Fall AGU Meeting (Dec. 2002) COAST abstracts:

• Allen
  
• Bane et al.
  
• Barth et al.
  
• Carney et al.
  
• Couch et al.
  
• Cowles et al.
  
• Dale et al.
  
• Durski et al.
  
• Egbert et al.
  
• Gan et al.
  
• Hales et al.
  
• Kosro et al.
  
• Kuebel et al.
  
• Kurapov et al.
  
• Perlin et al.
  
• Pierce et al.
  
• Ruttenberg et al.
  
• Samelson
  
• Spitz et al.
  
• Wheeler
  

Abstracts should be cited as:

EOS Trans. AGU, 83 (47),
Fall Meet. Suppl.,
Abstract XXXXX-XX, 2002

OS62A-0228

Modeling study of upwelling processes over the Oregon shelf

J Gan and J S Allen

Time-dependent, three dimensional circulation on the continental
shelf off Oregon is studied using the Princeton Ocean Model
(POM). The objective is to investigate the flow dynamics, the
across-shelf transport, and the nature of the small scale turbulence
field associated with the temporal and spatial variability of
upwelling on the Oregon shelf during summer 2001. The study applies
forcing from observed winds and heat flux for May-August 2001. Model
variables compare favorably with current, temperature, hydrographic
and turbulence measurements from the 2001 Coastal Ocean Advances
in Shelf Transport (COAST) field experiment. The results show
that strong offshore transport occurs in the surface/bottom layers
near the coast and over Heceta Bank during upwelling/relaxation,
respectively. Opposite conditions occur, however, onshore of the
100 m isobath over the south-east region of the bank where northward
currents associated with a cyclonic circulation are found. Relatively
large values of across-barotropic- streamline transport are found
at the outer edge of the bank along the 200 m isobath and off
Cape Blanco. Analysis of the balance of terms in the equation for
potential temperature reveals that decreasing water temperatures
over the bank are caused mainly by across-shelf and vertical
advection. Alongshore advection, however, leads to low-density water
around the southeast edge of the bank. Relatively large values of
turbulent kinetic energy (TKE) are found in both the surface and the
bottom boundary layers, with the higher intensity near the coast and
over the bank during upwelling. As the upwelling wind relaxes, the
TKE weakens quickly at the surface while high values remain near the
bottom during the development of northward currents as part of the
pressure gradient driven relaxation response.  In the time-averaged
alongshore momentum equation, strong nonlinear advective effects
balance a northward ageostrophic pressure gradient force over the
bank contributing to the formation of a local cyclonic circulation.