The long term record of climate change

1. The long term record of climate change Or: 50 million years of climate change in 80 minutes

2. Controls on climate Tectonics Ocean circulation Orbital parameters

3. Oxygen isotopes have different controls on different time scales

4. The reasons for the isotopic change has 2 forcings colder More ice

5. Isotopes record broad climate change But why did it occur?..... Tectonics..

6. The Cretaceous world

7. Circulation in the Cretaceous was restricted at high latitudes

8. Ocean circulation in the early Tertiary

9. Eocene continental placement

10. Oligocene continental placement

11. In the Tertiary, the Southern Ocean began to open… The Cretaceous world comes apart. At the same time the Southern Ocean opens, the Atlantic began to open

12. Ocean circulation at 25 Ma

13. The reasons for this isotopic change has 2 forcings colder More ice

14. Earliest Miocene Circulation

15. Change in continental placement through the tertiary controls circulation and climate

16. The final piece • The isthmus of Panama closes at 3.3Ma • The basins are set (as today) • Northern hemisphere glaciation begins at ~2.4 Ma • Pulsing at ~40ka periodicity.

18. The broad brush misses lots of detail… colder More ice

19. Tectonic control orbital control Orbital parameters were always an influence– but as the basin shape is set up they become more influential. Also, we have a better record and can see the record of glacial pulsing in more detail. What are the orbital parameters?

20. Glacial cycles of the last 2 million years

21. Orbital changes cause changes in insolation • Insolation at different times of the year has different effects on global climate • The earth’s orbit varies in shape on long time scales. • These changes vary total insolation • And they vary seasonal insolation.

22. eccentricity Is the elliptical-ness of the orbit

23. The variation in eccentricity has a 19 and 100kyr period Eccentricity pattern through time

24. The variation of obliquity has a 40kyr period obliquity Is the tilt of the poles and it’s variation

25. Precession has a 20kyr periodicity Precession of the equinoxes

26. Sum total of the orbital control Gives us an added wave pattern that “resembles” the 18O record

27. Emerson and Hedges 2008 Climate record for the last 120ka  18O in the sediment record

28. Orbital parameters and climate are similar

29. Glacial cycles of the last 2 million years Past 2 million years shift from a 40k to 100k cyclicity

30. Climate and circulation feedback Past 300k – 3 cycles

31. Record of CO2 in the atmosphere The record of CO2 levels in the atmosphere has the same pattern as ice volume

32. Rapid climate change • Ocean circulation between glacial and interglacial modes • The triggers that can shift the circulation between modes can be rapid. • Modes can switch like a “switch”

33. The conveyor belt circulation And thermohaline circulation moves CO2 through the system…

34. Last glacial shutdown of NADW The polar front moved south. The location and character of NADW water formation changed

36. The NADW that formed was less in volume and shallower

37. The 13C reflects traces the concentration of CO2 in the deep ocean Curry and Oppo, 2005 Our tracer is 13C

38. NADW became NAIW Curry and Oppo, 2005 Our tracer is 13C

39. The biological pump interacts with the excess CO2 we are putting into the atmosphere. • The marine system is taking up CO2 in surface waters fixing it to organic carbon and carbonate and • Putting it into the deep ocean. • Because most of the deep ocean is “capped” by the thermocline, the respired CO2 remains there….. • If carbonate dissolves then the capacity of the water is increased (balanced by the alkalinity)

40. Water downwells: DIC enriched Low nutrients High O2 Controls on the fractionation of 13C 13C 13C 12C 13C 13C 12C 12C 13C 12C 13C 13C DIC (in Water) more depleted with increasing age 13C 12C 12C 12C 12C 12C Porewaters very sensitive to remineralization can be very depleted in 13C 12C 12C 12C 12C 12C 12C

41. Water downwells: Low nutrients High O2 low CO2 content Controls on the distribution of CO2 CO2 CO2 CO2 CO2 CO2 CO2 DIC DIC Corg DIC DIC Corg Corg DIC Corg DIC DIC content of Water increases with increasing age DIC DIC DIC Corg Corg Corg Carbonate Sediments are a source and sink of carbon, both Corg and CO2 Corg DIC Corg DIC Corg DIC

42. Moana Loa Vostok ice core Record of CO2 in the atmosphere through time Temperature records change in sync with carbon dioxide records

43. We now have all the pieces:Ocean controlled carbon cycling • There is a balance between atmosphere and ocean … • If ocean circulation is changed there is a moderately long-term effect on carbon cycling.

44. The CO2Climate connection How much CO2 in the ocean controls the levels in the atmosphere How fast the ocean circulates controls can change the amount of CO2 in the atmosphere (to change climate) The carbon cycle IS the climate cycle.

45. The carbon cycle summary

46. Two pumps put CO2 into the deep ocean

47. Changes in circulation affect the CCD In the glaciation the CCD rose about 1000m More dissolved CO2 stayed in the ocean and it came out of the atmosphere.

48. To reiterate….. The depth of the CCD shallowed in the LGM

49. Long term change in circulation has long term effects on CO2 cycling The CCD permanently dropped when deep circulation as we know it began after the Cretaceous (when the Atlantic opened). This “permanently” changed the oceans CO2 capacity

50. The “Wilson cycle” Are the very long term processes that affect CO2 and climate