Variability of Wave Spectra Conditions in the Amazon Barrier Coast

Abstract

Guerreiro, J.; Souza, E., and El-Robrini, M., 2020. Variability of wave spectra conditions in the Amazon Barrier Coast. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1411–1415. Coconut Creek (Florida), ISSN 0749-0208.A characterization of Amazon Barrier Coast (Tropical Atlantic) wave conditions is presented, seeking to understand interannual variations in the wave spectrum based on wave data measured on a high-energy macrotidal beach and on modelled data from Era-I (ECMWF). The temporal variation of the wave spectrum indicates similar variation in both measured and modelled data, being considerable from winter to summer. High wind speeds during the Amazonian summer generate the predominance of windsea waves from June to September with higher Power spectral density (PSD) at 0.17 Hz and variations in the direction from NNE, NE and SE. While moderate wind speeds along the southern position of precipitation belt, Intertropical Convergence Zone (ITCZ), lead to swell (0.07 Hz) and windsea (0.13 Hz) waves occurring in the tropical autumn (October to December), and directions preferably from NNE; and in the winter from January to April variations from NNE, NE and SE. However, the temporal variation in PSD in both measured and modelled data differs due to the protective effect of wave action by submerged sandy banks that attenuate the amount of energy reaching the coastline, therefore, incoming energy is attenuated by almost 60% of offshore wave energy. Thus, the spectral wave conditions in the tropical Atlantic are influenced by the northern and southern migration of the precipitation belt, as the seasons changes to the dry (summer) and rainy (winter) seasons and also by the bottom morphology near the shoreline.