A Two Decadal (1993–2012) Numerical Assessment of Sediment Dynamics in the Northern Gulf of Mexico

Zhengchen Zang,Qian Ge,Samuel J Bentley,Kehui Xu,Qin Chen,Eurico J D’Sa,Z George Xue

doi:10.3390/w11050938

Abstract

We adapted the coupled ocean-sediment transport model to the northern Gulf of Mexico to examine sediment dynamics on seasonal-to-decadal time scales as well as its response to decreased fluvial inputs from the Mississippi-Atchafalaya River. Sediment transport on the shelf exhibited contrasting conditions in a year, with strong westward transport in spring, fall, and winter, and relatively weak eastward transport in summer. Sedimentation rate varied from almost zero on the open shelf to more than 10 cm/year near river mouths. A phase shift in river discharge was detected in 1999 and was associated with the El Niño-Southern Oscillation (ENSO) event, after which, water and sediment fluxes decreased by ~20% and ~40%, respectively. Two sensitivity tests were carried out to examine the response of sediment dynamics to high and low river discharge, respectively. With a decreased fluvial supply, sediment flux and sedimentation rate were largely reduced in areas proximal to the deltas, which might accelerate the land loss in down-coast bays and estuaries. The results of two sensitivity tests indicated the decreased river discharge would largely affect sediment balance in waters around the delta. The impact from decreased fluvial input was minimum on the sandy shoals ~100 km west of the Mississippi Delta, where deposition of fluvial sediments was highly affected by winds.

Highlights

IntroductionThe Mississippi-Atchafalaya River system has the third largest drainage basin (3.3 × 106 km )
The Mississippi-Atchafalaya River system has the third largest drainage basin (3.3 × 106 km2 )and seventh largest freshwater discharge (380 km3 /year) in the world [1,2,3]
In this thissection section present the seasonal variations of hydrodynamics and dynamics, sediment followed by an analysis of sedimentation pattern over the

Summary

Introduction

The Mississippi-Atchafalaya River system has the third largest drainage basin (3.3 × 106 km ). Seventh largest freshwater discharge (380 km3 /year) in the world [1,2,3]. About two thirds of the sediments and water are delivered by the Mississippi River and the rest are diverted to the Atchafalaya River [4,5]. Especially after the 1950s, sediment flux from the Mississippi-Atchafalaya River has decreased dramatically [6,7,8,9]. The average rate of land loss was 88 km2 /year from 1956 to 2000, and an additional loss of 1329 km is projected by. Climate change within the Mississippi River watershed has been identified as a significant factor controlling long-term variations of river discharge.

Results

Discussion

Conclusion