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Tidal exchange in a choked coastal lagoon : A study of Mundaú Lagoon in northeastern Brazil

de Brito, Almir Nunes LU ; Fragoso, Carlos Ruberto and Larson, Magnus LU (2018) In Regional Studies in Marine Science 17. p.133-142
Abstract

Changes in the inlet morphology of choked coastal lagoons often restrict the water exchange with the sea, making them vulnerable to pollution events and eutrophication processes. In this study, the importance of tides for the water exchange was investigated in Mundaú Lagoon, which is a choked lagoon located in northeastern Brazil that has a very dynamic inlet and channel system. The analysis was carried out for critical scenarios during the dry season when the river flow to the lagoon decreases markedly. The concepts of integrated flushing time and spatially distributed residence time scales were applied using a Lagrangian particle tracking approach coupled with a hydrodynamic model. The flushing time of Mundaú Lagoon was estimated to... (More)

Changes in the inlet morphology of choked coastal lagoons often restrict the water exchange with the sea, making them vulnerable to pollution events and eutrophication processes. In this study, the importance of tides for the water exchange was investigated in Mundaú Lagoon, which is a choked lagoon located in northeastern Brazil that has a very dynamic inlet and channel system. The analysis was carried out for critical scenarios during the dry season when the river flow to the lagoon decreases markedly. The concepts of integrated flushing time and spatially distributed residence time scales were applied using a Lagrangian particle tracking approach coupled with a hydrodynamic model. The flushing time of Mundaú Lagoon was estimated to be 12.6 days during neap tide and 5.7 days during spring tide, including a return flow factor. Employing an e-folding form, the corresponding value was calculated to be 64 and 54 days for particles allowed and not allowed to return to the lagoon, respectively. The spring tides were responsible for the most pronounced water exchange in the Mundaú Lagoon. Different particles release times displayed the effect of the initial tidal conditions on the flushing time; lower exchange times were estimated for releases during ebb tides and spring tides. The integrated estimation of the water exchange when imposing a scenario of most frequent wind conditions indicated a considerable delay caused by this forcing, increasing the flushing time up to 23 days. Another observed effect of the wind was a spatial redistribution of the tidal exchange in the lagoon into different zones with similar residence time.

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Contribution to journal
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published
subject
keywords
Brazil, Choked coastal lagoon, Exchange time scales, Mundaú lagoon, Numerical modeling, Particle transport, Residence time
in
Regional Studies in Marine Science
volume
17
pages
10 pages
external identifiers
  • scopus:85039728152
DOI
language
English
LU publication?
yes
id
d369a60c-385a-421b-af3e-74d35f9b7291
date added to LUP
2018-01-09 11:08:00
date last changed
2018-05-29 10:10:47
@article{d369a60c-385a-421b-af3e-74d35f9b7291,
  abstract     = {<p>Changes in the inlet morphology of choked coastal lagoons often restrict the water exchange with the sea, making them vulnerable to pollution events and eutrophication processes. In this study, the importance of tides for the water exchange was investigated in Mundaú Lagoon, which is a choked lagoon located in northeastern Brazil that has a very dynamic inlet and channel system. The analysis was carried out for critical scenarios during the dry season when the river flow to the lagoon decreases markedly. The concepts of integrated flushing time and spatially distributed residence time scales were applied using a Lagrangian particle tracking approach coupled with a hydrodynamic model. The flushing time of Mundaú Lagoon was estimated to be 12.6 days during neap tide and 5.7 days during spring tide, including a return flow factor. Employing an e-folding form, the corresponding value was calculated to be 64 and 54 days for particles allowed and not allowed to return to the lagoon, respectively. The spring tides were responsible for the most pronounced water exchange in the Mundaú Lagoon. Different particles release times displayed the effect of the initial tidal conditions on the flushing time; lower exchange times were estimated for releases during ebb tides and spring tides. The integrated estimation of the water exchange when imposing a scenario of most frequent wind conditions indicated a considerable delay caused by this forcing, increasing the flushing time up to 23 days. Another observed effect of the wind was a spatial redistribution of the tidal exchange in the lagoon into different zones with similar residence time.</p>},
  author       = {de Brito, Almir Nunes and Fragoso, Carlos Ruberto and Larson, Magnus},
  keyword      = {Brazil,Choked coastal lagoon,Exchange time scales,Mundaú lagoon,Numerical modeling,Particle transport,Residence time},
  language     = {eng},
  month        = {01},
  pages        = {133--142},
  series       = {Regional Studies in Marine Science},
  title        = {Tidal exchange in a choked coastal lagoon : A study of Mundaú Lagoon in northeastern Brazil},
  url          = {http://dx.doi.org/},
  volume       = {17},
  year         = {2018},
}