Fine-sediment transport associated with cold-front passages on the shallow shelf,Gulf of Mexico |
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| Institution: | 1. Institute of Oceanology, Chinese Academy of Sciences, Nanhai Road, 7, 266071 Qingdao, China;2. Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Nanhai Road, 7, 266071 Qingdao, China;3. University of Chinese Academy of Sciences, Yuquan Road, 19A, 100049 Beijing, China;4. North China Sea Marine Forecasting center of State Oceanic Administration, Yunling Road, 27, 266061 Qingdao, China;5. Laboratory for Ocean and Climate Dynamics, Qingdao National Laboratory for Marine Science and Technology, Wenhai Road, 1, 266237 Qingdao, China;1. University of Antwerp, Ecosystem Management Research Group, Universiteitsplein 1-c, B-2610 Antwerp, Belgium;2. Göttingen University, Institute of Geography, Cartography, GIS and Remote Sensing Section, Goldschmidtstraße 5, 37077 Göttingen, Germany;3. Flanders Hydraulics Research (FHR), Berchemlei 115, 2140 Antwerp, Belgium;4. Research Institute for Nature and Forest (INBO), Havenlaan 88, 1000 Brussels, Belgium;5. Royal Netherlands Institute for Sea Research (NIOZ), Korringaweg 7, 4401 NT Yerseke, Netherlands;1. Key Laboratory of Submarine Geosciences and Technology, MOE, Ocean University of China, Qingdao 266100, China;2. Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China;3. Key Laboratory of Marine Hydrocarbon Resources and Environment Geology, China Geological Survey, Ministry of Land and Resources, Qingdao Institute of Marine Geology, Qingdao 266071, China;4. Laboratory for Ocean & Coast Geology, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China |
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| Abstract: | The eastern part of the chenier plain of the Louisiana coast has been prograding seaward over the last few decades while much of the rest of the Louisiana coast is experiencing high erosion rates. The source of sediment is the Atchafalaya River, which has been delivering sediment to the coastal ocean since the 1940s. Researchers have suggested that the repeated passage of cold fronts during winter and early spring plays an important role in delivering sediment to the coast. A sediment-transport study on the Atchafalaya coast was conducted between October 1997 and March 2001, which included several field experiments in early March, the period of high discharge from the Atchafalaya and frequent cold-front activity. A combination of shipboard profiling and time-series measurements from a bottom tripod and array of wave sensors on the inner shelf has resulted in a data set that illustrates the mechanism of onshore transport. For a cold-front passage sampled in 2001, during pre-front conditions, sediment is resuspended and mixed throughout the water column, with transport rates onshore and to the west of 53 and 184 g s?1 m?1, respectively. Post-front conditions also result in onshore transport due to onshore flow (upwelling) in the lower meter of the water column and formation of a high-concentration bottom layer. Post-front onshore transport rates are 32 g s?1 m?1 and most of the transport occurs in the bottom meter of the water column. The repeated cycling of cold-front passages leads to a positive feedback with transport onshore during both pre- and post-front conditions, and effective attenuation of wave energy over the muddy inner shelf inhibits erosion at the coast. Thus, the chenier-plain coast is experiencing high progradation rates (up to 29 m yr?1), while most of the Gulf coast is eroding. |
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