Optical Constituents Along A River Mouth and Inlet: Variability And Signature In Remotely Sensed Reflectance

River mouths are an environment where the variability in water color is most varied and complex. This complexity exists in both time and space. Variability in river flow, dissolved and particulate composition of the river, variability in ocean constituents forced by light, wind and tides, and variability in the interaction of these two end members result in large concentration changes and their characteristics within and around a river mouth in both space and time (e.g. Doxaran et al., 2009).

The color of the water in such environments is influenced by dissolved organic material coming with the river, sediments from both river and resuspended by winds and waves and phytoplankton, which find both nutrients and high-light in the stratified water of the river plume. Since different physical processes (e.g. river flow, wind) affect differently the concentration of the different material in the water (e.g. through advection, dilution, resuspension), traditional algorithms designed to retrieve optical constituents from the water’s color fail when applied to such areas (e.g. Green et al., 2008).

The goals of this project are:

1. Measure the variability of optical properties in-space along a river mouth/inlet and observe the variability in time at a single position over a tidal cycle.
2. Relate this variability to the concentration and dynamics of dissolved and particulate materials, including variability in the particulate size distribution.
3. Relate the optical properties to the ocean reflectance so that algorithm to invert surface color to in-water constituents can be tested and improved.

References

Doxaran D., J.M. Froidefond, P. Castaing and M. Babin, 2009. Dynamics of the turbidity maximum zone in a macrotidal estuary (the Gironde, France): Observations from field and MODIS satellite data. Estuarine, Coastal and Shelf Science 81, 321–332.

Green, R. E., R. W. Gould, and D. S. Ko, 2008: Statistical models for sediment/detritus and dissolved absorption coefficients in coastal waters of the northern Gulf of Mexico. Continental Shelf Research, doi:10.1016/j.csr.2008.02.019.