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| Titel |
Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model |
| VerfasserIn |
S. Dutkiewicz, A. E. Hickman, O. Jahn, W. W. Gregg, C. B. Mouw, M. J. Follows |
| 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 ; 12, no. 14 ; Nr. 12, no. 14 (2015-07-29), S.4447-4481 |
| Datensatznummer |
250118039
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| Publikation (Nr.) |
 copernicus.org/bg-12-4447-2015.pdf |
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| Zusammenfassung |
| We present a numerical model of the ocean that couples a three-stream
radiative transfer component with a marine biogeochemical–ecosystem component in
a dynamic three-dimensional physical framework. The radiative transfer
component resolves the penetration of spectral irradiance as it is absorbed and
scattered within the water column. We explicitly include the effect of several
optically important water constituents (different phytoplankton functional
types; detrital particles; and coloured dissolved organic matter, CDOM). The
model is evaluated against in situ-observed and satellite-derived products. In
particular we compare to concurrently measured biogeochemical, ecosystem, and
optical data along a meridional transect of the Atlantic Ocean. The simulation
captures the patterns and magnitudes of these data, and estimates surface
upwelling irradiance analogous to that observed by ocean colour satellite
instruments.
We find that incorporating the different optically important
constituents explicitly and including spectral irradiance was crucial to
capture the variability in the depth of the subsurface chlorophyll a (Chl a) maximum.
We conduct a series of sensitivity experiments to
demonstrate, globally, the relative importance of each of the water
constituents, as well as the crucial feedbacks between the light field,
the relative fitness of phytoplankton types, and the biogeochemistry
of the ocean.
CDOM has proportionally more importance at attenuating light at
short wavelengths and in more productive waters, phytoplankton absorption is
relatively more important at the subsurface Chl a
maximum, and water molecules have the greatest contribution
when concentrations of other constituents are low, such as in the
oligotrophic gyres. Scattering had less effect on attenuation,
but since it is important for the amount and type of upwelling irradiance, it is
crucial for setting sea surface reflectance.
Strikingly, sensitivity experiments in which
absorption by any of the optical constituents was increased led to
a decrease in the size of the oligotrophic regions of the subtropical
gyres: lateral nutrient supplies were enhanced as a result of
decreasing high-latitude productivity.
This new model that
captures bio-optical feedbacks will be important for improving our
understanding of the role of light and optical constituents on ocean
biogeochemistry, especially in a changing environment.
Further, resolving surface upwelling irradiance will make it easier to
connect to satellite-derived products in the
future. |
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