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Oceanography

• Composite science that draws methods and

knowledge from biology, chemistry, physics, and

geology to study all aspects of our world’s

oceans.

Some Boring Numbers

• The area of the earth is 510M km2

• The area of the oceans and marginal seas is

360M km2

• The area of the continents is 150M km2

• The northern hemisphere is 61% water and 39%

land

• The southern hemisphere is 81% water and

19% land

The World’s Oceans

• Pacific▫ Largest; Bigger than the Atlantic plus the Indian

Ocean.

▫ Slightly more than ½ of the world’s waters

• Atlantic▫ Center of a nearly parallel continental margin

▫ Shallowest

• Indian▫ Smallest

▫ Southern Waters

Comparison of Oceans and

Continents• Volume – all land is just one eighteenth that of

the oceans

• Relative levels (elevation, depth)

▫ The average elevation above sea levels is 840

meters

▫ The average depth of the ocean is 3800 meters

Physical Properties of Sea Water

• Composition

• Salinity

• Light Penetration Zones

• Temperature

• Pressure

• Density

Composition

Salinity

• Salt content in water

• Average for:

▫ Salt Water

30 – 35 ppt

▫ Brackish Water

0.5 – 18 ppt

▫ Fresh Water

< 0.5 ppt

Light Penetration Zones

Temperature

• Temperature layers

• The effect of

salinity and pressure is the

same for every

temperature

Water Pressure

• Pressure – a force that acts on an area

• Pressure increases by one atmosphere every 10

meters in depth in the water column

• One atmosphere is 14.7 pounds per square inch

Density

• The average sea water density is 1027 kg/m3

• There are 2 main factors that make more or less

dense than 1027 kg/m3

• These are temperature and salinity

• Cold water is denser than warm water

• Saltier water is denser than fresh water

• Temperature has a greater effect on density than

salinity

Motions of the oceans

• Currents

• Waves

• Tides

Currents

• Ocean currents move water continuously along

specific pathways, often across vast distances.

• This happens both on the surface and in the

deep ocean.

• Currents are driven by the wind across the

ocean’s surface.

Current Facts

• Persistent, dominantly horizontal flow

• Heat exchange between the poles and the

equator

• Surface currents are powered by the wind

• Gyres – circular movement of a large ocean

current

• Transports organisms, nutrients and pollution

across vast distances

Tides

• Is the rise and fall of sea levels caused by the

combined effects of the gravitational forces

exerted by the moon and the sun and the

rotation of the earth.

Waves

• Factors that affect the waves

▫ Speed of the wind

▫ Time of the wind

▫ Distance of the wind (fetch)

• Fetch

▫ the length of water over which a given wind has

blown