1. Class 28: Oceanography

2. Class updates:  Reading: Section 15.1-15.3, 16.1-16.2, 16.5 Today’s topics:  Ocean water  Ocean currents  El Nino/La Nina Class 28: Oceanography

3.  Continents: green/tan avg. height 840m  Oceans: blue avg. depth 3800m, cover 66% planet The Oceans

4.  Mostly Chlorine (Cl), Sodium (Na)  Minor amounts: SO 4, Mg, Ca, K  Dissolved salts ~4 % Ocean Water Composition

5. Dissolved ions come from:  Chemical weathering: Rivers dump 2.5 billion tons/yr of dissolved salts  Volcanic activity: -outgassing: sulphur, bromine -hydrothermal circulation: hot water dissolving rocks Salty Origin

6. Ocean is not getting saltier, so where?  Shells/hard parts:  Chemical sediments: clays, oozes Where do ions go?

7. Ocean salt balanced by:  Balancing Water (red) Rain Stream input Evaporation  Balancing Salt (purple) River/volcanic input Reduction by sediments and hard body parts Salt Balance

8. Salinity = amount of salt in the water Factors for balance change over Earth Salinity of Ocean Surface

9. Shallow surface mixed zone (< 450 m) Transition zone (< 1500 m thick) Deep zone Changes with depth

10. Shallow surface mixed zone –mixed by wind and currents –Uniformly warm –Generally higher salinity (surface evaporation) Top: Mixed Zone

11. Transition zone (< 1500 m thick) –Temperature decreases rapidly - thermocline –Salinity decreases rapidly - halocline Middle: Transition Zone

12. Bottom water –Very cold, near freezing < 4˚C –Relatively low salinity Bottom: Deep Zone

13. Thermocline narrow at poles Thermocline-top deep @ ~ 30, thicker @ equator From North to South

14. Ocean conveyor belt Warm @ surface Cold @ bottom Water is moving

15. Warm water cools in North Atlantic Cold water sinks: cold = densest The Water Pump

16. Cold water sinks and flows south along bottom: Atlantic Deep Water

17. Conveyor Belt = simplified Actual surface flow in currents Surface Currents

18. Map flow with oceanographic instruments Current flow is more complex: turbulence Adding complication

19. Persistent winds push water Subtropics: Trades (from E) Mid latitudes: Westerlies Currents and Winds

20. Why do winds and currents go East or West?

21. Coriolis Effect Anything moving from equator (look along arrow) bends to the right

22. El Nino-Step 1 NORMAL CONDITION: Trades (E to W) push water to W Pacific W Pacific water = warm, E Pacific = upwelling cold Air over warm water rises Air over cold sinks

23. El Nino-Step 2 EL NINO CONDITION: Trades (E to W) push less Thermocline flattens: less upwelling cold water Rain moves E: – Australia/Indonesia dry – Peru/Central Am wet

24. El Nino-Step 3 LA NINA CONDITION: Trades (E to W) push extra hard E Pacific = more upwelling cold Air over warm water rises Air over cold sinks

25. Southern Oscillation El Nino and La Nina are the extreme hot and cold parts of the Southern Oscillation cycle