1. Oceans

2. Why study the ocean? One of the last frontiers
Biological & mineral resources
Food & oil shortages on land
Influences weather & climate
Travel & communication

3. Oceanography
the science of our oceans that mixes biology, geology, chemistry, and physics (among other sciences) to unravel the mysteries of our seas.

4. Divisions of Oceanography
Chemical Oceanography – study of chemical reactions
Biological Oceanography – study of living things in their environment

5. Divisions of Oceanography (cont.)
Physical Oceanography – study of changes in motion of sea water
Geological Oceanography – study of sediments & topography

6. Covers 71% of the Earth’s surface Salt Water 97% of all water on Earth
The Global Ocean
Covers 71% of the Earth’s surface
Salt Water
97% of all water on Earth
Where is the “other” water?

7. The Hemispheres of the Earth
Northern Hemisphere
39% land
“Land Hemisphere”
Southern Hemisphere
19% land
“Water Hemisphere”

9. Divisions of the Global Ocean
Pacific Ocean
Atlantic Ocean
Indian Ocean
Arctic Ocean
Southern Ocean

10. Distinguishing Characteristics of Oceans
Size
Currents
Water Masses
Submarine Ridges
Some definable Land Boundaries

11. Pacific

12. Pacific Ocean Largest and Deepest Holds 52% of Earth’s ocean water
Covers 33% of Earth’s surface
Average depth = 4.3 kilometers (2.7 miles)
Mountain building along margins
Abundant islands (mostly volcanic)
Marianas Trench 6.8 miles deep

13. Atlantic

14. Atlantic Ocean 2nd largest ocean 26% of Earth’s ocean water
Avg. depth = 3.9 km (2.4 miles)
Mid-Atlantic Ridge
Few islands
Large sediment deposits from rivers (Amazon & Congo – 25% of world’s river discharge)

15. Indian

16. Indian Ocean 3rd largest ocean Avg. depth = 3.9 km (2.4 miles)
20% of Earth’s ocean water
Mostly in the S.Hemis.
Abundant fresh water due to river discharge (Ganges, Brahmaputra, Indus)

17. Arctic

18. Arctic Ocean 4.2% of ocean water Smallest & Shallowest
Surrounds the North Pole
Almost completely surrounded by land
Covered with sea ice most of the year
Extension of the Atlantic

19. Southern (Antarctic) “Defined” in 2000 Starts at 60o S latitude
Surrounds Antarctica
6.1% of ocean water

20. Earth’s Oceans and Seas

21. What is Ocean Water Composed of?

22. Composition of Seawater
Salinity – amount of dissolved salt in water; usually expressed as parts per thousand (ppt)
Average salinity = 33 – 38 ppt ( %)
Main salts/minerals present in oceans (ppt):
1. NaCl (halite) (about 2.35%)
2. MgCl (about 0.50%)
3. Na2SO4 3.92
4. CaCl2 1.10
5. KCl 0.66
6. NaHCO3 (Sodium bicarbonate) 0.192
7. KBr 0.096
8. H3BO3 (Hydrogen borate) 0.026

23. Where do the salts come from?
Where do the salts come from?
1. Weathering of rocks and minerals
2. Outgassing from Earth's interior
3. Hard parts of marine organisms (i.e., shell material)

24. What affects salinity?

25. What affects salinity? Increase salinity (remove water) –
Evaporation
Formation of sea ice
Decrease salinity (add water) –
Precipitation
Sea ice melting

28. Ocean Temperature
Surface water temperature varies with amount of solar radiation received
Variation with depth –
Low latitudes = rapid decrease in temp. w/depth (thermocline)
High latitudes = no rapid change in temp. w/depth

30. Ocean Density Density = mass/volume
Depends on: temperature and salinity
Determines water’s vertical position in the ocean
Pure water = 1 g/cm3
Remember – densest water is COLD & SALTY

32. Ocean Layers Determined based on density:
1. Surface mixed zone (Epipelagic): 2%, warmest from solar energy, mixed by waves, 300 m, most saline
2. Transition zone (Mesopelagic): 18%, “Twilight Zone”, 200 – 1000 m, includes thermocline
3. Deep zone (Bathypelagic): 80%, “Midnight Zone”, just slightly above or below freezing, not very saline

34. Light in the Ocean Photic Zone - Sunlit layer of water
Deepest in tropics
Typical value: 100 meters
Photosynthesis occurs here
Most ocean life found here
Aphotic Zone – Complete darkness

36. 15 ft. deep
Ocean depth 14,500 ft.
Midway islands area

37. Circulation Atmospheric Circulation Surface Ocean Circulation
Depends on density
Surface Ocean Circulation
Depends on the wind
Deep Ocean Circulation

38. Why is Ocean Circulation Important?
Transports heat from equator to poles
Transport nutrients and organisms
Influences weather and climate
4 th century BC ,Pytheas of Massalia, a Greek ship captain, explored eastern Atlantic
Okeanos (Greek for “Great River”) because he found the ocean flowing south (Canary Current) and thought it was a river too wide to cross.

40. Ocean Circulation

41. Surface Currents
*Coriolis Effect - ocean currents are directed to the right (clockwise) in the northern hemisphere and to the left (counterclockwise) in the southern hemisphere
*Upwelling is the force that vertically moves cooler, nutrient rich water from approximately 1000 feet below the surface to the near surface.
Where winds blow towards the equator and parallel to the coastline (ex: west coast of California), surface water movement is deflected away from the coast and deeper water is thrust upward to the surface.
This creates a vertical component that causes temperatures drops in surface waters to nearly degrees.
Thus, extensive nutrients like nitrates and phosphates are "upwelled" to the surface and plankton and other fish populations flourish.

42. Upwelling

44. Equatorial to polar heat transport and water flow

45. Thermohaline Circulation
North Atlantic Deep Water (NADW
15 million m3 of near surface water descend into the deep ocean each second.

46. Deep Ocean Currents (Thermohaline)
Two factors are important in creating a dense mass of moving water: Temperature 2. Salinity
 *Colder and salty water is denser than warmer, less salty water.

47. Thermohaline Circulation - The Ocean Conveyor