Wave Power Long-term Mean, 2002-2012 - American Samoa

Wave power is a major environmental forcing mechanism that influences a number of marine ecosystem processes including coral reef community development, structure, and persistence. By driving mixing of the upper water column, wave forcing can also play a role in nutrient availability and ocean temperature reduction during warming events. Wave forcing can be highly seasonal, with winter months typically experiencing far greater wave power than that experienced during the summer months. This layer represents the mean of maximum daily wave power (kW/m) from 2002-2012. In the absence of numerical wave model and wave forcing observational site-level data at the desired spatial resolution, a wave exposure proxy, developed by S. Jeanette Clark, is used to examine wave exposure. Wave energy estimates were derived at 1-km resolution utilizing NOAA WaveWatch III (WW3) global 0.5-deg wave model data and coastline analysis of wave exposure. This is achieved by: 1) Determining the incident wave swath for a specific site at an island using a 360-degree radial plot and degree-bin elimination based on a swath's intersection with land or relevant bathymetric contour. 2) Selecting the closest WW3 pixel and extracting the time series for significant wave height, peak period, and peak direction. 3) Calculating wave power (kW/m) with significant wave height and peak period using the following equation: Ef = pg / 64pi * Hs^2 * Tp / 1000 where p is the density of sea water (1024 kg m-3), g is the acceleration of gravity (9.8 m s-2), Hs is the offshore significant wave height, and Tp is the dominant wave period (1/wavelength). 4) Lastly, annual wave power data are filtered and organized into respective degree bins based on peak direction and summed to give a wave power estimate at each site. The wave power metric calculated here is based on offshore wave height and does not account for variation with depth.