1. Our water planet and our water hemisphere

2. Role of the ocean in climate
Main roles:
Storage and transport of heat
Storage and transport of CO2
Production of Cloud Condensation Nuclei
Other potentially important roles:
Methane hydrate release
Production of N2O
Ocean/ice sheet interactions

4. Temperature
N-S Section
Atlantic
N-S Section
Pacific

6. Salinity
N-S Section
Atlantic
N-S Section
Pacific

7. Observed meridional heat transports
Trenberth and Caron (2001) J. Clim.

8. Upper ocean circulation

9. A snapshot of surface temperature distribution
in the western North Atlantic

10. A representation of ocean thermohaline circulation

11. Detailed meridional overturning circulation

12. Deep current observations at 30 S off Chile

13. Meridional flow at 30 S in the Chile Basin
Deep poleward
boundary current,
 10 Sv
Deep equatorward
Flow,  3 Sv east of the East Pacific Rise
AAIW flow in the western Chile Basin
Shaffer et al. (2005), Deep Sea Research

14. Atlantic overturning circulation

15. THC influence on climate (1): Zonal temperature deviations

17. THC influence on climate (2): Surface temperature changes after a THC shutdown

18. Global distribution of recent temperature trends
Temperatura
Global distribution of recent temperature trends
                                                                                                                        
IPCC-2001

19. What drives the thermohaline circulation?

20. Opening and evolution of Drake Passage over the past 40 million years

21. High latitude Southern Hemisphere currents

22. Meridional flows and water mass transformations
around Antarctica

23. THC sensitivity to mixing and Southern Ocean winds in a GCM

24. Model THC changes for future global warming (quadrupling of CO2 in 140 years)
Gregory et al. (2005), GRL

25. THC hysteresis in coupled climate models
Rahmstorf et. al. (2005), GRL, 32, L23605

26. Ice core and ocean sediment records of 18O
Millennial-scale cycles are also evident in high-resolution, ocean sediment data
Intermediate depth, 18O decreases can preliminarily be interpreted as warming during cold conditions in Greenland
Heinrich events always start during cold conditions in Greenland and result in significant surface layer freshening.
Greenland
Antarctic
Surface
1020 m
heinrich events
3148 m

27. Our low order climate model
Ocean:
High vertical resolution
Frictional model for N-S flow
Stability-dependent vertical diffusion
”Horizontal gyre” mixing
Southern Ocean shelf water formation and Ekman transport
Drake Passage effect
Atmosphere:
Seasonal and orbital forcing
Energy and moisture transports
Oxygen isotopic composition of
moisture
Ice/snow:
Variable sea ice/snow cover
Prescribed ice cap extents

28. Model Holocene and LGM overturning circulations
Holocene (0 kyr BP)
LGM (22 kyr BP)

29. Model millennial-scale climate oscillations
Key features:
Abrupt onset of overturning and convection after gradual intensification.
Abrupt shutdown after gradual weakening.
Alternating NADW and AABW dominance in the deep ocean with AABW confined below 2000 m.

30. Subsurface 18Oc changes reflect mainly temperature changes
Ocean temperature changes over the oscillations
Strong warming occurs at intermediate depths during the cold phase of the oscillation
This warming is due to lack of cooling from North Atlantic deep convection to oppose diffusive warming at low latitudes
Subsurface 18Oc changes reflect mainly temperature changes

31. Last glacial period simulation
Time dependent forcing:
Insolation
Ice cap extent
Atmospheric CO2
Wind stress
6 kyr Heinrich event cycle
Key features:
Oscillations for intermediate glacial conditions.
Surface/intermediate depth calcite 18O vary out of phase with Greenland temp.
Deep ocean calcite 18O and Antarctic temp vary in phase with symmetric shape.
40o-90oN
40o-90oS
Surface
1000 m
3000 m

32. Yearly mean solar insolation difference between 40S-40N and 40N-90N