SPECIAL DATES: MPA meeting…6 Jul R/V Pt Sur Cruise…14 Jul R/V Pt Sur Cruise…25 Jul

1. SPECIAL DATES: MPA meeting…6 Jul R/V Pt Sur Cruise…14 Jul R/V Pt Sur Cruise…25 Jul Exam-1 (definite)...2 Aug Exam-2 (Tentative)…1 Sep Labor Day Holiday...5 Sep Final Exam...19 Sep (Sp-226, 1300-1450) OC3230 Calendar, Summer 2005version 7 August 2005 EX 1 S.D. trip

2. Distributions of properties (“Taxonomy” of T-S) T: 0-6 ˚C S: 34-35 ‰ Tave: 3.5 ˚C Save: 34.7 ‰ Mostly “zonal” but with important variations Vert. Grad >> Horz. Grad Presentation types: Horizontal maps or plan views (contours) Vertical Profiles Vertical Sections (contours) 75% byvolume

3. “Summer”(N.H.) “Winter”(N.H.)

4. Annual range is maximum in mid latitudes

5. (Zonal) Sea Surface T, , S T follows the sun  follows 1/T S follows ? ?

6. (Zonal) Sea Surface Salinity

7. Sea Surface Salinity (cm)

8. Sea Surface Salinity “Fresh” “Salty”

9. Temperature Profiles thermocline Salinity halocline

10. Profiles

11. Density Profiles pycnocline Note how curves join at depth: Deep water conditions are less variable Top-to-bottom contrast is most extreme at the equator

12. Profiles and Contours Seasonal cycle of upper ocean temperature in mid latitudes Note: different methods of displaying the same data 50˚N, 145˚W(“Station P”)

13. Sections-Temperature (Vertical) Temperature section through Atlantic Ocean Note bowl-shaped isotherms Note iso-thermal (constant temperature) conditions at high latitudes, particularly in the southern hemisphere

14. Sections-Temperature ? ? Which profile comes from which latitude?

15. Sections-Temperature A review: Which section is in situ temperature and which section ispotential temperature, ?

16. Sections-Temperature & Salinity ? Salty Fresh

17. Sections-Temperature & Salinity T (˚C) Atlantic S (‰) version from text (note opposite view from west)

18. Sections-Temperature & Salinity T (˚C) Pacific S-min S-min S (‰)

19. Sections-Oxygen (ml/l) “Young” Atlantic Surface values are ~8 ml/l Pacific “Old”

20. Sections-WOCE (80s-90s) The World Ocean Circulation Experiment (WOCE) Decade-long, major international program to map T-S (and other) properties Section A-16 along 25W Longitude provides a good look at the water mass structure of the Atlantic Ocean

21. Sections-WOCE (80s-90s) Potential Temperature

22. Sections-WOCE (80s-90s) Salinity

23. Sections-WOCE (80s-90s) Oxygen

24. Other Tracers Known Source Functions OC Distributions Chlorofluorocarbons (e.g., Freon) and their ratios

25. Other Tracers Today’s CFC distributions in the Atlantic Ocean Note the high values in the northeast surface waters consistent with a deep-water source region

26. Other Tracers Helium and “Bomb” carbon or heavy water (tritium)

27. Water Masses What’s going on? Interleaving and mixing of “water masses” created near the surface in particular areas Deepest layers originate from far N and S in Atlantic

28. Water Masses Step 1: Subduction N-S surface gradient verticalgradient Step 2: Mixing as water flows along isopycnals…

29. Water Masses Water formed as a mixture of two water types must have T-S values that fall along the line between the two original points Water Type: point on theT-S diagram Water Mass: line on theT-S diagram T S

30. Water Masses Water formed as a mixture of three water types must have T-S values that fall within the triangle be-tween the original points Water Type: point on theT-S diagram T S

31. Water Masses ***Critical Figure*** This illustrates changes in the shape of profiles and T-S curves as mixing occurs between distinct water types The example mimics the low-salinity layer observed at mid depths in the Atlantic T S T-S

32. Water Masses Thermohaline Circulation is Inferred fromT-S Distributions

33. Water Masses

34. Water Masses ***Critical*** Classic T-S curve observed in the S. Atlantic Ocean It provides evidence of 4 different source water types T S AAIW: Antarctic Intermediate Water NADW: North Atlantic Deep Water AABW: Antarctic Bottom Water

35. T S Water Masses (< 4˚C) World Ocean ? ? ?

36. T S Water Masses (< 4˚C) World Ocean Indian Pacific Atlantic

37. Water Masses Deep water masses originate from the Southern Ocean around Antarctica or from the north Atlantic Ocean.

38. Water Masses Intermediate waters are dominated by AAIW, which originates along the subpolar front in the Southern Ocean

39. Water Masses

40. Water Masses Value and depth of the salinity minimum layers in the Atlantic Ocean Evidence for northward spreading of AAIW with a concentration of flow along the western boundary ? AAIW

41. Water Masses Surface water masses are many and have T-S characteristics of the region

42. Water Masses Mediterranean Outflow

43. Thermohaline “Conveyor Belt” Thermohalinecirculationinfluencesand buffersthe climatesystemthrough theslow circula-tion of thedeep currentsand theexchange between surface and deep water that takes place over several thousand years

44. Thermohaline “Conveyor Belt”

45. Thermohaline “Conveyor Belt”

46. O.T.E.C. closed system open system concept system