Geologic control on the evolution of the inner shelf morphology offshore of the Mississippi barrier islands, northern Gulf of Mexico, USA

Flocks, James G.; Kindinger, Jack L.; Kelso, Kyle W.

doi:10.1016/j.csr.2015.04.008

Cited by 10 publications

(2 citation statements)

References 43 publications

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“…These effects can occur on various length and time scales through both the effects of offshore bathymetric features on wave‐ and current‐induced flow patterns in the nearshore and also possible cross‐shore exchange of sediment between the nearshore and the inner‐shelf. Examples of where the geologic framework is strongly varying spatially are the inner shelves of Mississippi (Flocks et al, ), West Florida (Finkl et al, ), South Carolina (Denny et al, ), Delmarva Peninsula (Pendleton et al, ), and New York (Schwab et al, ). Such inner‐shelf areas have rarely been mapped in high resolution.…”

Section: Introductionmentioning

confidence: 99%

Persistent Shoreline Shape Induced From Offshore Geologic Framework: Effects of Shoreface Connected Ridges

et al. 2017

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Mechanisms relating offshore geologic framework to shoreline evolution are determined through geologic investigations, oceanographic deployments, and numerical modeling. Analysis of shoreline positions from the past 50 years along Fire Island, New York, a 50 km long barrier island, demonstrates a persistent undulating shape along the western half of the island. The shelf offshore of these persistent undulations is characterized with shoreface‐connected sand ridges (SFCR) of a similar alongshore length scale, leading to a hypothesis that the ridges control the shoreline shape through the modification of flow. To evaluate this, a hydrodynamic model was configured to start with the US East Coast and scale down to resolve the Fire Island nearshore. The model was validated using observations along western Fire Island and buoy data, and used to compute waves, currents and sediment fluxes. To isolate the influence of the SFCR on the generation of the persistent shoreline shape, simulations were performed with a linearized nearshore bathymetry to remove alongshore transport gradients associated with shoreline shape. The model accurately predicts the scale and variation of the alongshore transport that would generate the persistent shoreline undulations. In one location, however, the ridge crest connects to the nearshore and leads to an offshore‐directed transport that produces a difference in the shoreline shape. This qualitatively supports the hypothesized effect of cross‐shore fluxes on coastal evolution. Alongshore flows in the nearshore during a representative storm are driven by wave breaking, vortex force, advection and pressure gradient, all of which are affected by the SFCR.

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Section: Introductionmentioning

confidence: 99%

Persistent Shoreline Shape Induced From Offshore Geologic Framework: Effects of Shoreface Connected Ridges

et al. 2017

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“…The limited extent of nutrient-rich Mississippi River water to the Mississippi Bight coastal area suggests that other mechanisms such as submarine groundwater discharge (SGD) may play a role in the development of hypoxia. Indeed, SGD has been recognized as a significant source of nutrients to some coastal regions (e.g., Rodellas et al, 2015) and there are buried paleo-channels stretching from the Mississippi-Alabama coast (Flocks et al, 2015), which may serve as a conduit for SGD. Additionally, recent work by Peterson et al (2016) showed evidence of development of hypoxia off South Carolina due to the discharge of cold, salty, anoxic groundwater.…”

Section: Discussionmentioning

confidence: 99%

Extent of Mississippi River water in the Mississippi Bight and Louisiana Shelf based on water isotopes

Sanial

Shiller

Joung

et al. 2019

Estuarine, Coastal and Shelf Science

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The northern Gulf of Mexico is a complex and very productive coastal river-dominated system that receives freshwater from numerous rivers including the Mississippi River. The dynamics of coastal ecosystems in the northern Gulf of Mexico are greatly influenced by the freshwater discharge but also by the high nutrient loads carried by the Mississippi River that lead to the seasonal development of one of the largest coastal hypoxic areas. Constraining the origin and fate of the freshwater inputs in the northern Gulf of Mexico will help increase understanding the physical and biogeochemical processes occurring in this region. Here, we focus on investigating the extent of the Mississippi River plume on both sides of the Mississippi River Delta: to the east in the Mississippi Bight, and to the west over the Louisiana Shelf. We determined the water isotopic signature (δ 18 O and δD) along with salinity of the different river plumes and performed a river mixing model on the coastal waters. Our findings provide useful information to better understand the functioning of the northern Gulf of Mexico ecosystem. In particular, the development of hypoxia is often attributed to the nutrient load of the Mississippi River, yet the Mississippi River seemed to have a limited influence on the Mississippi Bight. That is, the dominant source of freshwater in the Bight was supplied by local Mississippi/Alabama rivers. Furthermore, the water isotope mixing model showed that the source of freshwater to the Louisiana Shelf was dominated by the Atchafalaya River in summer, and by the Mississippi River during non-summer seasons. This pattern is consistent with the general shelf circulation that reverses in summer, but could not have been shown solely by the use of salinity.

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Coastal Barrier Preservation and Destruction

Otvos¹

2017

Encyclopedia of Earth Sciences Series

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Geologic control on the evolution of the inner shelf morphology offshore of the Mississippi barrier islands, northern Gulf of Mexico, USA

Cited by 10 publications

References 43 publications

Persistent Shoreline Shape Induced From Offshore Geologic Framework: Effects of Shoreface Connected Ridges

Persistent Shoreline Shape Induced From Offshore Geologic Framework: Effects of Shoreface Connected Ridges

Extent of Mississippi River water in the Mississippi Bight and Louisiana Shelf based on water isotopes

Coastal Barrier Preservation and Destruction

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