Using shortened spin‐ups to speed up ocean biogeochemical model optimization

Oliver, S.; Khatiwala, S.; Cartis, C.; Ward, Ben; Kriest, Iris. 2024 Using shortened spin‐ups to speed up ocean biogeochemical model optimization. Journal of Advances in Modeling Earth Systems, 16 (9). 10.1029/2023ms003941

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Official URL: http://dx.doi.org/10.1029/2023ms003941

Abstract/Summary

The performance of global ocean biogeochemical models can be quantified as the misfit between modeled tracer distributions and observations, which is sought to be minimized during parameter optimization. These models are computationally expensive due to the long spin-up time required to reach equilibrium, and therefore optimization is often laborious. To reduce the required computational time, we investigate whether optimization of a biogeochemical model with shorter spin-ups provides the same optimized parameters as one with a full-length, equilibrated spin-up over several millennia. We use the global ocean biogeochemical model MOPS with a range of lengths of model spin-up and calibrate the model against synthetic observations derived from previous model runs using a derivative-free optimization algorithm (DFO-LS). When initiating the biogeochemical model with tracer distributions that differ from the synthetic observations used for calibration, a minimum spin-up length of 2,000 years was required for successful optimization due to certain parameters which influence the transport of matter from the surface to the deeper ocean, where timescales are longer. However, preliminary results indicate that successful optimization may occur with an even shorter spin-up by a judicious choice of initial condition, here the synthetic observations used for calibration, suggesting a fruitful avenue for future research.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1029/2023ms003941
ISSN:	1942-2466
Date made live:	19 Sep 2024 16:25 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/538047

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1029/2023ms003941

ISSN:

1942-2466

Date made live:

19 Sep 2024 16:25 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/538047