Observations and modeling of a tidal inlet dye tracer plume

TitleObservations and modeling of a tidal inlet dye tracer plume
Publication TypeJournal Article
Year of Publication2016
AuthorsFeddersen F, Olabarrieta M., Guza RT, Winters D., Raubenheimer B., Elgar S.
JournalJournal of Geophysical Research-Oceans
Volume121
Pagination7819-7844
Date Published2016/10
Type of ArticleArticle
ISBN Number2169-9275
Accession NumberWOS:000388602200034
Keywordsboundary-layer; buoyant; circulation; coastal waters; currents; ebb-tidal plume; longshore; momentum balances; river plume; surf zone; system; tidal inlet; tracer transport; wave-current interaction
Abstract

A 9 km long tracer plume was created by continuously releasing Rhodamine WT dye for 2.2 h during ebb tide within the southern edge of the main tidal channel at New River Inlet, NC on 7 May 2012, with highly obliquely incident waves and alongshore winds. Over 6 h from release, COAWST (coupled ROMS and SWAN, including wave, wind, and tidal forcing) modeled dye compares well with (aerial hyperspectral and in situ) observed dye concentration. Dye first was transported rapidly seaward along the main channel and partially advected across the ebb-tidal shoal until reaching the offshore edge of the shoal. Dye did not eject offshore in an ebb-tidal jet because the obliquely incident breaking waves retarded the inlet-mouth ebb-tidal flow and forced currents along the ebb shoal. The dye plume largely was confined to <4 m depth. Dye was then transported downcoast in the narrow (few 100 m wide) surfzone of the beach bordering the inlet at 0.3 ms-1 driven by wave breaking. Over 6 h, the dye plume is not significantly affected by buoyancy. Observed dye mass balances close indicating all released dye is accounted for. Modeled and observed dye behaviors are qualitatively similar. The model simulates well the evolution of the dye center of mass, lateral spreading, surface area, and maximum concentration, as well as regional (inlet and ocean) dye mass balances. This indicates that the model represents well the dynamics of the ebb-tidal dye plume. Details of the dye transport pathways across the ebb shoal are modeled poorly perhaps owing to low-resolution and smoothed model bathymetry. Wave forcing effects have a large impact on the dye transport.

DOI10.1002/2016jc011922
Short TitleJ Geophys Res-Oceans
Student Publication: 
No