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World Ocean Circulation Notes & Midterm Review

Learn about surface and deep water circulations, the foundations of physical oceanography, motion in the ocean, and the global conveyor belt. Discover the forces governing ocean circulation and its practical applications.

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World Ocean Circulation Notes & Midterm Review

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  1. Surface Water & Deep Water CIRCULATION

  2. NOTES • Turn in Homework -2 • Pick Up Homework – 1 • Homework 3 – Assigned Due Next Wednesday • MIDTERM • Get 2 GREEN SCANTRONS from Bookstore • #2 pencil • Exam based on Lecture Notes • 40 Multi Choice Qs • 5 Short Answer

  3. World Ocean Circulation • Traditionally divided into 2 components: • 1) Surface Water Circulation • 2) Deep Water Circulation • Actually Both Influence each other. . . • Best TERM: WORLD OCEAN Circulation • We’ll Review each separately for Simplicity Sake . . .

  4. World Ocean Circulation • Based on Dynamic Physical Oceanography • Describes Ocean based on: • Physical laws & conservation equations in conjunction with • Atmospheric and oceanographic observations • GOAL: • Quantify flow patterns & property distributions in the Ocean • Many PRACTICAL Applications: • Ship Routing • Search and Rescue • Marine pollutant trajectories • OUR GOAL: • Explore the Nature of Ocean Circulation – • become aware of Forces that govern . http://www.mindfully.org/Plastic/Nike-Pacific-Dump-Ebbsmeyer.htm

  5. OUTLINE • World Ocean Circulation • Foundations of Physical Oceanography • Motion in the Ocean • Upwelling/Downwelling • Patterns of Surface water Circulation • Patterns of Deep water Circulation • What Drives Deep water Circulation • Global Conveyer Belt

  6. Foundations of Physical Oceanography • Ben Franklin (1706-1790) • US Postmaster General (reduce transit time) • Publishes First Maps of Gulf Stream • By 1800 many circulation patterns worked out by seaman • Via Trial and error • Little understanding of • Why?

  7. Foundations of Physical Oceanography • Many Early Scientists contributed to • Modern view of Ocean Circulations Patterns (1750-1900) • Based on Convection Currents Model • Ben Thompson, Henry Ellis, John Buchanan, Alex Buchan • Alfred Merz, Geoarge Wust • 1958, Henry Stommel (1920-1992) • Proposed global model of abyssal circulation . . . • Most Important Physical Oceanographer- All time

  8. Deep H2O formation Deep flows. . .. Deep flows Subsurface flows. . .. • 1958, Henry Stommel (1920-1992) • Proposed global model of abyssal circulation Deep H2O formation

  9. OUTLINE • World Ocean Circulation • Foundations of Physical Oceanography • Motion in the Ocean • Upwelling/Downwelling • Patterns of Surface water Circulation • Patterns of Deep water Circulation • What Drives Deep water Circulation • Global Conveyer Belt

  10. Motion in the Ocean – Challenge Questions • The existence of the 4 Big Gyres- Where are they? • How do they arise? See next slides • What direction are their rotations Clockwise or Counterclockwise? • WHY? see next slides

  11. Motion in the Ocean • The existence of the Gyres • How do they arise? V. Walfrid Ekman (1861-1930) • Understand Ekman Transport ((Wind stress)) Friction drags layer below And so on. . . Remember: In N. Hemisphere Coriolis deflects this to Right NOTE: Arrows indicate: -direction -intensity

  12. Motion in the Ocean • Ekman Transport • Challenge Question? What 2 phenomena occur to the currents as you go deeper in depth layers? 1. The currents deflect Right (N. Hemisphere) 2. The currents intensity weakens NOTE: Arrows indicate: -current direction -current intensity

  13. CHALLENGE Question Why do the Gyres spin Clockwise or Counter Clockwise? N. Hemisphere S. Hemisphere

  14. CHALLENGE Question RECALL The Westerlies & The Trade Winds • Provide Wind stress • Under influence of Coriolis • Curves currents to right • Via Ekman Transport clockwise How Should this look in the S. Hemisphere? • NOTE: • There is a mistake • in the Text • – where is it and why? S. Pacific Gyre should be counter clockwise

  15. v • Gyres – • N. Hemisphere = Clockwise • S. Hemisphere = Counter Clockwise • What is so important about Gyres anyway? clockwise Counter clockwise Anthropogenic activity causing harm: See the Great Ocean wasteland. . .KQED http://www.youtube.com/watch?v=g9fEbqxyNl0

  16. WHAT CAN YOU DO? • You’re probably not Going to Stop Using all Plastics • RECYCLE • RECYCLE • RECYLCE! • Santa Cruz one of the best County’s for RECYCLING!!! (#1-6 or higher!) • JUST DO IT • Set an EXAMPLE for you FAMILY, Friends & • the Next Generation 

  17. Geostrophic Flow: The Hill in the Gyre • What does geostrophic stand for? • “Earth-turning” –refers to “flow under influence of Coriolis” • EKMAN Transport Directs H2O to middle of Oceans (Gyres) • Creates sloping Sea Surface (a Hill) • H2O flows from High Pressure to Low pressure • Forms geostrophic currents (gyres) • A balance of: • Horiz. Press. Gradient • Coriolis force

  18. Geostrophic Flow: The Hill in the Gyre • Another rendition

  19. Geostrophic Flow: The Hill in the Gyre • Consequences .. (see TOPEX Satellite Alimeters) • Elevated Sea Surface Heights across the Oceans

  20. Geostrophic Flow: The Hill in the Gyre • Satellite Jason 2001 • 32 cm difference in elevation b/w Pt. A vs Pt. B

  21. Upwelling/Downwelling • What is upwelling? • The flow of subsurface waters to the surface • What are the two types: • Coastal • Equatorial • EQUATORIAL Upwelling nutrients

  22. Satelite Image of Upwelling • Cooler waters in Purple

  23. Upwelling • COASTAL Upwelling (e.g. California) • In N. California, what direction does the Coastal wind Come From? • North (Alaska) Winds . . . . • Surface waters are: • blown west • (via Ekman transp.) • Deep H2O is upwelled to fill gap • Cold water upwelled 

  24. Downwelling • What is it? • the movement of water downward in the water column • Warmer surface water migrates onto the coastline •  VS Versus heading out to sea (UPWELLING)

  25. Serious Upwelling in N. California • Lots of biological Production f/ Nutrients (photosynthesis) • Kelp Forests marine life etc. Warmest Spot N. of Pt. Conception SATELLITE IMAGE -Cold Water (Purple)

  26. OUTLINE • World Ocean Circulation • Foundations of Physical Oceanography • Motion in the Ocean • Upwelling/Downwelling • BREAK • Patterns of Surface water Circulation • Patterns of Deep water Circulation • What Drives Deep water Circulation • Global Conveyer Belt

  27. Patterns of Surface water Circulation • Harald Sverdrop (1888-1957) • Early theoretical Understanding • Effects of a Boundary (continent) on Ocean Circulation • His Theories allowed for calculation of surface flows • via wind stress • In his Honor created … Water transport unit the “Sverdrup” = 1x106 m3 sec -1

  28. Patterns of Surface water Circulation • What does the Long-term averages of Surface H2O transport look like in terms of surface circulation?

  29. Western Boundary Currents • What are they and What do they arise from? • Currents located along the western sides of Ocean basins • Arise from an intensification of Gyre circulation • In response to variations in the Coriolis effect with lattitude Where are they Below? v

  30. Western Boundary Currents • All fast moving & narrower then most currents • e.g. in N. Atlantic - Gulf Stream (Most Famous) • ~2.3 m s-1 (Knots) • Transports Warm H2O from Gulf of Mexico to N. Atlantic Florida

  31. Western Boundary Currents • e.g. in N. Pacific – what Current? • Kuroshio ~ > 2.5 m s-1 (>5 Knots) ~ 2 miles sec! • Flow is complicated, Japan archipelago  wakes, eddies etc.

  32. Western Boundary Currents • e.g. in S. Atlantic – what Current? • Brazil Current ~ 2.2 m s-1 (<5 Knots) • Forms Highly Productive Large Marine Ecosystem (LME) • aka Patagonian Shelf

  33. Western Intensification • Challenge Question? • What is it - And what is it caused by? • Increase in flow rates of W. boundary currents caused by: • Coriolis effect which • Increases @ • Higher latitudes TAKE HOME Western Boundary Currents = Fast/ Narrow, b/c Coriolis What about Eastern Boundary Currents? Next slide. . .. CORIOLIS Force STRONGEST Stronger modest weak Gulf Stream or Kuroshio Latitude

  34. Eastern Boundary Currents – examples? • e.g. California Current • Slow moving (1 foot/ sec) • Bring cool water – coastal Upwelling  Moderate Climate • aka Mediterranean • Also produce considerable fog

  35. Equatorial Counter Currents • Weak seasonal currents ~ return some (warm) flow East • May play a role in Hurricane formation. . .

  36. Equatorial Counter Currents • Satellite imagery, warmer temp (yellow) Hurricane Alley

  37. Antarctic Circumpolar Current (ACC) • Only continuous current unimpeded by land masses • Important exchange pt for Waters or all three Oceans: • Atlantic, Pacific, Indian

  38. Summary • Warm & Cold Surface Water Currents

  39. OUTLINE • World Ocean Circulation • Foundations of Physical Oceanography • Motion in the Ocean • Upwelling/Downwelling • Patterns of Surface water Circulation • Patterns of Deep water Circulation • What Drives Deep water Circulation • Global Conveyer Belt

  40. Patterns of DEEP Water Circulation - T-S Diagrams • What are they and what are they used for? • Temp vs Salinity Diagrams: • mea. @ different pressures (depths) • Allow for the determination of diff. types of water masses & • How they are influencing mixing and current flow, their properties etc.. . . T-S Diagram Surface Ocean Deep Ocean

  41. Patterns of DEEP Water Circulation - T-S Diagrams

  42. Patterns of Deep water Circulation • Confirming your knowledge: • What is Needed to Form Deep Water? • Cold air/H2O temperatures, high salinity  (downward flux) • Colder/ salty water = dense • sinks • e.g. N. Atlantic • Gulf Stream transports • Warm/Salty H2O Greenland • S. of Greenland • Cold Air cools water • Cool/salty water sinks. . . • N.Atlantic deep water • aka (NADW)

  43. Patterns of Deep water Circulation • Ocean is Stratified (layered)- influenced by • Thermocline • Rapid change in temperature • Pycnocline • What is it? • Rapid change in density • (salinity & Temp) Influences the Major Water Masses . . .

  44. NOTES: • Saltier • More abundant • Influ deep circulation • Over greater region • Thought to confer greatest • Shut down of NADW • Abrupt climate changes Colder Most dense in World

  45. OUTLINE • World Ocean Circulation • Foundations of Physical Oceanography • Motion in the Ocean • Upwelling/Downwelling • Patterns of Surface water Circulation • Patterns of Deep water Circulation • What Drives Deep water Circulation • Global Conveyer Belt

  46. Deep water Circulation • Challenge Question – Current Philosophy • What Drives Deep water Circulation? • @ Highest latitudes (downward flux – sinking) • Density changes form (Cold & salty)  sinking H2O • @ lower Latitudes • Upward flux (upwelling) – does the WORK (pulling) upwelling

  47. Places where the seawater is cold enough and salty enough to form bottom water.

  48. OUTLINE • World Ocean Circulation • Foundations of Physical Oceanography • Motion in the Ocean • Upwelling/Downwelling • Patterns of Surface water Circulation • Patterns of Deep water Circulation • What Drives Deep water Circulation • Global Conveyer Belt

  49. All this Deep Water movement  • Global Conveyer Belt – • aka ThermoHaline Circulation • What is it? • Thermo (temp) & haline (salt) dependent circulation • Heat of Earth’s oceans dissipated from circulation process. .

  50. Global Ocean Conveyer Belt(ThermoHaline Circulation) • Wally Broecker’s Model – shows deep H2O formations + returns • Broecker et al., 1991, Oceanography • Challenge Question? • Where are the 2 major cites for DEEP water Formation? • N. Atlantic Deep Water (NADW) • Antarctic Bottom Water (AABW) NADW AABW

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