The formation of dense water masses at polar regions has been largely infl uenced by climate changes arising from global warming. In this context, based on ensemble simulations with a coupled model we evaluate the meridional shift of a climate signal (i.e., a cold and fresh water input pulse generated from melting of positive Antarctic sea ice (ASI) extremes) towards the Tropical Atlantic Ocean (TAO). This oceanic signal propagated from Southern Ocean towards the equator through the upper layers due to an increase in its buoyance. Its northward shift has given by the Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) fl ows, that inject cold and fresh mode/intermediate waters from into subtropical basin. The signal has reached low latitudes through the equatorial upwelling and spreads out southwards, through the upper branch of southern subtropical gyre. We concluded that 10 years of coupled simulations was enough time to propagate the climate signal generated by ASI positive extremes melting, which reached TOA around 2 year later. The oceanic connection between Southern Ocean and TAO is indeed established within the timescale analyzed in the study (10 years). Nonetheless, the period needed to completely dissipate the disturbance generated from ASI seems to be longer.
Este estudo objetiva a caracterização morfodinâmica e sedimentar das praias do Banho e Caúra, localizadas no município de São José de Ribamar -MA (2°33'25"-2°33'52"S e 44°02'21" W -44° 03'13" W). A morfodinâmica e a geologia foram analisadas nas duas praias, em campanhas realizadas no período de estiagem (outubro/2016). Perfis perpendiculares à linha de costa foram monitorados durante o ciclo de marés de sizígia nas duas praias e foram coletados sedimentos para a classificação dos grãos e permeabilidade. A direção da corrente de deriva litorânea foi avaliada, utilizando-se como traçador um corante orgânico vermelho. Os resultados mostraram uma maior extensão de sedimentos na praia do Banho, com uma antepraia (foreshore) de 624 metros de perfil praial, enquanto a praia do Caúra revelou um perfil praial correspondente a uma extensão de 105 m, com um avanço da maré em vários pontos, bem como a presença de calhas, bancos de areias e falésias. A granulometria das praias variou de areia média a areia fina, para as praias do Banho e Caúra, respectivamente. O ensaio de permeabilidade do sedimento mostrou uma relação inversa com a granulometria. A praia do Banho obteve menor coeficiente de permeabilidade (k) e maior classe textural (areia média), enquanto a praia do Caúra registrou maior coeficiente (k) e menor classe textural (areia fina). O experimento de verificação da deriva litorânea na praia do Banho, em condição de maré vazante, mostrou um escoamento paralelo à linha de costa com uma velocidade de 0,10 m.s -1 .
The objective of this research was to characterize the distribution of dissolved nutrients at six sampling stations in the estuary of the Anil River (ARE) and characterize the bottom sediment. The study area is influenced by a tropical climate and semidiurnal macrotidal regime. Sampling of the surface water and sediment was performed in the main channel at six sampling stations distributed along the estuary in the rainy period (May 9th) and dry period (October 5th) during the spring. Physical variables were collected with the aid of a HANNA HI-8424 multi-parameter probe (water temperature, salinity, pH, dissolved oxygen, and turbidity) and YSI CTD (conductivity, temperature, and depth) probe. A van Veen dredge was used for the collection of bottom sediment from the main channel. The sedimentological results were heterogeneous. Grain size ranged from very fine to medium sand. Dissolved nutrients in the ARE had different sources depending on the season. Continental and fluvial inputs, evidenced by salinity values, governed the distribution of nutrients in the rainy period (January to June), whereas nutrient concentrations were related to the recycling of organic material in the estuary in the dry season (July to December). The considerable presence of sand in the main channel indicates that the sediments available in ARE are exposed to intense hydrodynamics. The distribution of nutrients and the grain size revealed the occurrence of different sources in the estuary according to the rainfall regime and the intense hydrodynamics of tidal currents (semidiurnal macrotidal).
Keywords: dissolved nutrients, estuarine environment, sedimentology.
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