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Satellite-based empirical models linking river plume dynamics with hypoxic area andvolume
Citation:
Le, C., J. Lehrter, C. Hu, AND D. Obenour. Satellite-based empirical models linking river plume dynamics with hypoxic area andvolume. GEOPHYSICAL RESEARCH LETTERS. American Geophysical Union, Washington, DC, 43(6):2693-2699, (2016).
Impact/Purpose:
We adapted a previously-developed color index (CI) approach to propose a river plume index (RPI) to detect Mississippi River plume dynamics and describe the relations between plume location and hypoxic area and volume. We then developed an empirical model to predict hypoxic area and volume.
Description:
Satellite-based empirical models explaining hypoxic area and volume variation were developed for the seasonally hypoxic (O2 < 2 mg L−1) northern Gulf of Mexico adjacent to the Mississippi River. Annual variations in midsummer hypoxic area and volume were related to Moderate Resolution Imaging Spectroradiometer-derived monthly estimates of river plume area (km2) and average, inner shelf chlorophyll a concentration (Chl a, mg m−3). River plume area in June was negatively related with midsummer hypoxic area (km2) and volume (km3), while July inner shelf Chl a was positively related to hypoxic area and volume. Multiple regression models using river plume area and Chl a as independent variables accounted for most of the variability in hypoxic area (R2 = 0.92) or volume (R2 = 0.89). These models explain more variation in hypoxic area than models using Mississippi River nutrient loads as independent variables. The results here also support a hypothesis that confinement of the river plume to the inner shelf is an important mechanism controlling hypoxia area and volume in this region.
