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Observation of Different Phytoplankton Groups and Biomass Using Differential Optical Absorption Spectroscopy on SCIAMACHY Data and Comparisons to in-situ, Global Model and MERIS algal-1 Data

Astrid Bracher(1), Bettina Schmitt(1), John Burrows(2), Marco Vountas(2), Tilman Dinter(2), Rüdiger Röttgers(3), Steffen Gehnke(3) and Ilka Peeken(4)

(1) Alfred-Wegener-Institute of Polar and Marine Research, Bussestr. 24, 27570 Bremerhaven, Germany
(2) University Bremen - Inst of Environmental Physics, Otto-Hahn-Allee 1, 28359 Bremerhaven, Germany
(3) GKSS - Institute of Coastal Research, Max-Planck-Str., 21502 Geesthacht, Germany
(4) IFM-Geomar, Düstenbrooker Weg 20, 24105 Kiel, Germany

Abstract

In order to understand the marine phytoplankton’s role in the global marine ecosystem and biogeochemical cycles it is necessary to derive global information on the distribution of major functional phytoplankton types (PFT) in the world oceans. In our study we use instead of the common ocean color sensors such as CZCS, SeaWiFS, MODIS, MERIS, with rather low spectral resolution, the Differential Optical Absorption Spectroscopy (DOAS) to study the retrieval of phytoplankton distribution and absorption with the satellite sensor Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). SCIAMACHY measures back scattered solar radiation in the UV-Vis-NIR spectral region with a high spectral resolution (0.2 to 1.5 nm). We used in-situ measured phytoplankton absorption spectra from two different RV Polarstern expeditions where different phytoplankton groups were representing or dominating the phytoplankton composition in order to identify these characteristic absorption spectra in SCIAMACHY data in the range of 430 to 500 nm. In addition also SCIAMACHY data were analysed with DOAS in the range of 530 to 590 where absorption from cyanobacterial photosynthetic pigment phycoerythrin was identified. Our results show clearly these phytoplankton assemblage absorptions in the SCIAMACHY data. The conversion of these differential absorptions by including the information of the light penetration depth (according to Vountas et al., Ocean Science, 2007) leads to globally distributed concentrations for these characteristic phytoplankton groups, but also for a well mixed phytoplankton assemblage (corresponding to ocean chl a). Phytoplankton concentrations have been determined for three monthly periods (Feb-March 2004, Oct-Nov 2005 and Oct-Nov 2007).The information retrieved by DOAS from SCIAMACHY on phytoplankton groups and chl a is compared to collocated in-situ measurements, MERIS data (chl a only) and to the global model analysis with the NASA Ocean Biogeochemical Model (NOBM from http://reason.gsfc.nasa.gov/OPS/Giovanni/) according to Gregg and Casey 2006 and Gregg 2006. Results are of great importance for global modelling of marine ecosystem and climate change studies regarding changes in the ocean.

 

Workshop presentation

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry