A comparison of satellite and cruise chlorophyll-a measurements in the Scotia Sea, Antarctica

We compared both SeaWiFS (Sea-viewing Wide Field-of-View Sensor) and MODIS (Moderate-resolution Imaging Spectroradiometer) chlorophyll-a (chl-a) measurements with simultaneous ship based data obtained during a 2003 British Antarctic Survey (BAS) research cruise. This cruise provided in situ data from a large area of the Scotia Sea containing areas of extreme contrasts in terms of chl-a concentration. We present the results of correlation analysis between the in situ ship based chl-a measurements and the satellite chl-a products (SeaWiFS, and from MODIS the semi-analytic, SeaWiFS analog OC3M, HPLC empirical algorithms). The results confirm the good correlation between SeaWiFS and in situ chl-a measurements. The results indicate Terra MODIS chl-a measurements show reduced correlation to in situ values when compared to SeaWiFS. In addition, we compared chl-a averages from the various algorithms, over wider geographical regions of greater ecological relevance than point measurements. Over an area of 3° × 3°, SeaWiFS estimates could be as much as 2 times higher than estimates from MODIS.