Publication Date:
2022-05-26
Description:
© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geoscientific Model Development 9 (2016): 1827-1851, doi:10.5194/gmd-9-1827-2016.
Description:
During the fifth phase of the Coupled Model Intercomparison Project (CMIP5) substantial efforts were made to systematically assess the skill of Earth system models. One goal was to check how realistically representative marine biogeochemical tracer distributions could be reproduced by models. In routine assessments model historical hindcasts were compared with available modern biogeochemical observations. However, these assessments considered neither how close modeled biogeochemical reservoirs were to equilibrium nor the sensitivity of model performance to initial conditions or to the spin-up protocols. Here, we explore how the large diversity in spin-up protocols used for marine biogeochemistry in CMIP5 Earth system models (ESMs) contributes to model-to-model differences in the simulated fields. We take advantage of a 500-year spin-up simulation of IPSL-CM5A-LR to quantify the influence of the spin-up protocol on model ability to reproduce relevant data fields. Amplification of biases in selected biogeochemical fields (O2, NO3, Alk-DIC) is assessed as a function of spin-up duration. We demonstrate that a relationship between spin-up duration and assessment metrics emerges from our model results and holds when confronted with a larger ensemble of CMIP5 models. This shows that drift has implications for performance assessment in addition to possibly aliasing estimates of climate change impact. Our study suggests that differences in spin-up protocols could explain a substantial part of model disparities, constituting a source of model-to-model uncertainty. This requires more attention in future model intercomparison exercises in order to provide quantitatively more correct ESM results on marine biogeochemistry and carbon cycle feedbacks.
Description:
This work was supported by H2020 project CRESCENDO
“Coordinated Research in Earth Systems and Climate: Experiments,
kNowledge, Dissemination and Outreach”, which received
funding from the European Union’s Horizon 2020 research and
innovation programme under grant agreement no. 641816 and by
the EU FP7 project CARBOCHANGE “Changes in carbon uptake
and emissions by oceans in a changing climate” which received
funding from the European community’s Seventh Framework Programme
under grant agreement no. 264879. Jerry Tjiputra acknowledges ORGANIC project (239965/F20)
funded by the Research Council of Norway. Christoph Heinze
and Jerry Tjiputra are grateful for support through project EVA –
Earth system modelling of climate variations in the Anthropocene
(229771/E10) funded by the Research Council of Norway, as well
as CPU-time and mass storage provided through NOTUR project
NN2345K as well as NorStore project NS2345K. Keith Lindsay
and Scott C. Doney acknowledge support from the National
Science Foundation.
Repository Name:
Woods Hole Open Access Server
Type:
Article
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