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Oceans
A large body of water bounded by
features such as landforms,
currents, and underwater
topography
Four Major Oceans on Earth
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Atlantic Ocean
Second largest ocean
• Longest from North to South
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Arctic Ocean
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Smallest ocean
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Indian Ocean
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Pacific Ocean
Largest ocean
• Covers 33% of the Earth
• Contains 50% of Earth’s salt water
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Composition of the Ocean
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Dissolved gases
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greater percent in cold water
1.
Nitrogen
2.
Oxygen
3.
Carbon Dioxide
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Salinity
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A measure of the dissolved solids in seawater
Salinity
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Average ocean salinity = 34.5 ppt. (parts per thousand)
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If you evaporate 1000 grams of sea water, 35 grams of
solid minerals (salts) will be left behind
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Measured with instruments that test for electric
conductivity
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The more conductive, the higher the salinity
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Sources of ocean salinity include:
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Volcanoes, erosion carried by glaciers, streams, and waves breaking
on shore
Changing Salinity
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Lower than average salinity where
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Salinity decreases where large amounts of fresh water are
entering any ocean
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Rate of fresh water input exceeds rate of evaporation.
Mouth of a river
Where glaciers enter the ocean
Areas of heavy rainfall (equator)
Example: Baltic Sea Salinity = 30 ppt because many rivers
and glaciers drain into it
Changing Salinity
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Salinity increases where climates are hot and dry
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Evaporation is taking away fresh water and leaving salt
behind
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Higher than average salinity where:
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Rate of evaporation exceeds rate of precipitation.
Latitudes between 20° - 30° North and South latitude
Ex: Mediterranean Sea and Red Sea
Salinity = 40 ppt
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Sea ice forming in polar waters
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Only fresh water forms ice and the salt gets left behind
Ions in Ocean Water
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Main salt is sodium chloride (NaCl)
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Common ions are Cl-, Na+, SO42-, Mg2+, Ca2+, K+
Mining Ocean Water
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Most elements including gold, silver, copper, uranium are
present in quantities too small to extract at a profit
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Magnesium is sometimes obtained from seawater
Pressure
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The force per unit area
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Pressure at the bottom of the Mariana Trench is 1000 times
greater than atmospheric pressure.
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Depth is about 11,000 m or 36,000 ft.
There is so much water pushing down from above at this depth
that the force is 7.8 tons per square inch
Doubling water depth doubles the pressure
Density
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The mass per volume of an object
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Density of fresh water is greatest at approximately 4°C
(40°F)
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Increasing or decreasing temperature from this number
causes a decrease in density
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As salinity increases, the temperature of maximum density
and the freezing temperature decreases.
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Seawater density and temperature are inversely
proportional
As TEMPERATURE of seawater increases, DENSITY decreases
• As TEMPERATURE of seawater decreases, DENSITY increases
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