Title: Aggressive space mapping for optimisation of a marine ecosystem model

Authors: M. Prieß T. Slawig

Addresses: Department of Computer Science, Algorithmic Optimal Control – CO₂ Uptake of the Ocean, Excellence Cluster The Future Ocean, Christian-Albrechts-Platz 4, 24118 Kiel, Germany. ' Department of Computer Science, Algorithmic Optimal Control – CO₂ Uptake of the Ocean, Excellence Cluster The Future Ocean, Christian-Albrechts-Platz 4, 24118 Kiel, Germany

Abstract: We apply the aggressive space mapping (ASM) algorithm to parameter optimisation of a one-dimensional marine ecosystem model. Such models are important to calculate the global carbon cycle and specifically the oceanic CO₂ uptake. The aim of the optimisation is to find model parameters that minimise the misfit between model output and observational data. ASM first solves for an optimum of a computationally cheaper low-fidelity model that in our case is based on a coarser time discretisation while still guaranteeing numerical stability. Secondly, an approximate optimum of the high-fidelity model is iteratively found by a parameter mapping applying a Quasi-Newton method and Broyden update. The applicability of the ASM technique to the problem is verified by using synthetic target data. Results are compared to those of the direct high-fidelity model optimisation. We show that a very reasonable solution can be obtained while yielding a significant reduction in the total optimisation cost.

Keywords: marine ecosystem models; surrogate-based optimisation; low-fidelity model; aggressive space mapping; ASM; globalised quasi-Newton; numerical optimisation; inverse problems; ecosystem modelling; global carbon cycle; ocean carbon uptake; CO2; carbon dioxide.

DOI: 10.1504/IJMMNO.2012.044732

International Journal of Mathematical Modelling and Numerical Optimisation, 2012 Vol.3 No.1/2, pp.98 - 116

Published online: 20 Aug 2014 *

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