Physical oceanography of the Amazon shelf

W. Rockwell Geyer, Robert C. Beardsley, Steven J. Lentz, Julio Candela, Richard Limeburner, William E Johns, Belmiro M. Castro, Ivan Dias Soares

Research output: Contribution to journalArticle

140 Citations (Scopus)

Abstract

The Amazon shelf is subject to energetic forcing from a number of different sources, including near-resonant semi-diurnal tides, large buoyancy flux from the Amazon River discharge, wind stress from the northeasterly tradewinds and strong along-shelf flow associated with the North Brazil Current. Although the large volume of river discharge produces a pronounced salinity anomaly, the water motions on the shelf are dominated by the other forcing factors . Tidal velocities of up to 200 cm s-1 are generally oriented in the cross-shelf direction. Tide-induced mixing influences the position and structure of the bottom salinity front that separates the well-mixed nearshore region from the stratified plume. High concentrations of suspended sediment trapped along the frontal zone increase the stability of the tidal boundary layer and thus reduce the bottom stress. At subtidal frequencies, motion is primarily along-shelf toward the northwest, both in the plume and in the ambient, high-salinity water of the outer-shelf. The plume is generally 5-10 m thick, with a salinity of 20-30 psu. The along-shelf velocity within the plume varies as a function of the along-shelf wind stress. This variability results in large temporal variations in plume structure and freshwater content on the shelf. The net northwestward motion of the Amazon plume and of the ambient shelf water appears to be the result of a large-scale pressure gradient associated with the North Brazil Current system.

Original languageEnglish (US)
Pages (from-to)575-616
Number of pages42
JournalContinental Shelf Research
Volume16
Issue number5-6
StatePublished - 1996

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physical oceanography
oceanography
water salinity
tides
plume
salinity
Amazon River
Brazil
temporal variation
river discharge
wind stress
rivers
semidiurnal tide
bottom stress
water
pressure gradient
suspended sediment
buoyancy
tide
energetics

ASJC Scopus subject areas

  • Aquatic Science
  • Geology
  • Oceanography

Cite this

Geyer, W. R., Beardsley, R. C., Lentz, S. J., Candela, J., Limeburner, R., Johns, W. E., ... Soares, I. D. (1996). Physical oceanography of the Amazon shelf. Continental Shelf Research, 16(5-6), 575-616.

Physical oceanography of the Amazon shelf. / Geyer, W. Rockwell; Beardsley, Robert C.; Lentz, Steven J.; Candela, Julio; Limeburner, Richard; Johns, William E; Castro, Belmiro M.; Soares, Ivan Dias.

In: Continental Shelf Research, Vol. 16, No. 5-6, 1996, p. 575-616.

Research output: Contribution to journalArticle

Geyer, WR, Beardsley, RC, Lentz, SJ, Candela, J, Limeburner, R, Johns, WE, Castro, BM & Soares, ID 1996, 'Physical oceanography of the Amazon shelf', Continental Shelf Research, vol. 16, no. 5-6, pp. 575-616.
Geyer WR, Beardsley RC, Lentz SJ, Candela J, Limeburner R, Johns WE et al. Physical oceanography of the Amazon shelf. Continental Shelf Research. 1996;16(5-6):575-616.
Geyer, W. Rockwell ; Beardsley, Robert C. ; Lentz, Steven J. ; Candela, Julio ; Limeburner, Richard ; Johns, William E ; Castro, Belmiro M. ; Soares, Ivan Dias. / Physical oceanography of the Amazon shelf. In: Continental Shelf Research. 1996 ; Vol. 16, No. 5-6. pp. 575-616.
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