Assessing the spatial characteristics and temporal variabilities of the Mississippi and Atchafalaya River plumes

Document Type

Conference Proceeding

Publication Date

12-1-1992

Abstract

The Mississippi and Atchafalaya Rivers transport Mississippi River water into the northern Gulf of Mexico where the fluxes of freshwater, sediments and pollutants influence all aspects of shelf oceanography. In this paper, the Mississippi and Atchafalaya River plumes are investigated using satellite-derived information on turbidity during the `high' discharge spring of 1989 and the `low' discharge spring of 1992. The study focuses on relating plume size to variations in river discharge, wind events and stage of the tide in an attempt to better understand spatial and temporal changes in the distribution of riverine sediments in the northern Gulf of Mexico. Linear regression demonstrated that the two plumes respond very differently to river discharge changes. A strong positive relationship (R2 = 0.83) was found between Mississippi River discharge and the area of its plume. In contrast, a weak relationship (R2 = 0.29) was found between Atchafalaya River discharge and the area of its plume. The observed differences can be explained in terms of bathymetry of the receiving basin, wind events and the contribution of wind-wave resuspension to the plume. Whereas the Mississippi River plume consists mainly of newly discharged suspended sediments, the Atchafalaya River plume consists, in addition, of sediments resuspended within the bay and on the shallow shelf seaward of it. Wind speed, direction and fetch control the sites of resuspension, as well as the sediment transport pathways along and across the continental shelf. Strong westerly and northerly winds associated with winter frontal passages most efficiently resuspend (Atchafalaya case) and transport riverine sediments and pollutants across the shelf.

Publication Source (Journal or Book title)

Proceedings of SPIE the International Society for Optical Engineering

First Page

719

Last Page

728

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