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 andContinents• 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
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