Measuring Fluorescent Dye in the Bubbly and Sediment-Laden Surfzone

Clark, David B.; Feddersen, Falk; Omand, Melissa M.; Guza, R. T.

doi:10.1007/s11270-009-0030-z

Cited by 21 publications

(22 citation statements)

References 28 publications

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“…2.3.3. Cross-Shore Jetski Transects Surface dye concentration and temperature were measured with fluorometers and thermistors mounted on two GPS-tracked jetskis [Clark et al, 2009] that drove repeated cross-shore transects from x % 2300 m to the shoreline (e.g., Figure 1) at various designated alongshore locations between y 5 5 m and y % 2 km. The alongshore spacing between transects varied from approximately 20 m (near the release) to 300 m (far downstream of the release).…”

Section: Ib09 Experiments Methodsmentioning

confidence: 99%

“…All aerial and in situ dye observations are corrected for temperature per Smart and Laidlaw [1977], and all in situ dye observations are corrected for turbidity per Clark et al [2009]. Corrected D typically differs from measured D by less than 5%.…”

Section: Corrections To Measured Dye Fluorescencementioning

confidence: 99%

“…However, many of these observations were limited by sparse sampling or small spatiotemporal domains. A rapid-sampling, jetski-based dye measurement platform [Clark et al, 2009] provided improved observation methods. Analyses of dye plume evolution at Huntington Beach, California (HB06) showed that surfzone cross-shore tracer dispersion is dominated by horizontal eddies [Clark et al, 2010;Feddersen et al, 2011;Clark et al, 2011] forced by finite crest length wave breaking [Peregrine, 1998;Clark et al, 2012;Feddersen, 2014].…”

Section: Introductionmentioning

confidence: 99%

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Surfzone to inner‐shelf exchange estimated from dye tracer balances

et al. 2015

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Surfzone and inner‐shelf tracer dispersion are observed at an approximately alongshore‐uniform beach. Fluorescent Rhodamine WT dye, released near the shoreline continuously for 6.5 h, is advected alongshore by breaking‐wave‐ and wind‐driven currents, and ejected offshore from the surfzone to the inner‐shelf by transient rip currents. Novel aerial‐based multispectral dye concentration images and in situ measurements of dye, waves, and currents provide tracer transport and dilution observations spanning about 350 m cross‐shore and 3 km alongshore. Downstream dilution of near‐shoreline dye follows power law decay with exponent −0.33, implying that a tenfold increase in alongshore distance reduces the concentration about 50%. Coupled surfzone and inner‐shelf dye mass balances close, and in 5 h, roughly half of the surfzone‐released dye is transported offshore to the inner‐shelf. Observed cross‐shore transports are parameterized well ( , best fit slope ) using a bulk exchange velocity and mean surfzone to inner‐shelf dye concentration difference. The best fit cross‐shore exchange velocity is similar to a temperature‐derived exchange velocity on another day with similar wave conditions. The magnitude and observed inner‐shelf dye length scales, time scales, and vertical structure indicate the dominance of transient rip currents in surfzone to inner‐shelf cross‐shore exchange during moderate waves at this alongshore‐uniform beach.

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Section: Ib09 Experiments Methodsmentioning

confidence: 99%

Section: Corrections To Measured Dye Fluorescencementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Surfzone to inner‐shelf exchange estimated from dye tracer balances

et al. 2015

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“…In situ surface dye measurements were acquired with two jet ski-based dye sampling platforms that allow dye concentration measurements on cross-and alongshore transects in the near shore and through breaking waves in the surfzone (Clark et al 2009). Water pumped from 20 cm below the surface passes through a temperature sensor, a debubbler, a flow rate sensor, a Turner Designs Cyclops turbidity sensor, and a WetLabs WETStar Rhodamine WT fluorometer.…”

Section: Jet Ski-based In Situ Dye Samplermentioning

confidence: 99%

“…Dye tracer sources are known, and diffusivity estimates are improved relative to many natural tracers. Fluorescent dyes are accurately measured in situ with optical fluorometers, even in the surfzone with high concentrations of optical scatterers (Clark et al 2009). Nearshore dye sampling with hand-filled bottles (e.g., Harris et al 1963) has been improved upon with continuous in situ sampling techniques, which result in dye concentration transects or single-location time series (Fong and Stacey 2003;Clark et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Aerial Imaging of Fluorescent Dye in the Near Shore

Clark

Lenain

Feddersen

et al. 2014

Journal of Atmospheric and Oceanic Technology

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Aerial images are used to quantify the concentration of fluorescent Rhodamine water tracing (WT) dye in turbid and optically deep water. Tracer releases near the shoreline of an ocean beach and near a tidal inlet were observed with a two-band multispectral camera and a pushbroom hyperspectral imager, respectively. The aerial observations are compared with near-surface in situ measurements. The ratio of upwelling radiance near the Rhodamine WT excitation and emission peaks varies linearly with the in situ dye concentrations for concentrations ,20 ppb (r 2 5 0.70 and r 2 5 0.85-0.88 at the beach and inlet, respectively). The linear relationship allows for relative tracer concentration estimates without in situ calibration. The O(1 m) image pixels resolve complex flow structures on the inner shelf that transport and mix tracer.

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Cross‐shore tracer exchange between the surfzone and inner‐shelf

2014

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Cross-shore tracer exchange between the surfzone and inner-shelf is examined using temperature and dye measurements at an approximately alongshore-uniform beach. An alongshore-oriented plume is created by releasing dye continuously for 4.5 h in a surfzone alongshore current. The plume is sampled for 13 h from the release point to 700 m downstream, between the shoreline and 250 m offshore (6 m water depth). Within the surfzone ( 2 m depth), water is relatively warm, and dye is vertically well mixed. On the inner-shelf (3-6 m depth), alongshore currents are weak, and elevated temperature and dye co-occur in 25-50 m wide alongshore patches. Within the patches, dye is approximately depth-uniform in the warm upper 3 m where thermal stratification is weak, but decreases rapidly below 3 m with a strong thermocline. Dye and temperature vertical gradients are correlated, and dye is not observed below 18 C. The observations and a model indicate that, just seaward of the surfzone, thermal stratification inhibits vertical mixing to magnitudes similar to those in the ocean interior. Similar surfzone and inner-shelf mean alongshore dye dilution rates are consistent with inner-shelf dye properties being determined by local cross-shore advection. The alongshorepatchy and warm inner-shelf dye is ejected from the surfzone by transient rip currents. Estimated Stokes drift driven cross-shore exchange is small. The transient rip current driven depth-normalized heat flux out of the surfzone has magnitude similar to those of larger-scale shelf processes. Dye recycling, from the inner-shelf back to the surfzone, is suggested by relatively long surfzone dye residence times.

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Measuring Fluorescent Dye in the Bubbly and Sediment-Laden Surfzone

Cited by 21 publications

References 28 publications

Surfzone to inner‐shelf exchange estimated from dye tracer balances

Surfzone to inner‐shelf exchange estimated from dye tracer balances

Aerial Imaging of Fluorescent Dye in the Near Shore

Cross‐shore tracer exchange between the surfzone and inner‐shelf

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