Seasonal characteristics of hydrography, turbulence and dispersion near Ilha Grande (RJ), Brazil, based on R/V "Prof. W. Besnard" data

Abstract

Seasonal differences in sigma-t (1.8)3 temperature (4.0ºC) and salinity (0.9‰) were observed during February/June 1976 in the vicinity of Ilha Grande off the coast of Brazil Estimates of static and dynamic stability were made through the calculation of Brunt-Vaisala frequencies and Richardson numbers, respectively. Both static and dynamic stability values were larger in February than in June for the same location and suggest a greater column stability in February than in June. Stations located in the northern and western channels of Ilha Grande, however, contained greater density reversals than to the east of the Island. Small scale dispersion studies were made using Rhomamine B dye to determine horizontal diffusion coefficients (K) east of the Island and in an embayment of the Island. The estimate for K was 9X10³ cm² s-1 east of the Island, about 2.6 times greater than the value estimated for the protected embayment.

ARTIGOS

Seasonal characteristics of hydrography, turbulence and dispersion near Ilha Grande (RJ), Brazil, based on R/V "Prof. W. Besnard" data

Yoshimine Ikeda^I; Merritt Raymond Stevenson^II

^IInstituto Oceanográfico da Universidade de São Paulo

^IIInstituto de Pesquisas Espaciais, CNPq

SYNOPSIS

Seasonal differences in sigma-t (1.8)3 temperature (4.0ºC) and salinity (0.9‰) were observed during February/June 1976 in the vicinity of Ilha Grande off the coast of Brazil Estimates of static and dynamic stability were made through the calculation of Brunt-Vaisala frequencies and Richardson numbers, respectively. Both static and dynamic stability values were larger in February than in June for the same location and suggest a greater column stability in February than in June. Stations located in the northern and western channels of Ilha Grande, however, contained greater density reversals than to the east of the Island. Small scale dispersion studies were made using Rhomamine B dye to determine horizontal diffusion coefficients (K) east of the Island and in an embayment of the Island. The estimate for K was 9X10³ cm² s^-1 east of the Island, about 2.6 times greater than the value estimated for the protected embayment.

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Acknowledgments

The basic data and preparation of this paper was supported by the OAS Program: Programa Multinacional de Ciencias do Mar, Project "Integrado para o Uso e Exploração Racional do Meio Ambiente Marinho/Subprojeto Biologia da Pesca" - FINEP and São Paulo University. Ours thanks to Mr. Marco Antonio Montalban and Mr. Osmar M. P. Campos for the drawings and to Miss Marilza Correia and Ms. Eliete A. O. Maciel for typing the manuscript. Support for Merrit Stevenson was provided by the Instituto de Pesquisas Espaciais/CNPq, São José dos Campos, SP, and it is acknowledged with appreciation.

(Manuscript received on 15/Oct./1979; accepted on 25/Nov./1981)

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Publication Dates

• Publication in this collection
  04 June 2012
• Date of issue
  1982

History

• Accepted
  25 Nov 1981
• Received
  15 Oct 1979