Oceanography

1. Oceanography By Mr. Hagen Oceanography By Mr. Hagen

2. The World ocean: Geological Factors A. General Information • 70-80% water • Ocean most complex • All major basins (oceans) are interconnected B. Transports • Dissolved minerals, heat, organisms • Gigantic carbon sink • Concerns: carbon sequestration. Is there a tipping point? • Keeps planet’s temperature low and relatively constant

3. C. Major Basins • Pacific • Atlantic • Indian D. Ocean moderates world climate • Hotter at the equator • Colder at the poles.

4. Topography of the Ocean Floor • History • At first we used weighted ropes • 1920s, echo sonar, developed further in WWII. • Discovered underwater trenches, basins.

5. Continental Shelf • Underwater extension of the continents land mass • 8% of the total surface of the world • Canyons • Many of the same geological features on land exist underwater • Trenches • Huge canyons (like the grand canyon)

6. Continents Adrift: Plate tectonics • Theory of moving crustal plates • Slowly • Up to 100km thick • Major plates • American, African, Eurasian, Antartic, Indian and Pacific • Geo-Theory still at work • When anything melts, minerals are released in the ocean • Fissures – Hydrothermal vents • Cold water sinks, hot water rises, mixes the ocean • Effects on Marine life by providing minerals. Major ecosystems thrive around the hydrothermal events. A link to prehistoric bacteria

7. Sea Level • 15,000 years ago, 120 meters below present level. • Changes due to global climate events (e.g.) Ice ages • Increased shelf erosion created canyons • 10 meters rise in the sea level in last 3000 years • Global Warming

8. Motion of the Oceans • Waves • Represent mechanical energy • Transferred from wind, earthquakes, landslides, tides and other waves • Travel outward from the nrg source, increase in size relative to nrg.

9. Properties • Wind generated waves affected by: • Velocity of the wind, length of time wind touches the water and duration. • Parts of a Wave • Crest • Trough • Wavelength • Waveheight • Period • Frequency • Speed: wavelength/period

10. When a wave reaches shallow water: • Water rises • Marine organisms must adapt to the pressure of the wave • Varies seasonally: winter has higher crests, summer has longer crests. • Tsunami (giant waves) • Causes: underwater earthquakes • Hundreds of miles per hour, wavelengths up to 100 miles • Up to 100 feet at the shore

11. Tides • What is it? • Rhythmic way of the rise and fall at a fixed point • Effects organisms on the shore • Caused by the gravity of the moon and the earth • Two tides per day • Not constant, why? • Lunar day is 24hrs and 55 minutes. • Size and depth of the ocean effect range and frequency.

12. Three types • Semidurnal – 2 equal low and high tides. E.g. East coast • Diurnal – 1 high and 1 low tide equally. E.g. Gulf of Mexico, Vietnam, Manila • Mixed – 2 low and 2 high tide but are unequal. E.g. West Coast

13. Currents • Circulation effects marine organisms • Tidal currents • Effects of currents • Distribution of substances • A constant mixing of nutrients and spreading “seeds” • Surface and wind driven transports platonic organisms • Plants grow in the direction of currents • Corral grows parallel to the coast. • Thermohaline currents • Driven by heat • Spread dissolved oxygen

14. Coriolis Effect • Ocean rotates in huge circular rivers • Clockwise: Northrnhemisphere • Counterclockwise: Southern hemisphere. • Pressure • Air is 0.1% as dense as water • Determines the distribution of marine organisms

15. Dissolved gases • Oxygen • Most plants and animal are aerobic • Anaerobic = does not require oxygen • Atmosphere is 21% oxygen, solubility of oxygen in coldest parts is less than 1% • Major Source: • Photosynthesis from plants and bacteria • Turbulence: water holds oxygen better with more turbulence • Depth of water: oxygen decreases and as depth increases • Oxygen enters marines organisms through differsion (gills)

16. pH Value • Normal pH of ocean is 7.5-8.4 • Dissolved Nitrogen • Between 10-15ml/L • ½ of all dissolved gases • Source? • Atmosphere, which is 79% • Nitrogen is inert • Must be fixed before using. Nitrogen fixation is done by blue-green algae in the ocean.

17. Temperature Distribution • Effects? • Metabolism • Density • Salinity • Dissolved gases • Differences caused by? • Uneven heating of the planet from the sun • Due to the tilt of the earth

18. Seasonal temp • Effected by the rotation of the earth. • Stable in the abyssal region, equator and poles • Temperature ranges in shallow, estuaries, bays and lagoons will fluctuate dramatically • Thermocline • Change in temperature • Overturn • Upwelling of water. Cold water sinks and warm water rises

19. Effects on Marine Organisms • As temperature decreases, metabolism decreases • Digestion, locomotion all slow down as temperature decreases • Ectotherms • Adapt by becoming dormant (crabs) • Endothermic • Maintain internal temp despite outside • Marine Mammals • Whales, seals and porpoises • Some fish • Albacore, blue fin tuna, great white shark, barracuda • Insulation • Flubber, blood flow

20. Light • Penetration of light is critical to marine organisms • Autotrophs Versus Heterotrophs • Most electromagnetic radiation is reflected back to the atmosphere • 65% of light entering the ocean is absorbed within 1 meter, converted into heat • Photic Zone • 1-100 meters • Green Penetrates further in coastal oceans • Aphotic Zone • 90& of the ocean