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

Received: 08 May 2021
Accepted: 12 May 2021

Published online: 04 Jan 2012 *

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