Date of Award

Summer 2021

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Ocean and Earth Sciences

Committee Director

Tal Ezer

Committee Member

Sophie Clayton

Committee Member

Sönke Dangendorf

Abstract

Surface currents in the lower Chesapeake Bay (CB) observed with land-based high-frequency radar antennas, or Coastal Ocean Dynamics Application Radar (CODAR), produce hourly 2D maps of current velocities used for search and rescue, pollution tracking, and fishing operations. This study analyzes the correlations between a 9-year record of surface currents measured by CODAR to coastal sea level, local wind forcing, river discharge into CB, and water transport through the Florida Straits, representing the Gulf Stream’s control on sea level along the U.S. mid-Atlantic coast. The goal of this study is to find ways to use CODAR data to detect and monitor long-term sea level changes in CB, which may aide numerical modeling of the lower Bay for long-term forecasting and trend analysis.

Linear regression, spectral and wavelet analyses, and Empirical Mode Decomposition (EMD) are applied to the datasets. Linear regression and spectral analysis show high frequencies of CODAR surface currents driven primarily by winds and link to variations in water levels, while low frequencies explained by river discharge and Gulf Stream. Both spectral and wavelet capture the annual cycle, wavelet suggesting anti-correlation between CODAR outflow and water level at this period. Because these methods only capture signals up to about two years, EMD, which separates lower frequency oscillating modes, is also used. EMD trendlines are qualitatively consistent with known dynamics or may be part of larger decadal oscillations longer than this 9-year dataset. Spectral and EMD agree at high frequencies, but also suggests river and Gulf Stream flow may be linked with CODAR currents on longer time scales. EMD achieves realistic long-term trends and correlations for CODAR, but a longer time series is necessary to produce significant results that could use this data to truly monitor long-term sea level changes for the CB in this manner. The study demonstrated the complex nature and interconnections between the different factors and different time scales affecting the currents at the mouth of the CB. This analysis may be the first of its kind in the attempt at combining all these different observations in a single study.

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DOI

10.25777/4765-dh54

ISBN

9798460436125

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