Estuaries and Coasts

, Volume 35, Issue 2, pp 665–681 | Cite as

Frontogenesis and Frontal Progression of a Trapping-Generated Estuarine Convergence Front and Its Influence on Mixing and Stratification

  • Sarah N. Giddings
  • Derek A. Fong
  • Stephen G. Monismith
  • C. Chris Chickadel
  • Kathleen A. Edwards
  • William J. Plant
  • Bing Wang
  • Oliver B. Fringer
  • Alexander R. Horner-Devine
  • Andrew T. Jessup
Article

Abstract

Estuarine fronts are well known to influence transport of waterborne constituents such as phytoplankton and sediment, yet due to their ephemeral nature, capturing the physical driving mechanisms and their influence on stratification and mixing is difficult. We investigate a repetitive estuarine frontal feature in the Snohomish River Estuary that results from complex bathymetric shoal/channel interactions. In particular, we highlight a trapping mechanism by which mid-density water trapped over intertidal mudflats converges with dense water in the main channel forming a sharp front. The frontal density interface is maintained via convergent transverse circulation driven by the competition of lateral baroclinic and centrifugal forcing. The frontal presence and propagation give rise to spatial and temporal variations in stratification and vertical mixing. Importantly, this front leads to enhanced stratification and suppressed vertical mixing at the end of the large flood tide, in contrast to what is found in many estuarine systems. The observed mechanism fits within the broader context of frontogenesis mechanisms in which varying bathymetry drives lateral convergence and baroclinic forcing. We expect similar trapping-generated fronts may occur in a wide variety of estuaries with shoal/channel morphology and/or braided channels and will similarly influence stratification, mixing, and transport.

Keywords

Front Frontogenesis Trapping Convergence front Lateral circulation 

Supplementary material

12237_2011_9453_MOESM1_ESM.doc (8 mb)
ESM 1(DOC 8187 kb)

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Copyright information

© Coastal and Estuarine Research Federation 2011

Authors and Affiliations

  • Sarah N. Giddings
    • 1
  • Derek A. Fong
    • 2
  • Stephen G. Monismith
    • 2
  • C. Chris Chickadel
    • 3
  • Kathleen A. Edwards
    • 4
  • William J. Plant
    • 3
  • Bing Wang
    • 2
  • Oliver B. Fringer
    • 2
  • Alexander R. Horner-Devine
    • 5
  • Andrew T. Jessup
    • 3
  1. 1.School of OceanographyUniversity of WashingtonSeattleUSA
  2. 2.Department Civil and Environmental EngineeringStanford UniversityStanfordUSA
  3. 3.Applied Physics LaboratoryUniversity of WashingtonSeattleUSA
  4. 4.Ocean Power TechnologiesPenningtonUSA
  5. 5.Department Civil and Environmental EngineeringUniversity of WashingtonSeattleUSA

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