Seasonal and Inter-Annual Variations of Remotely Sensed Biogeochemical Parameters in Northern Gulf of Mexico and Their Correlations to the Size of Hypoxia

English Abstract:

With the development of algorithms for many biogeochemical parameters in surface water, satellite remote sensing has become a useful tool for the study of marine ecosystems. The hypoxia (O₂ < 2 mol L^-1) in the northern Gulf of Mexico has been measured annually in summer for about three decades with shipboard methods. A systematic study of other biogeochemical parameters and their relation with dissolved oxygen and systematic monitoring of the hypoxia size are essential for understanding hypoxia development and for evaluating the effectiveness of the proposed conservation remedies. Here, we report a study of seasonal and inter-annual variations of remotely-sensed area-weight-mean of sea surface chlorophyll a (chl a), colored dissolved organic matter (CDOM) index, particulate organic carbon (POC), particulate inorganic carbon (PIC), and attenuation coefficient at 490 nm (K₄₉₀) of the northern Gulf of Mexico. Area-weight-mean of chl a, CDOM index, POC, PIC, and K₄₉₀ were derived from SeaWiFS data from September 1997 to December 2010. Each one of these biogeochemical parameters showed a strong seasonal cycle with a peak in the Spring and a valley in Autumn. In addition, a strong linear correlation between hypoxia size in bottom waters and area-weighted-mean of chl a, POC, and K₄₉₀ in surface waters were observed. These correlations offer an alternative method for estimating hypoxia size from remote sensing data.