Seasonal variability and estuary-shelf interactions in circulation dynamics of a river-dominated estuary

Arun Chawla, David A. Jay, Antonio Baptista, Michael Wilkin, Charles Seaton

Research output: Contribution to journalArticle

48 Citations (Scopus)

Abstract

The long-term response of circulation processes to external forcing has been quantified for the Columbia River estuary using in situ data from an existing coastal observatory. Circulation patterns were determined from four Acoustic Doppler Profilers (ADP) and several conductivity-temperature sensors placed in the two main channels. Because of the very strong river discharge, baroclinic processes play a crucial role in the circulation dynamics, and the interaction of the tidal and subtidal baroclinic pressure gradients plays a major role in structuring the velocity field. The input of river flow and the resulting low-frequency flow dynamics in the two channels are quite distinct. Current and salinity data were analyzed on two time scales-subtidal (or residual) and tidal (both diurnal and semidiurnal components). The residual currents in both channels usually showed a classical two-layer baroclinic circulation system with inflow at the bottom and outflow near the surface. However, this two-layer system is transient and breaks down under strong discharge and tidal conditions because of enhanced vertical mixing. Influence of shelf winds on estuarine processes was also observed via the interactions with upwelling and downwelling processes and coastal plume transport. The transient nature of residual inflow affects the long-term transport characteristics of the estuary. Effects of vertical mixing could also be seen at the tidal time scale. Tidal velocities were separated into their diurnal and semidiurnal components using continuous wavelet transforms to account for the nonstationary nature of velocity amplitudes. The vertical structure of velocity amplitudes were considerably altered by baroclinic gradients. This was particularly true for the diurnal components, where tidal asymmetry led to stronger tidal velocities near the bottom.

Original languageEnglish (US)
Pages (from-to)269-288
Number of pages20
JournalEstuaries and Coasts
Volume31
Issue number2
DOIs
StatePublished - Apr 2008

Fingerprint

estuaries
seasonal variation
estuary
rivers
river
vertical mixing
inflow
timescale
Columbia River
profiler
downwelling
river discharge
pressure gradient
river flow
wavelet
acoustics
asymmetry
upwelling
transform
outflow

Keywords

  • Baroclinic circulation
  • Circulation dynamics
  • Mixing processes
  • River-dominated estuary
  • Salt transport
  • Seasonal variability
  • Tidal dynamics
  • Wavelet transforms

ASJC Scopus subject areas

  • Aquatic Science
  • Ecology, Evolution, Behavior and Systematics
  • Ecology

Cite this

Seasonal variability and estuary-shelf interactions in circulation dynamics of a river-dominated estuary. / Chawla, Arun; Jay, David A.; Baptista, Antonio; Wilkin, Michael; Seaton, Charles.

In: Estuaries and Coasts, Vol. 31, No. 2, 04.2008, p. 269-288.

Research output: Contribution to journalArticle

Chawla, Arun ; Jay, David A. ; Baptista, Antonio ; Wilkin, Michael ; Seaton, Charles. / Seasonal variability and estuary-shelf interactions in circulation dynamics of a river-dominated estuary. In: Estuaries and Coasts. 2008 ; Vol. 31, No. 2. pp. 269-288.
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