Dynamics of river plumes in the South Brazilian Bight and South Brazil
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Dynamics of river plumes in the South Brazilian Bight and South Brazil Martinho Marta-Almeida1,2
· Anna Dalbosco3 · David Franco3 · Manuel Ruiz-Villarreal2
Received: 25 December 2018 / Accepted: 6 July 2020 © The Author(s) 2020
Abstract The plumes from the rivers of the South Brazilian Bight (SBB) and South Brazil (SB) were studied using a realistic model configuration. River plume variability on continental shelves is driven by the input of river runoff into the shelf, by wind variability, and also by ambient currents and its seasonal variability, especially the Brazil Current, which are realistically modelled in this study. It is presented a simulation of 4 years using a nested configuration, which allows resolving the region around Florian´opolis with very high resolution (∼150 m). The dispersion of river plumes was assessed not only with the hydrodynamical model results but also by using passive tracers whose dynamics was analyzed seasonally. Several dyes were released together with the river discharges. This approach allowed calculating the depths of the riverine freshwater, and the resulting regions affected by the plumes. Northward intrusions of waters from the southern region, under the potential influence of the distant La Plata river plume, were evaluated with a Lagrangian approach. The local river plumes are confined to the inner shelf, except south of 30◦ S where discharges from Lagoa dos Patos disperse over the shelf in the spring and summer. The Brazil Current flowing southward over the slope prevents the river plumes from interaction with oceanic mesoscale dynamics. The river plumes are, thus, mainly controlled by the wind forcing. The plumes from SBB are able to disperse until SB following the southward wind regime typical of the summer. And both the SB and La Plata river plumes are also able to reach SBB, forced by the northward wind typical of the winter season, until the latitude of 25.5◦ S. A low salinity belt (below 35) is present along the coastal region of SB and SBB year-round, supported by contributions from both the large and small rivers. The interaction between the different plumes influences the dispersion patterns, shielding the Florian´polis coastal region from plumes of distant rivers, and dispersing the plume of SBB rivers away from Santa Catarina Island as it disperses southward during the summer months. Keywords South Brazilian Bight · South Brazil · Florian´opolis · River plumes dispersion · River plumes interaction · 2-way model nesting
1 Introduction Florian´opolis is located in the Brazillian coastal region around 27◦ S, in the state of Santa Catarina. It consists of a main island, also called Santa Catarina; a continental
Responsible Editor: Ricardo de Camargo This article is part of the Topical Collection on the 11th International Workshop on Modeling the Ocean (IWMO), Wuxi, China, 17–20 June 2019 Martinho Marta-Almeida
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Extended author information available on the last page of the article.
part; and several small islands (Fig. 1). The region has an imp
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