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Surface Water & Deep Water CIRCULATION

Surface Water & Deep Water CIRCULATION. 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.

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Surface Water & Deep Water CIRCULATION

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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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