Export 4 results:
Sort by: Author Title Type [ Year  (Desc)]
Sinnett, G, Feddersen F.  2018.  The Competing Effects of Breaking Waves on Surfzone Heat Fluxes: Albedo Versus Wave Heating. Journal of Geophysical Research: Oceans. 123:7172-7184.   10.1029/2018JC014284   AbstractWebsite

Abstract Depth-limited wave breaking modifies the heat flux in the surfzone relative to the inner-shelf (where waves are not breaking). Surfzone wave breaking generates heat through viscous dissipation (wave heating), but also increases surface foam coverage and albedo, thereby reducing solar heating, that is, cooling relative to the inner-shelf. These two competing breaking wave effects are quantified with a yearlong experiment at the Scripps Institution of Oceanography Pier. Cross-shore averaged surfzone albedo estimates were more than three times higher than inner-shelf albedo, reducing the yearly averaged surfzone water-entering shortwave radiation by 41 W/m2 relative to the inner-shelf. Surfzone breaking wave dissipation added an additional yearly averaged 28 W/m2 relative to the inner-shelf. The albedo-induced solar heating reduction in spring, summer, and fall was usually greater than the wave heating. However, in winter, large waves and relatively weak shortwave solar radiation (due to both lower top of the atmosphere solar radiation and clouds) resulted in a nearly equal number of days of breaking wave-induced heating or cooling. These two heat flux terms are coupled via wave breaking dissipation. Averaged over the surfzone, the albedo-induced solar radiation reduction is linearly related to the downwelling solar radiation and is independent of wave height. Consequently, the albedo-induced cooling to wave heating ratio is a function of breaking wave height to the −3/2 power, allowing evaluation of the relative importance of these terms in other geographic regions.

Sinnett, G, Feddersen F, Lucas AJ, Pawlak G, Terrill E.  2018.  Observations of Nonlinear Internal Wave Run-Up to the Surfzone. Journal of Physical Oceanography. 48:531-554.   10.1175/JPO-D-17-0210.1   AbstractWebsite

AbstractThe cross-shore evolution of nonlinear internal waves (NLIWs) from 8-m depth to shore was observed by a dense thermistor array and ADCP. Isotherm oscillations spanned much of the water column at a variety of periods. At times, NLIWs propagated into the surfzone, decreasing temperature by ≈1°C in 5 min. When stratification was strong, temperature variability was strong and coherent from 18- to 6-m depth at semidiurnal and harmonic periods. When stratification weakened, temperature variability decreased and was incoherent between 18- and 6-m depth at all frequencies. At 8-m depth, onshore coherently propagating NLIW events had associated rapid temperature drops (ΔT) up to 1.7°C, front velocity between 1.4 and 7.4 cm s−1, and incidence angles between −5° and 23°. Front position, ΔT, and two-layer equivalent height zIW of four events were tracked upslope until propagation terminated. Front position was quadratic in time, and normalized ΔT and zIW both decreased, collapsing as a linearly decaying function of normalized cross-shore distance. Front speed and deceleration are consistent with two-layer upslope gravity current scalings. During NLIW rundown, near-surface cooling and near-bottom warming at 8-m depth coincide with a critical gradient Richardson number, indicating shear-driven mixing.

Sinnett, G, Feddersen F.  2016.  Observations and parameterizations of surfzone albedo. Methods in Oceanography. 17:319-334.   10.1016/j.mio.2016.07.001  
Sinnett, G, Feddersen F.  2014.  The surf zone heat budget: The effect of wave heating. Geophysical Research Letters. 41   10.1002/2014GL061398