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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

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  1. Volcanic eruptions: their impact on sea level and oceanic heat content John A. Church1,2*, Neil J. White1,2 and Julie M. Arblaster3,4 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 Title slide 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 Mt Pinatubo 1991 El Chichon 1982

  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 20thC ensembles: 1890-1999 4 members each with the following forcings: V volcanic S solar G ghg Su sulfates Oz ozone SOz solar+ozone VS volcanic+solar VSOz volcanic+solar+ozone GS ghg+sulfates GOz ghg+ozone GSuOz ghg+sulfates+ozone SGSuOz solar+ghg+sulfates+ozone VSGSuOz volcanic+solar+ghg+sulfates+ozone (ALL)

  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 1022 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)

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

  22. 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 1022 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

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