Surface gravity wave transformation across a platform coral reef in the <scp>R</scp>ed <scp>S</scp>ea

Lentz, Steven J.; Churchill, James H.; Davis, Kristen A.; Farrar, J. Thomas

doi:10.1002/2015jc011142

Cited by 48 publications

(56 citation statements)

References 60 publications

(144 reference statements)

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“…Measurements of the wave friction factor f w from three sites on Palmya range from 0.4 to 5.7 (Figures and a), similar to field results from Lentz et al []. These results are higher than previous field studies on reefs from Nelson [] (N96), and Lowe et al .…”

Section: Wave Modelingmentioning

confidence: 89%

“…Recent work by Monismith et al . [] indicates wave friction on the structurally complex forereef at Palmyra (

f_{w} \approx

1.8) is significantly higher than previously measured on reefs at Kaneohe Bay, Hawaii (

f_{w} \approx

0.3) [ Lowe et al ., ], and John Brewer Reef, Australia (

f_{w} \approx

0.1) [ Nelson , ], but similar to results on a reef platform in the Red Sea ( f w = 0.2−5.0) [ Lentz et al , ].…”

Section: Introductionmentioning

confidence: 99%

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Wave dynamics of a Pacific Atoll with high frictional effects

et al. 2016

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We report field measurements of waves and currents made from September 2011 to July 2014 on Palmyra Atoll in the central Pacific that were used in conjunction with the SWAN wave model to characterize the wave dynamics operant on the atoll. Our results indicate that wave energy is primarily from the north during the northern hemisphere winter and from the south in the northern hemisphere summer. Refraction of waves along the reef terraces due to variations in bathymetry leads to focusing of waves in specific locations. Bottom friction, modeled with a modified bottom roughness formulation, is the significant source of wave energy dissipation on the atoll, a result that is consistent with available observations of wave damping on Palmyra. Indeed modeled wave dissipation rates from bottom friction are on average larger than dissipation rates due to breaking and are an order of magnitude larger than what has been observed on other, less geometrically complex reefs, a result which should be corroborated with future in situ measurements. The SWAN wave model with a modified bottom friction formulation better predicts bulk wave energy properties than the existing formulation at our measurement stations. The near bed squared velocity, a proxy for bottom stress, shows strong spatial variability across the atoll and exerts control over geomorphic structure and benthic community composition.

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Section: Wave Modelingmentioning

confidence: 89%

“…Recent work by Monismith et al . [] indicates wave friction on the structurally complex forereef at Palmyra (

f_{w} \approx

1.8) is significantly higher than previously measured on reefs at Kaneohe Bay, Hawaii (

f_{w} \approx

0.3) [ Lowe et al ., ], and John Brewer Reef, Australia (

f_{w} \approx

0.1) [ Nelson , ], but similar to results on a reef platform in the Red Sea ( f w = 0.2−5.0) [ Lentz et al , ].…”

Section: Introductionmentioning

confidence: 99%

Wave dynamics of a Pacific Atoll with high frictional effects

et al. 2016

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“…To estimate significant wave height and peak wave period, the Seagauges at all sites except RN, sampled at 2 Hz for 512 s bursts every 4 h (for details on surface wave measurements and processing, see Lentz et al . []). Seagauges were outfitted with parallel plate ports to reduce pressure perturbations associated with the flow impinging on the pressure port (Bernoulli effects).…”

Section: Field Program and Processingmentioning

confidence: 99%

“…This set‐down is small and since it is a local Bernoulli balance between the wave kinetic energy and the sea level it has no impact on the reef current dynamics.) Wave reflection would slightly alter the wave‐momentum flux onto the reef, but there is no discernible evidence of wave reflection in the directional spectrum from the ADCP just offshore of the reef [ Lentz et al ., ]. Assuming water depth is independent of x over the reef flat,

D (x, t) \sim D (t)

, and the wave‐radiation stress is small at the back of the reef relative to the front,

S_{x x} (x_{f}) - S_{x x} (x_{b}) \approx S_{x x} (x_{f})

, (7) reduces to

U false| U false| \approx \frac{true(- S_{x x}^{i} / Δ x + τ^{s x} true)}{ρ C_{d a}} \to U \approx s g n (- S_{x x}^{i} / Δ x + τ^{s x}) \sqrt{\frac{false| - S_{x x}^{i} / Δ x + τ^{s x} false|}{ρ C_{d a}}},

where

S_{x x}^{i}

is the incident wave‐radiation stress and Δ x = x b − x f .…”

Section: Model Frameworkmentioning

confidence: 99%

The characteristics and dynamics of wave‐driven flow across a platform coral reef in the Red Sea

et al. 2016

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Current dynamics across a platform reef in the Red Sea near Jeddah, Saudi Arabia, are examined using 18 months of current profile, pressure, surface wave, and wind observations. The platform reef is 700 m long, 200 m across with spatial and temporal variations in water depth over the reef ranging from 0.6 to 1.6 m. Surface waves breaking at the seaward edge of the reef cause a 2–10 cm setup of sea level that drives cross‐reef currents of 5–20 cm s−1. Bottom stress is a significant component of the wave setup balance in the surf zone. Over the reef flat, where waves are not breaking, the cross‐reef pressure gradient associated with wave setup is balanced by bottom stress. The quadratic drag coefficient for the depth‐average flow decreases with increasing water depth from Cda = 0.17 in 0.4 m of water to Cda = 0.03 in 1.2 m of water. The observed dependence of the drag coefficient on water depth is consistent with open‐channel flow theory and a hydrodynamic roughness of zo = 0.06 m. A simple one‐dimensional model driven by incident surface waves and wind stress accurately reproduces the observed depth‐averaged cross‐reef currents and a portion of the weaker along‐reef currents over the focus reef and two other Red Sea platform reefs. The model indicates the cross‐reef current is wave forced and the along‐reef current is partially wind forced.

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“…Depth‐induced wave breaking can also result in generation of free infragravity (IG) waves (0.004–0.04 Hz), which have been found to account for a larger proportion of total IG wave energy than bound IG waves at reefs where wave breaking occurs (Baldock, ; Bertin et al, ; Ferrario et al, ; Pomeroy et al, , ; van Dongeren et al, ). Although wave breaking and resultant wave‐driven circulation are dominant processes in many reef systems, the relatively high hydrodynamic roughness of coral reefs compared to sandy environments can result in a substantial fraction of wave energy dissipation due to bottom friction under lower‐energy conditions (Lentz et al, ; Lowe et al, ).…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamics and Sediment Mobility Processes Over a Degraded Senile Coral Reef

et al. 2018

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Coral reefs can influence hydrodynamics and morphodynamics by dissipating and refracting incident wave energy, modifying circulation patterns, and altering sediment transport pathways. In this study, the sediment and hydrodynamic response of a senile (dead) barrier reef (Crocker Reef, located in the upper portion of the Florida Reef Tract) to storms and quiescent conditions was evaluated using field observations and the Coupled Ocean-Atmosphere-Wave-Sediment Transport model. Waves, circulation, and resultant sediment mobility were modeled across different reef zones. Sediment mobility during quiescent periods and the passage of far-field storms are driven by nonbreaking waves and, to a lesser degree, regional circulation. Spatial variability in these processes produces the present-day distribution of sediment grain size at Crocker Reef, wherein finer-grain material along a shallow central ridge is frequently mobilized (43% to 62% of the time), winnowed away, and deposited along the lower-energy flanks and in the fore reef where sand mobility occurs less frequently (32% to 43% and 1% to 22% of the time, respectively). Analysis of wave conditions for the period of 2006-2014 supports that wave heights rarely exceed the threshold for breaking (0.1% and 0.3% at the reef crest and at the reef flat, respectively), predominantly during the passage of tropical storms. There is a shift to a wave-breaking regime during near-field storms, creating the potential for mobilization of larger material and enhanced reef degradation. Sediment mobility can be enhanced due to wave skewness or the generation of free infragravity waves during periods of depth-induced wave breaking.

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Surface gravity wave transformation across a platform coral reef in the Red Sea

Cited by 48 publications

References 60 publications

Wave dynamics of a Pacific Atoll with high frictional effects

Wave dynamics of a Pacific Atoll with high frictional effects

The characteristics and dynamics of wave‐driven flow across a platform coral reef in the Red Sea

Hydrodynamics and Sediment Mobility Processes Over a Degraded Senile Coral Reef

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