Hobart

Seminar Abstract

Friday 4 July 2008, 11.30am (Tas time)
CSIRO Auditorium, Hobart

Catia M Domingues
Postdoctoral Fellow
CSIRO Marine and Atmospheric Research

Improved estimates of upper-ocean warming and multi-decadal sea-level rise

Catia M. Domingues¹, John A. Church ^1,2, Neil J. White1,², Peter J. Gleckler³, Susan E. Wijffels¹, Paul M. Barker¹ and Jeff R. Dunn¹

Changes in the climate system’s energy budget are predominantly revealed in ocean temperatures and the associated thermal expansion contribution to sea-level rise. However, climate models do not reproduce the large decadal variability in globally-averaged ocean heat content inferred from the sparse hydrographic data set, even when volcanic and other variable climate forcings are included. Also, the sum of the observed contributions to sea-level rise has not adequately explained the historical rise. Here, we report improved estimates of near-global ocean heat content and thermal expansion for the upper 700 m of the ocean for 1950 to 2003, using a reconstruction method that allows for sparse data coverage and applying recent corrections to reduce systematic errors in the most common ocean temperature observations. Our linear trend in ocean heat content (thermal expansion) corresponds to an air-sea flux of 0.36 ± 0.06 W m⁻² (0.52 ± 0.08 mm yr⁻¹) for 1961 to 2003, and 0.35 ± 0.26 W m⁻² (0.79 ± 0.36 mm yr⁻¹) for 1993 to 2003, over the ocean surface area considered (3.3 x 10¹⁴m²). Compared to earlier estimates, our rates are about 50% larger for the historical period but about 40% smaller for the recent period, consistent with the recognition that previously estimated rates for the 1990s were biased high by instrumental errors. On average, the decadal variability of the climate models with volcanic forcing now agrees approximately with the observations but the multi-decadal trends are smaller than observed. We add our observational estimates of upper ocean thermal expansion to other contributions to sea-level rise and find that the sum of contributions from 1961 to 2003 is about 1.5 ± 0.4 mm yr⁻¹, in good agreement with our updated estimate of near-global mean sea level of 1.6 ± 0.2 mm yr⁻¹.

¹Centre for Australian Weather and Climate Research, CSIRO Marine and Atmospheric Research, GPO Box 1538, Hobart, Tasmania 7001, Australia.

²Antarctic Climate and Ecosystems Cooperative Research Centre, Hobart, Private Bag 80, Tasmania 7001, Australia.

³Program for Climate Model Diagnosis and Intercomparison, Lawrence Livermore National Laboratory, Mail Code L-103, 7000 East Avenue, Livermore, California 94550, USA.

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Location:
CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
To schedule a seminar, contact:
Bernadette Sloyan, (Oceanographic seminars) CSIRO Marine and Atmospheric Research (03) 6232 5152
Thomas Kunz, (Biological seminars) CSIRO Marine and Atmospheric Research
(03) 6232 5076
Natalie Dowling, (Fisheries Modelling) CSIRO Marine and Atmospheric Research
(03) 6232 5148
Jillian Enraght-Moony, (seminar administrator) CSIRO Marine and Atmospheric Research (03) 6232 5320
Communications Manager, Antarctic Climate and Ecosystems CRC (03) 6226 2265
Margaret Hazelwood, Institute of Antarctic and Southern Ocean Studies (IASOS) University of Tasmania (03) 6226 2971

Last updated 21/07/09