1. Title slide Volcanic eruptions: their impact on sea level and oceanic heat content John A. Church 1,2 *, Neil J. White 1,2 and Julie M. Arblaster 3,4 1 CSIRO Marine Research, GPO Box 1538, Hobart Tasmania. 7001. Australia. 2 ACE CRC, Hobart, Tasmania, Australia 3 National Center for Atmospheric Research, Boulder, Colorado, USA 4 Bureau of Meteorology Research Centre, Melbourne, Victoria, Australia Mt Pinatubo eruption in the Philippines, June 15, 1991. Gases and solids injected 20 km into the stratosphere.

2. Reconstructed global average sea level for the period 1950 to 2000 Agung 1963 El Chichon 1982 Mt Pinatubo 1991

3. Radiative forcing of climate From Ramswamy et al., 2001, IPCC TAR

4. Peaks of -5 W m -2 following major explosive volcanic eruptions From Ramswamy et al., 2001, IPCC TAR

5. Different stratospheric loading models

6. PCM 20 th C ensembles: 1890-1999 Vvolcanic Ssolar Gghg Susulfates Ozozone SOzsolar+ozone VSvolcanic+solar VSOzvolcanic+solar+ozone GSghg+sulfates GOzghg+ozone GSuOzghg+sulfates+ozone SGSuOzsolar+ghg+sulfates+ozone VSGSuOzvolcanic+solar+ghg+sulfates+ozone (ALL) 4 members each with the following forcings: DOE/NCAR Parallel Climate Model AtmosphereCCM3 T42 18L ~ 2.8 degree LandLSM OceanPOP 32L ~2/3 degree Sea-iceDynamic and thermodynamic

7. Observed concentrations and loadings used to force the model

8. Simulated GMSL with/without volcanic forcing 1890-2000

9. Differences in GMSL between simulations with/without volcanic forcing1890-2000

10. Volcanic forcing results in a rapid fall in GMSL of ~5 mm

11. Differences in global ocean heat content between simulations with/without volcanic forcing1890-2000

12. Volcanic forcing results in a fall in global average heat content of ~3 x 10 22 J

13. Much of the heat content changes in the upper 200 m but some deeper signals

14. Can we detect the signal in observations? In models can –Isolate forcing –Use ensembles to average variability Observations –many signals –natural variability –Inadequate observations Implies may be difficult to detect signal

15. Differences in global ocean heat content between simulations with/without volcanic forcing1960-2000

16. Modelled and observed ocean heat content changes are correlated but the observed signal is larger.

17. Differences in GMSL between simulations with/without volcanic forcing 1960-2000

18. Modelled and observed GMSL changes are correlated but the observed signal is larger.

19. What are the mechanisms involved? Examine Pinatubo response in the model –Best agreement with observations –Best observations Look at global ocean heat budgets Ensemble averages

20. Surface ocean heat fluxes for the Pinatubo eruption (1991)

23. Differences in GMSL between simulations with/without volcanic forcing for the Pinatubo eruption

24. Differences in GMSL between simulations with/without volcanic forcing and Levitus’ steric heights for the Pinatubo eruption

25. Differences in global ocean heat content between simulations with/without volcanic forcing for the Pinatubo eruption

26. Differences in global ocean heat content between simulations with/without volcanic forcing and Levitus’ heat content for the Pinatubo eruption

27. Conclusions Large heat content variations –order 3 x 10 22 J in models, same order but smaller than previous controversial estimates of ocean heat content variability Sea level falls of order 5 mm (potentially larger) following volcanic eruptions Evaporation changes – same order as interannual variations in global land precipitation Small deceleration of heat-content increase and sea-level rise Post Pinatubo recovery in sea level occurs during modern satellite record Longer term impacts (deeper signals) T/S signals in ocean and their impact

28. Title slide Mt Pinatubo eruption in the Philippines, June 15, 1991. Gases and solids injected 20 km into the stratosphere.

29. Reconstructed global average sea level for the period 1950 to 2000