Bio-optical relationships and ocean color algorithms for the north polar region of the Atlantic
[1] Up to now, relatively few bio-optical measurements have been made in the high northern latitude waters, which allow sound relationships for ocean color remote sensing to be determined. We collected optical and chlorophyll a concentration, Chl, data in the north polar region of the Atlantic in su...
| Main Authors: | , , , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1062.1609 http://www.iopan.gda.pl/%7Estramska/Stramska_papers_pdf/Stramska_et_al_JGR_2003.pdf |
| Summary: | [1] Up to now, relatively few bio-optical measurements have been made in the high northern latitude waters, which allow sound relationships for ocean color remote sensing to be determined. We collected optical and chlorophyll a concentration, Chl, data in the north polar region of the Atlantic in summer season. The investigated region includes subarctic and arctic waters between 70°N and 80°N within the meridional zone between 1°E and 20°E. Our measurements show that the current NASA global algorithms, OC2, OC4, and chlor-MODIS, generally overpredict Chl in the investigated waters by a factor of about 2 at low pigment concentrations (<0.2 mg m À3 ) and underpredict Chl at higher concentrations (20-50% at 2-3 mg m À3 ). For our data set, the best two-band algorithm for Chl involves the ratio of remote-sensing reflectance, R rs (442)/R rs (555), at 442-nm and 555-nm light wavebands. We found that the general trend of variation in the blue-to-green reflectance ratio, R rs (442)/R rs (555) or R rs (490)/R rs (555), with Chl was driven primarily by Chldependent change in the green-to-blue ratio of absorption by pure seawater and particles. The effect of the blue-to-green backscattering ratio was of secondary importance. We observed a characteristic optical differentiation of waters within the investigated region. The majority of waters, which are here hypothesized to be dominated by diatoms, exhibited a relatively high blue-to-green reflectance ratio. The waters at several other stations, presumably dominated by dinoflagellates and/or prymnesiophytes, showed much lower reflectance ratio. Our data also show that the seemingly random variations in particulate absorption and backscattering coefficients at any given Chl are significant (more than a factor of 2) in the investigated waters. |
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