Wave climate and power distribution around a rocky island: Alcatrazes, Brazil

Abstract

We investigate the distribution of the wave power around the Alcatrazes island, a protected marine reserve in southeastern Brazil, located at 20 nautical miles from the coast of São Sebastião/SP. A 14-year wave time series (2005-2018) extracted from the global WaveWatch III model, was used to obtain the offshore wave climate. Based on the wave climate, a wave propagation model (Delft3D) was applied in order to obtain nearshore information. The most frequent waves are from the east, southeast and south, with heights between 1.0 and 2.0 m and periods of 7 to 10 s. Due to dominant wave direction incidence, the wave power is higher at the more exposed eastern side of the island, with its lee side becoming shadowed from the main wave trains. Magnitudes vary seasonally, with winter and autumn presenting more energetic southerly waves and consequent higher wave power along the rocky island. The wave power distribution is a consequence of the incident wave characteristics and the geomorphology of the island. Our findings are the first assessment of the local wave climate and wave power distribution along the rocky shores of Alcatrazes island, providing important background information for understanding different aspects of its functioning and management.