOAA, The Navy Check: A Shockwave animation explaining waves.

  Wave movement
   

  Like falling dominoes, parcels of water don't go very far.

  • A Moving Wave web site.

  • They transfer the energy to the next particle in line.

  Breakers

  • Form because the bottom of the wave,

  • under the surface,

  • is cut off by the rising shore and

  • the top falls forward.

  Causes of waves
   

  Wind
   

  • Causes the waves familiar on seashore and lakeshore.

  • Wind "piles" water up and the resulting waves travel almost without end....

  TIDES

  • One "wave" with a wavelength half of a world long.

  • Crest is called "high tide"

  • Trough is called "low tide"

  High-low tide cycle takes 12 hours, 25 minutes:

  So, at any particular location:

  About 2 high tides a day,

  and 2 low tides.

  CAUSED BY:

  Gravity of the moon interacting with the sun.

  • Moon pulls on earth as earth pulls on moon.

  • Oceans respond more noticeably than land.

  • "Wavecrests" on opposite sides of earth.

  • "Troughs" in between:

   

  When earth, moon, sun line up,

  • higher than normal high tide –

• called "spring tide"

• When earth, moon, sun form right angle,
  • lower than normal low tide –
    

  called "neap tide"

  See Spring and Neap Tides in Action

• Tidal Electrical Power

• Some locations, for geographical reasons, have unusual high and low tides –
  [Highest Tides in the World ]
  • A large "tidal range": The difference between high and low tide.
  • These locations can be set up like a hydroelectric dam to produce electricity:

Links:
Satellite data provided by The Living Earth® Inc./Earth Imaging © 1996, All Rights Reserved.