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The Value of Adding Optics to Ecosystem Models: a Case Study : Volume 4, Issue 3 (23/05/2007)

By Fujii, M.

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Book Id: WPLBN0003974674
Format Type: PDF Article :
File Size: Pages 47
Reproduction Date: 2015

Title: The Value of Adding Optics to Ecosystem Models: a Case Study : Volume 4, Issue 3 (23/05/2007)  
Author: Fujii, M.
Volume: Vol. 4, Issue 3
Language: English
Subject: Science, Biogeosciences, Discussions
Collections: Periodicals: Journal and Magazine Collection (Contemporary), Copernicus GmbH
Historic
Publication Date:
2007
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

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Chai, F., Boss, E., & Fujii, M. (2007). The Value of Adding Optics to Ecosystem Models: a Case Study : Volume 4, Issue 3 (23/05/2007). Retrieved from http://worldlibrary.net/


Description
Description: School of Marine Sciences, 5706 Aubert Hall, University of Maine, Orono, ME 04469-5706, USA. Many ecosystem models have been developed to study the ocean's biogeochemistry, but most of these models use simple formulations to describe light penetration and spectral quality. Given that processes such as photosynthesis and photo-oxidation are uniquely important for biogeochemical processes in the upper ocean, it is necessary to model light distribution accurately. In addition, the global scale observations of proxies of biogeochemical variables are based on the color of the ocean. The ability to simulate the color of the ocean provides the possibility of comparing model simulation with these observations. 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 field and subsurface light field 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. Results include large contributions by non-algal particles to the total scattering or attenuation (>50% at 660 nm) and their small contribution to particulate absorption (<20% at 440 nm), and a remarkable contribution by picoplankton to 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 is available, have to be constrained. Sensitivity analysis of the model results to optical parameters reveals the significant role of colored dissolved organic matter to the modeled properties. Coupling explicit optics to an ecosystem model provides several 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) added 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.

Summary
The value of adding optics to ecosystem models: a case study

Excerpt
Allali, K., Bricaud, A., and Claustre, H.: Spatial variations in the chlorophyll-specific absorption coefficients of phytoplankton and photosynthetically active pigments in the equatorial Pacific, J. Geophys. Res., 102(C6), 12 413–12 423, 1997.; Babin, M., Morel, A., Fournier-Sicre, V., Fell, F., and Stramski, D.: Light scattering properties of marine particles in coastal and open ocean waters as related to the particle mass concentration, Limnol. Oceanogr., 48(2), 843–859, 2003a.; Babin, M., Stramski, D., Ferrari, G. M., Claustre, H., Bricaud, A., Obolensky, G., and Hoepffner, N.: Variations in the light absorption coefficients of phytoplankton, nonalgal particles, and dissolved organic matter in coastal waters around Europe, J. Geophys. Res. 108(C7), 3211, doi:10.1029/2001JC000882, 2003b.; Barber, R. T., Sanderson, M. P., Lindley, S. T., Chai, F., Newton, J., Trees, C. C., Foley, D. G., and Chavez, F. P.: Primary productivity and its regulation in the equatorial Pacific during and following the 1991–1992 El NiÑo, Deep-Sea Res. Part II, 43(4–6), 933–969, 1996.; Behrenfeld, M. J. and Boss, E.: Beam attenuation and chlorophyll concentration as alternative optical indices of phytoplankton biomass, J. Mar. Res., 64, 431–451, 2006.; Behrenfeld, M. J. and Falkowski, P. G.: Photosynthetic rates derived from satellite-based chlorophyll concentration, Limnol. Oceanogr., 42, 1–20, 1997.; Behrenfeld, M. J., Boss, E., Siegel, D. A., and Shea, D. M.: Carbon-based ocean productivity and phytoplankton physiology from space, Global Biogeochem. Cycles, 19, GB1006, doi:10.1029/2004GB002299, 2005.; Bidigare, R. R. and Ondrusek, M. E.: Spatial and temporal variability of phytoplankton pigment distributions in the central equatorial Pacific Ocean, Deep-Sea Res. Part II, 43(4–6), 809–833, 1996.; Bishop, J. K. B.: Transmissometer measurement of POC, Deep-Sea Res. Part I, 46, 355–369, 1999.; Bissett, W. P., Carder, K. L., Walsh, J. J., and Dieterle, D. A.: Carbon cycling in the upper waters of the Sargasso Sea: II. Numerical simulation of apparent and inherent optical properties, Deep-Sea Res. Part I, 46, 271–317, 1999.; Boss, E. and Pegau, W. S.: The relationship of light scattering at an angle in the backward direction ot the backscattering coefficient, Appl. Opt., 40, 5503–5507, 2001.; Boss, E., Pegau, W. S., Lee, M., Twardowski, M. S., Shybanov, E., Korotaev, G., and Baratange, F.: The particulate backscattering ratio at LEO 15 and its use to study particles composition and distribution, J. Geophys. Res., 109(C1), C01014, doi:10.1029/2002JC001514, 2004.; Bricaud, A., Roesler, C. S., Parslow, J. S., and Ishizaka, J.: Bio-optical studies during the JGOFS-equatorial Pacific program: a contribution to the knowledge of the equatorial system, Deep-Sea Res. Part II, 49, 2583–2599, 2002.; Chai, F., Dugdale, R. C., Peng, T.-H., Wilkerson, F. P., and Barber, R. T.: One-dimensional ecosystem model of the equatorial Pacific upwelling system. Part I: model development and silicon and nitrogen cycle, Deep-Sea Res. Part II, 49, 2713–2745., 2002.; Chai, F., Barber, R. T., and Lindley, S. T.: Origin and maintenance of high nutrient condition in the equatorial Pacific, Deep-Sea Res. Part II, 42(4–6), 1031–1064, 1996.; Chavez, F. P.: Size distribution of phytoplankton in the central and eastern tropical Pacific, Global Biogeochem. Cycles, 3, 27–35, 1989.; Chavez, F. P., Buck, K. R., Coale, K. H., Martin, J. H., DiTullio, G. R., Welshmeyer, N. A., Jacobson, A. C., and Barber, R. T.: Growth rates, grazing, sinking and iron limitation of equatorial Pacific phytoplankton, Limnol. Oceanogr., 36, 1816–1833, 1991.; Cho, B. C. and Azam, F.: Biogeochemical significance of bacterial biomass in the ocean's euphotic zone, Mar. Ecol. Prog. Ser., 63, 253–259, 1990.; Chung, S. P.

 

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