Parameter optimisations of a marine ecosystem model in the Southern Ocean
The Southern Ocean plays a central role in global biological production (Sarmiento et al., 2004). Quantifying the mechanisms that regulate magnitude and variability in plankton biomass in the Southern Ocean is a key challenge in understanding controls on global climate (Busalacchi, 2004). Numerical...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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UNSW, Sydney
2010
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| Online Access: | http://hdl.handle.net/1959.4/50411 https://unsworks.unsw.edu.au/bitstreams/423937e9-dc40-42bc-918b-44d961a668f5/download https://doi.org/10.26190/unsworks/23571 |
| Summary: | The Southern Ocean plays a central role in global biological production (Sarmiento et al., 2004). Quantifying the mechanisms that regulate magnitude and variability in plankton biomass in the Southern Ocean is a key challenge in understanding controls on global climate (Busalacchi, 2004). Numerical models are an integral means of understanding large scale views of seasonal plankton cycles (Fasham et al., 1990). Marine biogeochemical models are characterised by non-linear dynamics and the annual model trajectories are highly sensitive to the parameters used to run them. Experiments were performed to select a stochastic inverse method to objectively estimate the parameters of a simple four component nitrogen based mixed-layer marine ecosystem model for the Southern Ocean. Twin experiments using the Metropolis-Hastings algorithm and simulated annealing show that simulated annealing holds promise as a standard means of assigning the parameters of marine biogeochemical models in a way that improves the model agreement to available observations. SeaWiFS surface chlorophyll estimates in the Sub-Antarctic Zone show low concentrations south west of Tasmania and high concentrations south east of Tasmania. Simulated annealing was used to estimate the model parameters at two locations in the Sub-Antartic Zone (station P1 at , and station P3 at , ) through assimilation of SeaWiFS chlorophyll observations. Model parameter estimates were compared to in situ parameter estimates from the SAZ-Sense (Sub-Antarctic Zone Sensitivity to environmental change) project stations P1 and P3 in the austral summer of 2007. The parameter estimates suggest that different ecosystems are present within the Sub-Antarctic Zone. Station P3 has higher regenerated production with an f-ratio of 0.57 compared to P1 which has an f-ratio of 0.70, indicating larger size fractionated phytoplankton at P1 with a greater capability to sink and smaller size fractioned organisms at P3 with greater recycling ability. Different biological processes rather than ... |
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