A New Algorithm for Calculating Productivity from Ocean Color Derived Chlorophyll-a
John
Marra, Lamont-Doherty Earth Observatory, marra@ldeo.columbia.edu
(Presenting)
John
O'reilly, NOAA, jay.o'reilly@noaa.gov
Kimberly
Hyde, NOAA, kimberly.hyde@noaa.gov
We investigate the use of a new model, Ocean Productivity from Absorption and Light (OPAL) in calculating primary productivity from ocean color. (2003). The OPAL model generates profiles of chlorophyll estimated from the SeaWiFS chlorophyll using the algorithm from the literature and uses the absorption properties in the water column to vertically resolve estimates of light attenuation in approximately 100 strata within the euphotic zone. Absorption by pure water is assumed to be a constant value over PAR wavelengths; chlorophyll-specific phytoplankton absorption is parameterized empirically; absorption by photosynthetic pigments is distinguished from total absorption; and absorption by colored dissolved organic matter (CDOM) is calculated based on the idea that upwelled water will have a high CDOM, which then becomes photo-oxidized with time near the surface. The chlorophyll-specific phytoplankton absorption is used to calculate productivity, while absorption by pigments, water, and CDOM are used to vertically resolve light attenuation. SST, which is used as a proxy for seasonal changes in the phytoplankton community, is related to the chlorophyll-specific absorption coefficient. The quantum efficiency is obtained from a hyperbolic tangent and a constant φmax. The model is tested using in situ productivity data from our database. A global map of productivity will be shown.
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