Introduction to Ocean Circulation - Geography 163

1. Introduction to Ocean Circulation - Geography 163 • Wind-driven circulation of major gyres & surface currents • Buoyancy-driven circulation linking the major gyres & the global conveyor belt • Coastal circulations & land-ocean interactions • Build from physical principles (w/out math)

2. Approach • First principles do “work” • Build descriptions from first principles • Do not bludgeon students with calculus • Work with available data sets

6. Why do we care? • Climate • Global heat & water cycles • Weather & weather/climate prediction • Global biogeography & biogeochemistry • Species ranges & adaptation to global change • Fossil fuel CO2 sequestration • Marine resources • Renewable (fisheries) • Non-renewable (oil, etc.)

7. Global Climate Change IPCC [2007]

8. Global Heat Transport How can it be constant?

9. Global Heat Transport

10. Global Heat Transport 1015 W = 1 Petawatt

11. El Niño

12. El Niño

13. El Niño

14. SST Departures (oC) in the Tropical Pacific During the Last 4 Weeks • During the last 4-weeks, equatorial SSTs were more than 1.0°C above average between 165°E and 120°W and near the western S. American coast.

15. Niño Region SST Departures (oC) Recent Evolution The latest weekly SST departures are: Niño 4 1.0ºC Niño 3.4 1.1ºC Niño 3 0.7ºC Niño 1+2 0.1ºC

16. Recent Evolution of Equatorial Pacific SST Departures (oC) Since the beginning of June 2009, SST anomalies have been at least +0.5°C across most of the equatorial Pacific. During December 2009, positive SST anomalies increased across much of the equatorial Pacific. From late December 2009 to mid-February 2010, positive SST anomalies decreased across portions of the central and east-central Pacific. Recently, positive SST anomalies have decreased over the central Pacific. Time Longitude

17. NPP & Climate NPP = Net Primary Production rate of C fixed by phytoplankton Chlorophyll is found in all plants & phytoplankton Averages are from persistently warm ocean (SST> 15C) From Behrenfeld et al. [2006]

18. NPP & Climate

19. Biogeography

20. Biogeographical Boundaries

21. Biogeography

22. CO2 Sequestration It’s gotta go somewhere...

23. CO2 Sequestration This is where.

24. Climate & Fish Pacific Decadal Oscillation Warm phase - southern Cool phase - northern We’re now in a cool phase…

25. Introduction to Ocean Circulation - Geography 163 • Wind-driven circulation of major gyres & surface currents • Buoyancy-driven circulation linking the major gyres & the global conveyor belt • Coastal circulations & land-ocean interactions

26. Scales • Ocean basins are wide & shallow • Typical scales are 104 km across and 5 km deep • “Spit on a basketball” • Aspect ratio has important implications • Horizontal velocities are >> vertical velocities • Horizontal property changes are << vertical ones

27. Global Bathymetry

28. Hyposgraphic Curve

29. Wind-Driven Gyres

30. Global Ocean Circulation

32. Global Wind Climate

33. Conveyor Belt

34. Net Air-Sea Heat Flux

35. Atlantic Temperature eWOCE gallery – www.ewoce.org

36. Atlantic Salinity

37. Atlantic Oxygen

38. Atlantic Phosphate

39. Coastal Upwelling

40. Coastal Upwelling

41. Coastal Upwelling July 1992 AVHRR Ch 4

42. Summary • Importance of large-scale ocean circulation • climate, biogeochemistry, marine resources • Characteristic “Types” of Ocean Circulation • Patterns of circulation can be generalized for different regions • Suggests that dynamical processes are the same • Wind-driven, Buoyancy-driven & Coastal • Scales - “spit on a basketball”