Publication Date:
2022-05-25
Description:
Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2009
Description:
Mechanisms for the tidal component of salt flux in the Hudson River estuary are
investigated using a 3D numerical model. Variations with river discharge, fortnightly
tidal forcing, and along channel variability are explored. Four river discharge conditions
were considered: 1200 m3 s-1, 600 m3 s-1, 300 m3 s-1, 150 m3 s-1. Tide-induced residual
salt flux was found to be variable along the channel, with locations of counter-gradient
flux during both neap and spring tide. The magnitude of tidal salt flux scales with the
river flow and has no clear dependence on the spring-neap tidal forcing. The diffusive
fraction, ν, has a value of -0.25 to 0.46 in the lower estuary, increasing to -0.23 to 1 near
the head of salt. The phase lag between tidal salinity and velocity is analyzed at three
cross-sections with: large positive, negative, and weak tidal salt flux. The composite
Froude number, G2, is calculated along the channel and indicates nearly ubiquitous
supercritical flow for maximum flood and ebb during both neap and spring tides.
Subcritical flow occurs during slack water and at geographically locked locations during
neap floods. Application of two-layer, frictional hydraulic theory reveals how variations
in channel width and depth generate tidal asymmetries in cross-sectional salinity, the key
ingredient of tidal salt flux.
Keywords:
Salinity
;
Tides
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
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