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| Titel |
The value of adding optics to ecosystem models: a case study |
| VerfasserIn |
M. Fujii, E. Boss, F. Chai |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 4, no. 5 ; Nr. 4, no. 5 (2007-10-11), S.817-835 |
| Datensatznummer |
250001964
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| Publikation (Nr.) |
 copernicus.org/bg-4-817-2007.pdf |
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| Zusammenfassung |
| Many ecosystem models have been developed to study the ocean's
biogeochemical properties, but most of these models use simple formulations
to describe light penetration and spectral quality. Here, an optical model
is coupled with a previously published ecosystem model that explicitly
represents two phytoplankton (picoplankton and diatoms) and two zooplankton
functional groups, as well as multiple nutrients and detritus. Surface ocean
color fields and subsurface light fields are calculated by coupling the
ecosystem model with an optical model that relates biogeochemical standing
stocks with inherent optical properties (absorption, scattering); this
provides input to a commercially available radiative transfer model
(Ecolight). We apply this bio-optical model to the equatorial Pacific
upwelling region, and find the model to be capable of reproducing many
measured optical properties and key biogeochemical processes in this region.
Our model results suggest that non-algal particles largely contribute to the
total scattering or attenuation (>50% at 660 nm) but have a much smaller
contribution to particulate absorption (<20% at 440 nm), while
picoplankton dominate the total phytoplankton absorption (>95% at
440 nm). These results are consistent with the field observations. In order
to achieve such good agreement between data and model results, however, key
model parameters, for which no field data are available, have to be
constrained. Sensitivity analysis of the model results to optical parameters
reveals a significant role played by colored dissolved organic matter
through its influence on the quantity and quality of the ambient light.
Coupling explicit optics to an ecosystem model provides advantages in
generating: (1) a more accurate subsurface light-field, which is important
for light sensitive biogeochemical processes such as photosynthesis and
photo-oxidation, (2) additional constraints on model parameters that help to
reduce uncertainties in ecosystem model simulations, and (3) model output
which is comparable to basic remotely-sensed properties. In addition, the
coupling of biogeochemical models and optics paves the road for future
assimilation of ocean color and in-situ measured optical properties into the
models. |
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