1. Ocean Response to Global Warming William Curry Woods Hole Oceanographic Institution Wallace Stegner Center March 3, 2006

4. What is the Ocean’s Role in Climate? the ocean covers 70% of the earth ’ s surface the ocean covers 70% of the earth ’ s surface the ocean stores a thousand times more heat than the atmosphere the ocean stores a thousand times more heat than the atmosphere seawater stores four times more heat per unit mass than air seawater stores four times more heat per unit mass than air it transports 25 to 50% of the energy received from the sun it transports 25 to 50% of the energy received from the sun

5. What is the Ocean’s Role in Climate? it circulates slowly, on time scales of decades to centuries it circulates slowly, on time scales of decades to centuries it is the major source of heat to some regions like the North Atlantic it is the major source of heat to some regions like the North Atlantic it sets long-term patterns of atmospheric circulation affecting climate systems like ENSO, NAO it sets long-term patterns of atmospheric circulation affecting climate systems like ENSO, NAO

6. Equator to Pole Heat Transport

7. How will the Oceans Change as the Earth Warms? the oceans will warm, sea level will rise the oceans will warm, sea level will rise its salinity balance will be altered its salinity balance will be altered its ability to absorb CO 2 will change its ability to absorb CO 2 will change it will impact atmospheric circulation, storm tracks, severe storms, and the frequency and distribution of droughts it will impact atmospheric circulation, storm tracks, severe storms, and the frequency and distribution of droughts

8. Levitus et al., 2000 The oceans have been warming for the last 50 years

9. The net warming above 3000 m is 0.06 o C The oceans have absorbed about 30 times more heat than the atmosphere since 1955 Oceans18.2 x 10 22 J Atmosphere 6.6 x 10 21 J Indistinguishable from the expected response to rising CO 2 – an anthropogenic signal Levitus et al., 2001

10. The oceans will continue to absorb heat as the climate system warms Warming will cause sea water to expand The effect of ocean heat absorption will be to delay the warming of the atmosphere The rate and magnitude of global warming will be affected by how the ocean circulates in the future – when and where will it release the stored heat? What are the Implications?

11. What about Salinity? Oceans contain 97% of Earth’s water Oceans contain 97% of Earth’s water Oceans experience 86% of evaporation Oceans experience 86% of evaporation Oceans receive 78% of planetary precipitation Oceans receive 78% of planetary precipitation A 1% increase in Atlantic precipitation equals the annual Mississippi runoff A 1% increase in Atlantic precipitation equals the annual Mississippi runoff A key element of the global water cycle A key element of the global water cycle

12. The Water Cycle Will Accelerate With Global Warming A warmer atmosphere will carry more water vapor, because of the exponential increase of vapor pressure with temperature. A warmer atmosphere will carry more water vapor, because of the exponential increase of vapor pressure with temperature. An enhanced water cycle will change the distribution of salinity in the upper ocean. An enhanced water cycle will change the distribution of salinity in the upper ocean.

13. Sea surface salinity distributions are determined in large part by E-P patterns Global Salinity and E-P distributions Source: R.Schmitt,WHOI Source: HydroBase2

14. Increasing salinities in the tropical Atlantic

15. Over the same 40-year period, salinities have been increasing.. …. a shift in the entire Atlantic hydrological cycle? Ruth Curry et al., 2003 Surface Water

16. Tropical Salinities Increasing for last 40 years FresherSaltier Ruth Curry (pers. comm.) 1967-1972 1980-19841995-2000

17. Summer Arctic Sea Ice 1979 2003 NASA Goddard Space Flight Center

18. NY Times June 8, 2004 Greenland is melting

19. Curry and Mauritzen, in press Largest effects in the upper 1000 m

20. Freshwater storage and net flux anomalies Ruth Curry & Cecile Mauritzen, in press 19000 km 3 4000 km 3 15000 km 3 0.066 Sv 10,000 km 3

21. Large Scale Ocean Circulation

22. Fresher Deep Water Flowing South at 3000 m FresherSaltier Ruth Curry (pers. comm.) 1967-1972 1980-19841995-2000

23. Two Important Ocean Processes will be Affected Convection and thermohaline circulation – the large scale ocean circulation Air-sea coupling – El Nino and the North Atlantic Oscillation

24. Large-scale Ocean Circulation Affects the Heat Transport

25. Large Scale Ocean Circulation

26. Conveyor ON

27. Conveyor OFF

28. Manabe and Stouffer, 1997 Temperature Response Strong cooling in North Atlantic Warming everywhere else No net global change

29. Greenhouse models predict a slowdown in the deep water circulation IPCC Report

30. Summary The ocean and atmosphere work together to affect climate The ocean and atmosphere work together to affect climate Surface conditions of the ocean set atmospheric circulation – the surface conditions are changing Surface conditions of the ocean set atmospheric circulation – the surface conditions are changing Deep water produced in the Atlantic is exported to the world Deep water produced in the Atlantic is exported to the world The circulation system is density driven – warm, salty water becomes cold, dense, salty deep water The circulation system is density driven – warm, salty water becomes cold, dense, salty deep water The salinity balance appears to be changing The salinity balance appears to be changing

31. Summary Heat released to the atmosphere by the oceans is an important source of heat to the Atlantic region Heat released to the atmosphere by the oceans is an important source of heat to the Atlantic region Several models of future greenhouse climate produce a significantly altered Atlantic circulation Several models of future greenhouse climate produce a significantly altered Atlantic circulation Some of the changes predicted by the models may be occurring in the Atlantic today Some of the changes predicted by the models may be occurring in the Atlantic today

32. Air-Sea Interactions Ocean surface temperatures set atmospheric circulation

33. El Nino 1997-1998 January 1997 November 1997 Goddard Space Flight Center - NASA

35. High Phase Low Phase The North Atlantic Oscillation

36. High Index Low Index Fewer hurricanes More hurricanes

37. North Atlantic Oscillation Index

38. NAO and Gulf Stream Transport

39. The Gulf Stream South of Cape Cod

40. The Ocean and Climate Change Institute The Ocean and Climate Change Institute Woods Hole Oceanographic Institution