Observações hidrológicas e resultados de modelagem no espalhamento sazonal e espacial da pluma de água Amazônica

Abstract

ResumoNeste estudo são apresentadas as análises espaciais e temporais dos dados sinóticos coletados durante quatro campanhas oceanográficas do programa "REVIZEE/SCORE-N" realizadas em março-abril de 1995, outubro-novembro de 1997, abrilmaio de 1999 e agosto-setembro de 2001. Em complemento às análises dos dados hidrológicos, foram utilizados resultados do modelo numérico CLIPPER -Experimento ATL6 (1/6 deg.). A ênfase deste artigo é avaliar o deslocamento sazonal e espacial da pluma de água Amazônica nas regiões localizadas à sudoeste, noroeste e em frente à foz do rio Amazonas. Dados hidrológicos e resultados do modelo demonstram que durante os meses de março-maio a pluma do rio Amazonas move-se para sudoeste, ao longo da costa norte brasileiro, tendendo a diminuir o deslocamento da pluma para sudoeste durante os meses de agosto-setembro. De outubro a novembro, não foi observado ou registrado o deslocamento da pluma para sudoeste. Resultados do modelo revelam anéis gerados pela retroflexão da Corrente Norte do Brasil (CNB) em torno de 7º N, e também a influência de água proveniente do rio Amazonas em volta desses anéis durante o mês de agosto.PalavRas-chave: Pluma do rio Amazonas; anéis; Corrente Norte do Brasil; modelo Atlântico; dados do REVIZEE. Hydrological observations and modeling results of the seasonal and spatial spread of the Amazonian water plume abstRactIn 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.

Larval dispersal of Brachyura in the largest estuarine / marine system in the world

“…In the export process, Brachyura larvae are carried along the plume edge towards the ACS. In the maximum flow conditions, the Amazon plume can extend up to 300 km from the coast [76] and up to 10 meters deep [77], with salinity below 35 [78]. The plume edge is usually controlled by both, wind and Ekman flow, so that the balance of the wind mix (which undoes the vertical stratification) and the Ekman transport by buoyancy (which reinforces the vertical stratification) results in a plume edge with slowly increasing salinity as it moves into the sea carrying the larvae [79][80][81].…”

“…Given this, knowing the larval distribution of families in the different strata of the water column is relevant for future sampling, where oblique hauling has proven to be effective in capturing Ocypodidae larvae, Armases and Calappa, while surface hauling is ideal for sampling Panopeidae, Pinnotheridae and Portunidae in the ACS. The Amazon fluvial discharge affects the dispersion of estuarine families while the Amazon plume influences the species of the continental shelf, being responsible for the continuous distribution of nutrients on the ACS [76] and increasing the primary ocean production in the area. Moreover, the area connecting the ACS and the coast consists of mangroves of the Amazon River mouth, considered a Ramsar site, is extremely important for numerous aquatic organisms, whether as habitat, feeding zone, or nursery [174,175].…”

Factors affecting the seasonal variability of planktonic shrimps (Dendrobranchiata) along an estuary–ocean gradient on the Amazon continental shelf

“…The Amazon River outflow varies seasonally, ranging from ∼220,000 m 3 s −1 in May (maximum flooding of the river) to 100, 000 m 3 s −1 in November (low flow period) (Geyer et al, 1996;Silva et al, 2009;Molleri et al, 2010), and it forms a lowsalinity surface plume that extends along the shelf, transported primarily north-westwards by the North Brazil Current (Muller-Karger et al, 1988;Geyer et al, 1996). There is only one rainy season in this region, from December to May (period of maximum flood of the Amazon River), and a less rainy season, from June to November (dry season or low flow period of the Amazon River) (Rao & Hada, 1990).…”

Microfitoplâncton da Plataforma Continental Amazônica Brasileira: Costa do Estado do Amapá – Brasil

“…Na área oceânica o deslocamento da pluma está relacionado com as correntes de fronteiras, que a deslocam para noroeste pela CNB. Em agosto e setembro, próximo de 7º N, a pluma sofre uma retro exão para leste (SILVA et al, 2009).…”