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CSIRO Marine and Atmospheric Research
Past Seminars

Seminar Abstract

Oxygen: a reliable tracer of large-scale biological productivity in the oceans?

Climate change experiments have predicted a 15% reduction of biological productivity in the oceans over the next century. But, we do not know how to measure these changes yet. Two observational techniques, based on seasonal oxygen variability, have potential. One technique uses air-sea oxygen fluxes and the other uses atmospheric O2/N2 concentrations. But, in the southern hemisphere oceans, current estimates of new production based on the atmospheric technique are almost a factor of three times higher than estimates based on the oceanic technique.

We apply both techniques to simulated oxygen fields in the southern hemisphere. We evaluate how effectively the techniques retrieve simulated new production, and demonstrate that the new production estimates are biased by physical oxygen fluxes; particularly by oxygen fluxes driven by the ventilation of the Southern Ocean. Estimates based on atmospheric O2/N2 are more biased by ventilation oxygen fluxes than those based on air-sea oxygen fluxes. Consequently, the atmospheric technique greatly overestimates new production. However, the atmospheric technique lends itself better to monitoring long-term changes in biological productivity. For seasonal oxygen variability to be a reliable tracer of new production, we need to estimate the magnitude of the bias introduced by the ventilation oxygen flux and be confident that the long-term variability of the ventilation oxygen flux is small.

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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