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| Titel |
A mechanistic particle flux model applied to the oceanic phosphorus cycle |
| VerfasserIn |
T. DeVries, J.-H. Liang, C. Deutsch |
| 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 ; 11, no. 19 ; Nr. 11, no. 19 (2014-10-07), S.5381-5398 |
| Datensatznummer |
250117624
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| Publikation (Nr.) |
 copernicus.org/bg-11-5381-2014.pdf |
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| Zusammenfassung |
| The sinking and decomposition of particulate organic matter are critical
processes in the ocean's biological pump, but are poorly understood and
crudely represented in biogeochemical models. Here we present a mechanistic
particle remineralization and sinking model (PRiSM) that solves the evolution
of the particle size distribution with depth. The model can represent a wide
range of particle flux profiles, depending on the surface particle size
distribution, the relationships between particle size, mass and sinking velocity, and
the rate of particle mass loss during decomposition. The particle flux model
is embedded in a data-constrained ocean circulation and biogeochemical model
with a simple P cycle. Surface particle size distributions are derived from
satellite remote sensing, and the remaining uncertain parameters governing
particle dynamics are tuned to achieve an optimal fit to the global
distribution of phosphate. The resolution of spatially variable particle
sizes has a significant effect on modeled organic matter production rates,
increasing production in oligotrophic regions and decreasing production in
eutrophic regions compared to a model that assumes spatially uniform particle
sizes and sinking speeds. The mechanistic particle model can reproduce global
nutrient distributions better than, and sediment trap fluxes as well as,
other commonly used empirical formulas. However, these two independent data
constraints cannot be simultaneously matched in a closed P budget commonly
assumed in ocean models. Through a systematic addition of model processes, we
show that the apparent discrepancy between particle flux and nutrient data
can be resolved through P burial, but only if that burial is associated with
a slowly decaying component of organic matter such as might be achieved
through protection by ballast minerals. Moreover, the model solution that
best matches both data sets requires a larger rate of P burial (and
compensating inputs) than have been previously estimated. Our results imply
a marine P inventory with a residence time of a few thousand years, similar to
that of the dynamic N cycle. |
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