Date of Award
5-2026
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
School
Ocean Science and Engineering
Committee Chair
Stephan Howden
Committee Chair School
Ocean Science and Engineering
Committee Member 2
Christopher Hayes
Committee Member 2 School
Ocean Science and Engineering
Committee Member 3
Arne Diercks
Committee Member 3 School
Ocean Science and Engineering
Committee Member 4
Diana Bernstein
Committee Member 4 School
Ocean Science and Engineering
Committee Member 5
Kristina Mojica
Committee Member 5 School
Ocean Science and Engineering
Committee Member 6
Jun A. Zhang
Abstract
In this dissertation, I examine and discuss different ocean features and ocean processes essential to the intensification of tropical cyclones in the Gulf of Mexico, drawing on observations, theory, and numerical model analyses across both the deep ocean and continental shelf-regimes. In the deep ocean, I integrate in situ measurements, theoretical framework, a 1D shear driven mixed layer model, and a high resolution model outputs to evaluate how salinity-driven stratification, Loop Current warm core eddies, pre-existing warm mixed layer temperatures, and the governing mechanisms mixed layer adjustment shape the upper ocean response before, during, and after storm passage. In the coastal region, while the focus is on the physical and environmental factors responsible that sustained Hurricane Ida’s intensification, I also examined the associated shelf circulation and biogeochemical response during Hurricane Ida’s transit across the Louisiana shelf. Chapter Two uses a coordinated hurricane glider observations and coupled atmosphere-ocean model to quantify how salinity-driven stratification and warm core eddies modulated the upper ocean response during Hurricane Sally (2020). I show that freshwater from river discharge established a low salinity barrier layer that decoupled the mixed layer from the ocean interior, reducing the mixed layer cooling by 38%. This analysis underscores the need for operational hurricane forecasts models to incorporate real-time freshwater (river) discharge and to represent the spatial and temporal evolution of river plumes in the Gulf of Mexico. Chapter Three demonstrates that, in the absence of the anomalously warm pre-storm mixed layer temperature of 30oC, surface temperatures could have cooled down to 28.5oC, supporting the hypothesis that thermal structures of the Loop Current warm core eddies rarely undergo substantial cooling during hurricane passage. Using a mixed layer heat budget, I quantify vertical mixing, surface heat fluxes, and advection within a unified observational framework, and I emphasize the extreme and rare upper ocean conditions during Hurricane Laura. Chapter Four shows that Hurricane Ida’s cross-shelf transit generated cross-shelf currents, with shoreward advection in the surface boundary layer and enhanced transport within the bottom boundary layer. Focusing on days surrounding August 29 2021, I document a marked biogeochemical response: seawater pCO2 increased from 298.5μatm to 372.7μatm, following Hurricane Ida’s passage, reflecting the combined influence of vertical mixing, coastal circulation, and storm-driven redistribution of carbon-rich waters.
Copyright
Senam Tsei, 2026
Recommended Citation
TSEI, Senam Kofi, "An Assessment of the Deep and Coastal Responses to Hurricane Passage in the Gulf of Mexico, Using Complementary Observational Records and Model Simulations" (2026). Dissertations. 2472.
https://aquila.usm.edu/dissertations/2472