In:
Biogeosciences, Copernicus GmbH, Vol. 17, No. 12 ( 2020-06-18), p. 3057-3082
Abstract:
Abstract. Global biogeochemical ocean models are often tuned to match the
observed distributions and fluxes of inorganic and organic
quantities. This tuning is typically carried out “by hand”. However,
this rather subjective approach might not yield the best
fit to observations, is closely linked to the circulation employed
and is thus influenced by its specific features and even its faults. We here investigate the
effect of model tuning, via objective optimisation, of one biogeochemical
model of intermediate complexity when simulated in five
different offline circulations.
For each circulation, three of six model parameters have
been adjusted to characteristic features of the respective circulation. The values
of these three parameters – namely, the oxygen utilisation of
remineralisation, the particle flux parameter and potential nitrogen
fixation rate – correlate significantly with deep mixing and ideal age of
North Atlantic Deep Water (NADW) and the outcrop area of Antarctic
Intermediate Waters (AAIW) and Subantarctic Mode
Water (SAMW) in the Southern Ocean. The
clear relationship between these parameters and circulation
characteristics, which can be easily diagnosed from global models, can
provide guidance when tuning global biogeochemistry within any new
circulation model. The results from 20 global cross-validation experiments show that parameter sets
optimised for a specific circulation can be transferred between
similar circulations without losing too much of the model's fit to
observed quantities. When compared to model intercomparisons of
subjectively tuned, global coupled biogeochemistry–circulation models, each with different circulation
and/or biogeochemistry, our results show a much lower
range of oxygen inventory, oxygen minimum zone (OMZ) volume and
global biogeochemical fluxes.
Export production depends to a large extent
on the circulation applied, while deep particle flux is mostly determined
by the particle flux
parameter. Oxygen inventory, OMZ volume, primary
production and fixed-nitrogen turnover depend more or less equally on both factors,
with OMZ volume showing the highest sensitivity, and residual variability.
These results show a beneficial effect of
optimisation, even when a biogeochemical model is first optimised in
a relatively coarse circulation and then transferred to a different finer-resolution
circulation model.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-17-3057-2020
DOI:
10.5194/bg-17-3057-2020-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2020
detail.hit.zdb_id:
2158181-2
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