QUIZ 2, PARTS 1 & 2 Open Wed, Sept 30 th !

1. QUIZ 2, PARTS 1 & 2 Open Wed, Sept 30th! IS THIS YOU? The quiz will be open for 12 hours 3 pm Wednesday to 3 am Thursday Go to either “Quizzes” from the homepageOR “Assessments” on the left panel. 1888AD3D 1C7AC6A0 1697BF3E 1741EDBB 071D0913 06AAFE52 Reminder: we’re counting your top 3 marks from 5 quizzes (Read the syllabus for details!) REGISTER YOUR CLICKER!!!!!!

2. Hydrosphere IV: Deep water circulation, climate links Goals for Today • DESCRIBE the general pattern and time scale of density-driven, deep water circulation on Earth today. • EXPLAIN how deep ocean circulation helps modulate Earth’s climate. • PREDICT how deep water circulation might change if the positions of continents changed.

3. RELEVANCE Heat transport Nutrient & carbon cycling Movie plots(The Day After Tomorrow)

4. Controls on salinity:River input Ganges-Brahmaputra Amazon

5. Controls on salinity: • Evaporation and precipitationIncrease or decrease sea surface salinity • Ice formation and meltingIncrease or decrease sea surface salinity • River inputDecrease sea surface salinity • Mixing within the oceanChange distribution of salt (surface and at depth)

6. What BEST EXPLAINS the “End of Summer” salinity profile for the Labrador Sea? Clicker Q: • High rainfall, lots of wind mixing • Low rainfall, low wind mixing • Ice melt, lots of wind mixing • Ice formation, low wind mixing • Ice melt, low wind mixing End of summer Fall Early winter Winter

7. Seasonal evolution: Labrador Sea End of summer Fall Early winter Winter

8. Seawater  Distribution in Surface Water

9. NADW: Major Driver of Deep Ocean Circulation surface flow deep flow

10. Seawater  Distribution in Surface Water Weddell Sea

11. Antarctic Bottom Water formation:

12. Major sites of deep water formation North Atlantic Weddell Sea

13. X X Model of global thermohaline circulation Atlantic Indian Pacific

14. Western Intensification at Depth

15. Clicker Question: Where would we find the “oldest” deep water (the water that’s been down there for the longest time) C B A D E

16. How fast does it go? Evidence from bomb tests

17. Tritium distribution In the North Atlantic, 1973 Full cycle  ~ 1000 years

18. Oldest deep water?

19. Evidence from Nutrients

20. Evidence from Dissolved oxygen

21. Clicker Question: Where would you expect the concentration of CARBON in deep water to be the HIGHEST? C B A D E

22. The future?North Atlanticsurface wateris gettingFRESHER Salinity Salinity data from differentsites in the North Atlantic Dickson et al., 2002 1964 2002

23. Weaker Gulf Stream during last ice age? Marshak, Fig. 18.9

24. Deep Ocean Circulation:one pathway for heat in Earth’s climate system

25. Influence of the Solid Earth What if…the Drake Passage were closed? LAND!

26. Influence of the Solid Earth What if…the Panama Isthmus were OPEN? Water!

27. Influence of the Solid Earth AABW blocked by Walvis Ridge

28. Summary: Thermohaline Circulation • Surface water gets dense enough to sink in two major regions – the North Atlantic and around Antarctica. This sinking water is the start of the “ocean conveyor belt”, which describes water circulation through the deep ocean basins. On average, the deep ocean circulation takes about 1000 years for a full cycle. • Deep ocean circulation transports heat, just like the atmosphere and surface ocean, but on a different time scale. It also interacts with surface currents to influence global and regional climate. • The position of continents changes over time. The opening or closing of passageways can have major effects on ocean circulation (and thus heat transport) Relevance: nutrients, heat transport, movie plots

29. DISCUSSION BOARD Questions • (Groups 13, 14 & 15) What if the central American Isthmus were gone and the Atlantic and Pacific Oceans were connected at those latitudes. How might thermohaline circulation patterns change? • (Groups 16, 17 & 18) What effect might a reduction in the rate of formation of NADW have on the surface circulation in the North Atlantic in general, and why might this have consequences for the climate of northwest Europe?

30. In preparation for next lecture… ****

31. On an index card…what if…the central American isthmus were gone and the Atlantic and Pacific Oceans were connected at those latitudes? How might thermohaline circulation patterns change? Why? Groups of 3-4:Discussion leader: best-looking shoes. 30ºN 30ºN 0º 0º 30ºS 30ºS GONE! Topliss, et al., 2002 SEA SURFACE SALINITY

32. Gulf Stream Warm Core Ring

33. Gulf Stream Ring formation Warm rings north intocolder water Cold rings south intowarmer water

34. G3

35. Extra slides below this one

36. Role of Oceans in Global Heat Transport

37. Summary: thermohaline circulation • Changes in density (controlled by T and S) drive deep and intermediate ocean circulation. • Water masses acquire T and S characteristics primarily at the surface, and change those characteristics through mixing. • Deep water formation occurs in the North Atlantic and the Southern Ocean (cold, salty). • The “Conveyor Belt” is much slower than surface circulation (~1000 yrs/cycle). • Thermohaline circulation is closely connected to Earth’s climate.

38. A possible DB question would be to ask what would the diagram on slide 9 look like without heat transport by atmosphere and ocean and ask them to calculate the temperature of the equator and the poles. This could be a good wrap up question at the end of the ocean lectures From Roger

39. Cool SST animations athttp://svs.gsfc.nasa.gov/vis/a000000/a003300/a003389/index.html

40. Why is there noPacific Ocean Deep Water? Low salinity water cannot sink!

41. Global Warming, the Thermohaline Circulation and Climate Change High latitude water salinity decreases Global warming More ice melting Less warm surface water pushed to high latitude Weakens or stop sinking of high latitude water A possible mechanism by which Global Warming could shut down the Thermohaline Circulation! High latitude water density decreases Weakens or shuts down thermohaline circulation Europe and Canada may get even cooler weather!

42. Conveyor from Open U.

43. Theoretical Circulation at depth

44. Does deep water form in the Pacific?

45. T and S in Atlantic, Pacific and Indian Oceans

46. Post the slides below as a separate file, after Friday morning the 26th

47. Controlled by winds and the position of land masses and mountain ranges: • NE Trades pick up moisture in the Atlantic, carries it across the Isthmus of Panama (too small to act as a barrier)  moist warm air reaches the ITCZ in the Eastern equatorial Pacific where it ascends and looses its moisture into the Pacific…. • NE Trades are not able to transport water vapor from Indian to Atlantic because Africa acts as a barrier… Sea Surface Salinity  Due to a transfer of water vapor from Atlantic to Pacific

48. H • Controlled by winds and the position of land masses and mountain ranges: • The Westerlies pick up moisture in the N. Atlantic and quickly carry it into the North Pacific, bypassing most of the Eurasian continent in winter, because of the presence of high pressure cell in the middle of the continent that pushes the Westerlies to the North.

49. If the Westerlies were to cross Eurasia, they would loose most of their moisture before reaching the Pacific and much of it would be returned to the Atlantic by European and Arctic rivers H The winter high pressure cell forces the Westerlies further north, resulting in a shorter path from the N. Atlantic to the N. Pacific, thereby allowing much of the moisture picked up in the N. Atlantic to reach the N. Pacific North Atlantic North Pole North Pacific

50. H • Controlled by winds and the position of land masses and mountain ranges: • There is little transport of water vapor from the N. Pacific to the N. Atlantic, because the western mountain ranges of N. America act as an efficient “orographic” barrier that returns most precipitation to the Pacific