SGER: Seabed and Geochemical Deltaic Changes Induced by Hurricane Katrina

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ABSTRACTOCE-0553064With funding from this Small Grant for Exploratory Research, researchers at the East Carolina University will assess the impact of Hurricane Katrina on sediment redistribution in the offshore Mississippi River delta region. The passage of this powerful hurricane directly over the birdfoot delta of the Mississippi River on 29 August 2005 offers a unique opportunity to evaluate the sediment disturbance and deposition/export associated with a very large meteorological event. Recent results from rapid-response research following Hurricane Ivan indicate that across- and off-shelf transport associated with major hurricanes is enormous. Also, pipeline damage associated with Hurricane Ivan revealed that mass movement may be an important transport agent during these events.Over the previous 24 months, the research team had collected a time series of cores on the shelf and in the canyon adjacent to the Mississippi delta in order to understand the short-term sediment dynamics. Based on this work and research by others, they hypothesize that major weather events, e.g. hurricanes, have a disproportionately important role in the destabilization and redistribution of sediments and associated biogeochemically-important constituents on the Mississippi margin, particularly via mass movements. They plan to reoccupy 11 stations on the Mississippi margin that were in the immediate path of Hurricane Katrina as a category 5 hurricane. Geochemical, radiochemical and sedimentological analyses of sediment cores will be conducted. X-radiography also will be used to document structural changes. A geophysical survey will put geochemical, radiochemical and sedimentological observations into a spatial context and will help develop a more accurate conceptual framework of the nature of sediment transport in response to this event. By responding rapidly to this major event and through close collaborations with colleagues at Oregon State University and Tulane University), the research team expects to provide quantitative estimates of the cross-shelf transport and deposition of materials following Hurricane Katrina. In terms of broader impacts, this project addresses fundamental issues of the role major storms play in the dispersal of sediments in coastal systems. The disturbance of the sea bed may enhance sediment reworking processes, and therefore have a direct influence on diagenetic reactions that occur in the sediments and on the composition of the buried material, as well as nutrient and oxygen availability in overlying waters. The results of this study should also provide a better understanding of the dynamics and history of particles within river-dominated shelf environments. The timing, duration, and nature of this project offer an excellent opportunity to expose several upper-level undergraduate and graduate students to science at sea. Through communication with faculty, efforts will be made to involve students at Tulane University and University of New Orleans. Additionally, research insights and observations will be incorporated into a web site (funded separately by an existing NSF grant) aimed at educating the public on the source-to-sink transfer of sediment and solutes.