Alongshore Momentum Budget Variations Over a Fringing Coral Reef

Isabella Beatriz Arzeno, University of California, San Diego, Scripps Institution of Oceanography, San Diego, CA, United States, Audric Collignon, University of California, San Diego, Mechanical and Aerospace Engineering, Sarah N Giddings, University of Washington, Seattle, WA, United States, Mark A Merrifield, Sch Ocean & Earth Sci & Tech, Honolulu, HI, United States and Geno R Pawlak, University of California San Diego, La Jolla, CA, United States
Abstract:
Fringing coral reefs play an important role in sediment transport, ecological dynamics, and energy fluxes. In particular, their high roughness results in strong vertical mixing of mass and momentum, and enhances wave dissipation. To further understand boundary layer processes associated with high reef roughness, an array of instruments was deployed during September 2013 between the 12m and 20m isobaths off the northwestern coast of Oahu, Hawai’i. The data includes spatial measurements of pressure, velocity, stratification and turbulence, with wind velocities obtained from an atmospheric model. Analysis of the tidal phase-averaged alongshore momentum budget shows that the pressure gradient is mostly balanced by inertial and bed stress forcing. Cross-shore variations of alongshore momentum are primarily caused by changes in the bottom friction coefficient due to differing roughness, wave, and current conditions. Additionally, we examine alongshore variations in the alongshore momentum budget along with modulations due to varying wave forcing and tidal conditions. Recognizing these changes in the momentum budget is critical to resolving effects of high reef roughness and improving coastal models.
Back to: Observations and Modeling of Physical Processes along Coral Reef-Lined Coasts I