Oceans

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. 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(3.3-3.8%) Main salts/minerals present in oceans (ppt): 1. NaCl (halite) 23.48 (about 2.35%) 2. MgCl2 4.98 (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? 1. Weathering of rocks and minerals 2. Outgassingfrom 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

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

38. Why is Ocean Circulation Important? • Transports heat from equator to poles • Transport nutrients and organisms • Influences weather and climate

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 10-15 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. Deep Ocean Currents (Thermohaline) Two factors are important in creating a dense mass of moving water: 1. Temperature 2. Salinity *Colder and salty water is denser than warmer, less salty water.

46. Thermohaline Circulation - The Ocean Conveyor