Date of Completion

3-29-2019

Embargo Period

3-29-2019

Keywords

Western Long Island Sound, Fetch-limited Coastal Basin, Waves, Wind, Asymmetry

Major Advisor

James O'Donnell

Associate Advisor

W. Frank Bohlen

Associate Advisor

Michael M. Whitney

Associate Advisor

Anthony Kirincich

Associate Advisor

David Ullman

Field of Study

Oceanography

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

A study of 8 years of observations from a buoy in western Long Island Sound shows that the wave field has an asymmetric response to wind direction. Waves are bigger when the wind blows from the east. Comparison to empirical models shows that the behavior is consistent with fetch limited wave growth when bottom dissipation is included.

Using 3 years of current observations at, and near, the surface, I show that the near surface shear also has an asymmetric response to wind. The shear is greater when the wind blows from the west. I then compare estimates of the near surface eddy viscosity for a range of wind stress values, of both signs, and show that the eddy viscosity is up to a factor of 5 greater when the wind is from the east.

A comparison of the variation of eddy viscosity coefficients with Henderson’s theory (Henderson et al., 2013), that describes the effect of waves on the eddy viscosity, shows that the observed response to wind directions is consistent with the predicted behavior. To assess the potential impact of surface intensification of the eddy viscosity on the wind driven flow in the estuary, I expand the model of Winant (2004) to include vertically variations in the eddy coefficient structure and use the finite element method to obtain solutions in the center of the domain. For geometries similar to that of Long Island Sound, I show that the vertical current structures are much different from those which assume constant eddy viscosity coefficients and present evidence from current measurements that the variable eddy coefficient model provides a better representation of the flow.

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