Hobart

Seminar abstract

Tuesday 30 October 2007, 11.30am (Tas time)
CSIRO Auditorium, Hobart

Jim Gunson
Hadley Centre for Climate Change
Met Office, UK

Ocean biogeochemical modelling for climate change studies

An overview of recent developments and ongoing research in modelling ocean biogeochemistry for earth system models at the Hadley Centre. The CLAW hypothesis asserts that production of dimethylsulphide (DMS) by ocean phytoplankton can form part of a feedback on global climate. The sea-air DMS flux over the open ocean is a source of aerosols for cloud formation, which can affect the amount of radiation reaching the ocean, and hence the planktonic production of DMS. Results from sensitivity experiments using a coupled ocean-atmosphere climate model (HadCM3) show a small negative feedback with regional variations. The latest climate model in development at the Hadley Centre is HadGEM2-ES, an earth system model with fully interactive atmosphere, ocean and terrestrial sub-models. New parametrizations of DMS production by phytoplankton are implemented. The importance of iron limitation of phytoplankton growth has led to the implementation of the Diat-HadOCC model in HadGEM2-ES. The marine ecosystem can respond to changes in atmospheric dust deposition associated with climate change, allowing other feedbacks to operate onto climate sensitivity through air-sea exchanges of carbon and dimethyl sulphide. An important element of air-sea gas exchange is the parameterization of the piston velocity. There is currently wide uncertainty in the size of gas flux estimates at high wind speeds. The inclusion of a sea-state dependence in the flux calculation is demonstrated. Existing marine ecosystem models can have a wide range of complexity. Some model intercomparison projects are underway to allow the evaluation and assessment of marine ecosystem models. Some ways forward are presented.

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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:
Karen Wild-Allen, (Oceanographic seminars) CSIRO Marine and Atmospheric Research (03) 6232 5010
Thomas Kunz, (Biological seminars) CSIRO Marine and Atmospheric Research
(03) 6232 5076
Jillian Enraght-Moony (seminar administrator) CSIRO Marine and Atmospheric Research (03) 6232 5456
Sandra Zicus, Antarctic Climate and Ecosystems CRC (03) 6226 7888
Margaret Hazelwood, Institute of Antarctic and Southern Ocean Studies (IASOS) University of Tasmania (03) 6226 2971

Last updated 21/12/07