Authors: Angélica Romero-Arteaga, Amaia Ruiz de Alegría-Arzaburu, David Rivas, Braulio Juarez
https://doi.org/10.1016/j.csr.2022.104697
Abstract
Yearly-average along-shelf winds were predominantly upcoast over the last two decades, but large seasonal fluctuations existed. This study provides an example of how the passage of episodic cold fronts generally induce the reversing of along-shelf flows downcoast on the southern Texas coast. A total of 819 cold fronts of 4 days of average duration were identified between 1984 and 2018, and the vertical structure of the flow was analyzed for 38 cold fronts between November 2016 and October 2018 at a location 10 km offshore of Port Aransas. Cold fronts were identified based on local wind speeds and directions and synoptic-scale mean sea-level pressure differences, and then categorized through hierarchical clustering. Theoretical flow expectation for unstratified conditions suggested that the flow response was primarily controlled by the wind forcing during the passage of cold fronts. Detailed analysis on the vertical profile of the flow demonstrated significant time-lag differences, mainly related to the front intensity and duration. Strongest downcoast flows of −0.5 ms−1 encompassing the entire water column (18 m depth) were associated with individual fronts of high intensity ( of ∼ −0.15 Nm−2) and long duration (at least 4 days). The most common fronts were individual of low intensity ( of ∼ −0.05 Nm−2) and short duration (up to 2 days), and induced relatively weak downcoast currents of up to −0.2 ms−1, and in many cases, these were unable to completely reverse the flow downcoast. This study highlights the relevant role of episodic cold fronts in reversing and intensifying inner-shelf currents on the southern Texas coast, and emphasizes differences in the flow response related to cold front characteristics.
Keywords: Hydrodynamics, ADCP data, Wind-induced currents, Nortes, Synoptic-scale wind
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