Processos oceanográficos na região costeira e estuarina do Rio Caeté, Pará, Brasil

• Ano de defesa: 2007
• Autor(a) principal: Cavalcante Segundo, Geórgenes Hilário
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Programa de Pós-graduação em Geoquímica Ambiental; Geoquímica
• Palavras-chave em Português: Circulação, Marés, Ventos, Descarga Fluvial, Transporte de Sal.; Circulation, Tides, Winds, River Discharge, Salt Transport.; CNPQ::CIENCIAS EXATAS E DA TERRA::GEOCIENCIAS::GEOLOGIA::GEOQUIMICA
• Link de acesso: https://app.uff.br/riuff/handle/1/17372

The aim of the present study is to understand the main physical processes in the coastal area of Pará and estuarine coastal system of the Caeté River. The methodology bases on a data set of current velocity, hydrographic data, tidal stations, meteorological stations, data from satellite sensors, and previous studies of the regional geomorphology, assessing the correlation and variability of theses parameters for several years. By evaluating the variability of the Intertropical Convergence Zone (ITCZ), it was verified that the winds blow mostly from the north-northeast during the austral summer, whereas during the austral winter, a band of easterly-northeasterly winds prevail, associated with displacement of the ITCZ towards to North Hemisphere. Perpendicular winds forcing upon the Pará coast are more significant than the parallel winds. The wind energy showed a frequency of 58.5 % (northeast) following for east/north directions 20.7 % / 11.5 %, respectively. At the northern premises of the Pará coast, a surface water mass with a salinity of 12, denominated locally as black water , flowed towards the SE at a speed of 0.78 m s-1, which likely originated from the Amazonian Pará River. These new results reveal a possible influence of these waters upon coastal circulation, generating a stratification current. The current structure and salinity patterns off the caet~e estuary mouth, were controlled by river discharge, tidal forcing, wind persistence and possible also small-scale coastal eddies. The re-circulation system found about 32 km further offshore, seemed to have been driven by a local eddy. The seaward limit of the Caeté river frontal zone lies at around the 30 m isobath, being variable in accordance to the tidal period and/or river discharge. The measurements undertaken in the Caeté River estuary, revealed a dynamic environment and partially mixed conditions, alternating from highly stratified to weakly stratified. The net salt transport was driven by river discharge followed by the Stokes drift and tidal diffusion. The Bragança coastal region has been subject to severe erosion, with a retreat of 32 km2 and accretion of 20 km2, resulting in a mangrove land loss of almost 12 km2 over the last three decades. In all, a reasonable amount of knowledge on the coastal-shelf dynamics of the Amazon and Pará coast is now available. Motions on the Amazon Shelf are forced mainly by tides, wind stress and the North Brazil Current. Nevertheless, more studies are needed on the physical mechanisms which control transport at the inner coastal-shelf area of Pará, the seasonal cycle of stratification, and the impact by river discharges. From a practical point of view, the present results may be applied to the development of management programs, which are necessary due to the increase of anthropogenic impacts during the last years.