Eddy Vertical Structure and Variability: vortex evolution and the geography of geostrophic turbulence

• Main Author: Steinberg, Jacob Michael
• Other Authors: Eriksen, Charles C
• Format: Thesis
• Language: English
• Published: 2020
• Subjects: eddy evolution and decay; eddy vertical structure; geostrophic turbulence; simulated glider sampling; submesoscale coherent vortices; Physical oceanography; Oceanography; North Atlantic
• Online Access: http://hdl.handle.net/1773/45538

Thesis (Ph.D.)--University of Washington, 2020 Glider observations of submesoscale and mesoscale eddy structure, behavior, and evolution are analyzed revealing both processes of eddy decay and statistical properties of geostrophic turbulence (i.e. mesoscale eddy-eddy interactions resulting in energy transfer across scales). These observations, made by Seaglider and Deepglider autonomous underwater vehicles, and their interpretation are split into three sections: 1) the observed evolution and decay of a single California Undercurrent eddy, 2) sampling platform biases and aliasing diagnosed via simulated glider sampling in high resolution ocean models, and 3) observations of geostrophic turbulence from eddy vertical structure in the North Atlantic (analysis of hundreds of full-depth profiles of isopycnal vertical displacement and geostrophic velocity). Three Seagliders, deployed off of the Washington coast in 2013, located a subsurface intensified California Undercurrent eddy completing repeat eddy-bisecting transects over a three month period. These transects were used to create and compare `snapshots' of eddy depth-radial structure at different times. The observed evolution of this eddy can be explained by both adjustment to new background conditions, weaker stratification at the eddy core depth and translation multiple degrees northward, and decay via lateral thermohaline intrusions. Eddy total mechanical energy, salt content, and the magnitude of the core potential vorticity anomaly all decreased while core spice and dissolved oxygen variance increased tenfold. While these coherent eddies are capable of translating hundreds of kilometers away from their formation sites, both adjustment and decay appear as relevant processes moderating their behavior. The idealized simulation of full-depth glider sampling in two high resolution ocean models was then carried out to quantify the accuracy of glider derived profiles of isopycnal vertical displacement and geostrophic velocity. These profiles are interpreted in the ...