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CSIRO Marine and Atmospheric Research
Past Seminars

Seminar Abstract

Using sea level to understand El Nino

Previous studies have used warm water volume in the Pacific Ocean to predict ENSO with a seven month lead time. Warm water volume data however is only available back to 1980. Sea level shows a similar performance to warm water volume in predicting ENSO and now a reconstructed data set of sea level is available back to 1950 and earlier (Church and White et al. 2004).

Warm water volume is used to understand the recharge/discharge mechanism of ENSO (Meinen and McPhaden 2000). Sea level can be used in the same way. Studying this recharge/discharge mechanism back to 1950 in sea level shows that the formation of El Niño events altered around the time of the climate regime shift in 1975, when El Niño events became more intense. It appears that the recharge/discharge mechanism was less important during this earlier period and El Niño events began their development in the east of the basin rather than the central Pacific.

The question then is, has ENSO changed due to natural decadal or multidecadal variability, or has global warming changed the background state on which ENSO lies? If global warming is responsible for the change in ENSO, we may continue to see the intense El Niño events that have dominated the last twenty years.

We explore the reconstructed sea level data to try to shed light on these questions, comparing it with other data sets such as SST and windstress and comparing our results with SODA sea level and thermocline depths.

References:
Church, J. A., White, N. J., Coleman, R., Lambeck, K. and Mitrovica, J.X. 2004 'Estimates of the Regional Distribution of Sea Level Rise over the 1950-2000 Period.' Journal of Climate.17, 2609-2625.

Meinen, C.S. and McPhaden, M.J. 2000 'Observations of Warm Water Volume Changes in the Equatorial Pacific and Their Relationship to El Niño and La Niña.' Journal of Climate 13, 3551-3559.

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CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
Karen Wild-Allen, (Oceanographic seminars) CSIRO Marine and Atmospheric Research (03) 6232 5010
Piers Dunstan, (Biological seminars) CSIRO Marine Research (03) 6232 5382
Kerrie Bidwell, Antarctic Climate and Ecosystems CRC (03) 6226 2265 & IASOS, University of Tasmania (03) 6226 2509