Date of Award

Fall 2019

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

School

Ocean Science and Engineering

Committee Chair

Stephan D. Howden

Committee Chair School

Ocean Science and Engineering

Committee Member 2

Dmitri A. Nechaev

Committee Member 2 School

Ocean Science and Engineering

Committee Member 3

Jeremy D. Wiggert

Committee Member 3 School

Ocean Science and Engineering

Committee Member 4

Patrick J. Fitzpatrick

Committee Member 5

Davin J. Wallace

Committee Member 5 School

Ocean Science and Engineering

Abstract

The Mississippi-Alabama barrier islands restrict exchange between the Mississippi Sound and Mississippi Bight in the northern Gulf of Mexico. The islands also act as storm breaks for tropical cyclones, so their continued existence sustains marine ecosystems and protects coastal communities. However, the chain has undergone extensive segmentation, erosion, and westward migration in the past two hundred years. The islands are now more susceptible to further erosion (Pendleton et al., 2013; Morton, 2007). Additional reduction in island subaerial land extent would alter circulation in the Mississippi Sound and Bight.

Consequently, this study targeted the two most vulnerable barrier islands in the chain for removal in an ocean model to understand how circulation might change in an island loss scenario. A multiplatform data analysis assessed patterns in existing circulation over a four year period. Circulation varied both seasonally and on short time scales ranging from hours to days. Additionally, storm-induced changes to circulation were examined for the hurricane seasons of the same four year period to gauge how non-periodic events impacted the Mississippi Sound and Bight. Circulation response to tropical cyclones that entered the Gulf of Mexico varied storm to storm. Prior to initiating the island removal scenarios, validation of the oceanic and atmospheric models was completed to deduce model skill using the observational data.

Finally, the response of Mississippi Sound and Bight circulation to island loss was examined under time-invariant and time-variant conditions. Analysis of model output found island removal weakened currents in existing island passes but created new water exchange pathways where the islands had been removed. The new pathways increased salinity within the Mississippi Sound by as much as 2 near the removed islands. However, the island chosen for removal dictated the extent of circulation changes and which half of the Sound saw larger salinity increases. Seasonality played a role in how the Mississippi Sound and Bight responded to island loss. Results suggest permanent changes to circulation which would impact the resiliency of the remaining barrier islands and substantially shift distributions of hydrographic properties. These changes would have ecological and economic consequences throughout the Mississippi Sound.

ORCID ID

0000-0001-8274-4035

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