Effects of parameter indeterminacy in pelagic biogeochemical modules of Earth System Models on projections into a warming future: The scale of the problem.

Löptien, Ulrike and Dietze, Heiner (2017) Effects of parameter indeterminacy in pelagic biogeochemical modules of Earth System Models on projections into a warming future: The scale of the problem. Open Access Global Biogeochemical Cycles, 31 (7). pp. 1155-1172. DOI 10.1002/2017GB005690.

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Abstract

Numerical Earth System Models are generic tools used to extrapolate present climate conditions into a warming future and to explore geoengineering options. Most of the current-generation models feature a simple pelagic biogeochemical model component that is embedded into a three-dimensional ocean general circulation model. The dynamics of these biogeochemical model components is essentially controlled by so-called model parameters most of which are poorly known. Here we explore the feasibility to estimate these parameters in a full-fledged three-dimensional Earth System Model by minimizing the misfit to noisy observations. The focus is on parameter identifiability. Based on earlier studies, we illustrate problems in determining a unique estimate of those parameters that prescribe the limiting effect of nutrient- and light-depleted conditions on carbon assimilation by autotrophic phytoplankton. Our results showcase that for typical models and evaluation metrics no meaningful “best” unique parameter set exists. We find very different parameter sets which are, on the one hand, equally consistent with our (synthetic) historical observations while, on the other hand, they propose strikingly differing projections into a warming climate.

Document Type: Article
Keywords: biogeochemical ocean modeling; model verification and validation; parameter estimation; future projections; uncertainty; Earth System Model
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
OceanRep > SFB 754
OceanRep > SFB 754 > A1
OceanRep > SFB 754 > A2
OceanRep > SFB 754 > B9
OceanRep > SFB 754 > B1
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1002/2017GB005690
ISSN: 0886-6236
Related URLs:
Projects: SFB754, PalMod
Date Deposited: 16 Aug 2017 09:43
Last Modified: 01 Feb 2018 07:08
URI: http://oceanrep.geomar.de/id/eprint/39122

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