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Estuaries

, Volume 26, Issue 6, pp 1437–1449 | Cite as

On the linkages among density, flow, and bathymetry gradients at the entrance to the Chesapeake Bay

  • Arnoldo Valle-Levinson
  • William C. Boicourt
  • Michael R. Roman
Article

Abstract

Linkages among density, flow, and bathymetry gradients were explored at the entrance to the Chesapeake Bay with underway measurements of density and flow profiles. Four tidal cycles were sampled along a transect that crossed the bay entrance during cruises in April–May of 1997 and in July of 1997. The April–May cruise coincided with neap tides, while the July cruise occurred during spring tides. The bathymetry of the bay entrance transect featured a broad Chesapeake Channel, 8 km wide and 17 m deep, and a narrow North Channel, 2 km wide and 14 m deep. The two channels were separated by an area with typical depths of 7 m. Linkages among flows, bathymetry, and water density were best established over the North Channel during both cruises. Over this channel, greatest convergence rates alternated from the left (looking into the estuary) slope of the channel during ebb to the right slope during flood as a result of the coupling between bathymetry and tidal flow through bottom friction. These convergences were linked to the strongest transverse shears in the along-estuary tidal flow and to the appearance of salinity fronts, most markedly during ebb periods. In the wide channel, the Chesapeake Channel, frontogenesis mechanisms over the northern slope of the channel were similar to those in the North Channel only in July, when buoyancy was relatively weak and tidal forcing was relatively strong. In April–May, when buoyancy was relatively large and tidal forcing was relatively weak, the recurrence of fronts over the same northern slope of the Chesapeake Channel was independent of the tidal phase. The distinct frontogenesis in the Chesapeake Channel during the increased buoyancy period was attributed to a strong pycnocline that insulated the surface tidal flow from the effects of bottom friction, which tends to decrease the strength of the tidal flow over relatively shallow areas.

Keywords

Transverse Shear Neap Tide Bottom Friction Absolute Vorticity Salinity Front 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Estuarine Research Federation 2003

Authors and Affiliations

  • Arnoldo Valle-Levinson
    • 1
  • William C. Boicourt
    • 2
  • Michael R. Roman
    • 2
  1. 1.Center for Coastal Physical Oceanography, Department of Ocean, Earth, and Atmospheric SciencesOld Dominion UniversityNorfolk
  2. 2.Horn Point LaboratoryUniversity of Maryland Center for Environmental ScienceCambridge

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