IECOS - Instituto de Estudos Costeiros/Campus Bragança

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2228

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Agora exibindo 1 - 2 de 2

Acesso aberto (Open Access)
Nutrient and phytoplankton biomass in the Amazon River shelf waters
(2008-12) SANTOS, Maria de Lourdes Souza; MUNIZ, Kátia; BARROS NETO, Benício de; ARAUJO, Moacyr Cunha
The Amazon River estuary is notable at the Amazon Continental Shelf, where the presence of the large amount of water originating from the Amazon during the river's falling discharge period was made evident by the low salinity values and high nutrient levels. Even so, the presence of oceanic waters in the shelf area was significant. Dissolved organic nitrogen was the predominant species of the nitrogen cycle phases, followed by total particulate nitrogen, nitrate, ammonium and nitrite. The chlorophyll a data in the eutrophic area indicated that there is sufficient nitrogen in the area to withstand productivity, though dissolved inorganic nitrogen removal processes are faster than regeneration or mineralization. The anomalous amounts of inorganic dissolved nitrogen showed more removal than addition. The simulations with the bidimensional MAAC-2D model confirmed that high nutrient waters are displaced northwest-ward (two cores at 2.5ºN-50ºW and 4ºN-51ºW) by the stronger NBC during falling river discharge. During high river flow period these nutrient-rich lenses are distributed around 0.5ºN-48.5ºW as well as along the shallow Amazonian shelf (20m-50m depth, 1ºN-3.5ºN), as a result of the spreading of Amazon freshwater outflow.
Acesso aberto (Open Access)
Observações hidrológicas e resultados de modelagem no espalhamento sazonal e espacial da pluma de água Amazônica
(Instituto Nacional de Pesquisas da Amazônia, 2009) SILVA, Alex Costa da; SANTOS, Maria de Lourdes Souza; ARAUJO, Moacyr Cunha; BOURLÈS, Bernard
In this study, we present surface synoptic data collected during four oceanographic cruises undertaken in March-April 1995, October-November 1997, April-May 1999 and August-September 2001 in the Brazilian Program “REVIZEE/SCORE-NO” and a combination of model results (1/6 deg.). The emphasis of this paper is to point out the monthly changes on the spreading of the Amazon plume over the external Amazon shelf area and the eastern region of the Amazon River. Hydrographic data and model results demonstrated that during March-May, the Amazon plume moved southwestward along the northern coast of Brazil, decreasing during August-September; but this was not observed during October-November. Model results revealed ring signatures shedding from the North Brazil Current (NBC). Results also showed that during August the Amazon plume encircling the NBC retroflection was around 7º N.

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