Use of Satellite Remote Sensing Measurements to Improve Hypoxia Prediction on the Louisiana Continental Shelf

Abstract:

Recurrence of extensive hypoxia on the Louisiana shelf during the summer has strong impacts to the marine life and ecosystems. The formation of hypoxia depends on nutrient enhanced primary production and subsequent respiration in the water and sediment. It also depends on the physical processes of vertical stratification, transport, mixing and air-sea exchanges. All these processes are spatially and temporally variable. A high resolution coastal circulation model that covers the Louisiana shelf, therefore, has been developed for realistic simulation to better understand the processes of hypoxia formation in the region. Multi-year model simulation has been conducted driven by NOGAPS/COAMPS surface fluxes. The result shows that the stratification predicted by the model is too weak to produce realistic bottom hypoxia applying a Simple Dissolved Oxygen scheme. The weak stratification is partly due to overheating in shallow water resulting from excessive solar penetration by applying a constant water type. It is also partly due to unrealistic surface salinity flux based on seasonal climatology. To improve upon these known biases, the light attenuation estimated from SeaWiFS/MODIS and rainfall estimated from TRMM have been used. The predicted temperature and in particular the salinity using the satellite data were improved in comparison to observations and the stratification over the shelf is substantially improved resulting in realistic simulation of bottom-water hypoxia.