AGU Ocean Sciences Meeting (Feb. 2002) COAST abstracts:

• Ashe et al.
  
• Bane et al.
  
• Barth et al.
  
• Coletti et al.
  
• Haines et al.
  
• Karp-Boss et al.
  
• Kosro et al.
  
• Kurapov et al.
  
• Okeefe et al.
  
• Ott et al.
  
• Perlin et al.
  
• Ruttenberg et al.
  
• Sutor et al.
  

OS41O-02

The Coastal Ocean Response to Summertime Downwelling Favorable
Winds off Oregon

Jack A. Barth and Stephen D. Pierce

College of Oceanic and Atmospheric Sciences, Oregon State University 

On the strongly wind-driven continental margin of the northeast
Pacific ocean, seasonal upwelling drives high biological
productivity.  During the summer when winds are generally upwelling
favorable, there are periods when the winds are weak ("relaxed")
or strongly downwelling favorable.  During June 2000 and again
in August 2001, the oceanic and ecosystem response off Oregon to
strong summertime downwelling was observed.  During the downwelling
event, northward winds lasted 3-4 days and reached speeds of up
to 40 knots.  The surface layer warmed by about 4C over the entire
continental shelf as warm oceanic surface water was advected onshore.
The southward upwelling jet and the accompanying tilted isopycnals
that existed before the downwelling event persisted, but were located
over the mid- to outer shelf.  Downwelled isopycnals were found
within 15 km of the coast.  Northward currents in excess of 0.2 m/s
were found inshore of the 70 m isobath and were continuous over the
entire study region (130 km alongshore).  Prior to the downwelling
event, chlorophyll fluorescence was confined to the upper 20 m and
was highest adjacent to the coast.  During strong northward winds,
high chlorophyll was downwelled with the isopycnals near the coast.
Chlorophyll was distributed throughout the water column in water
depths less than about 70 m.  Details of the time evolution of the
coupled physical and biological response to summertime downwelling
will be presented.  The response to strong downwelling favorable
winds is compared with that accompanying wind relaxation.  In the
latter, N-S pressure gradients, e.g. as created by flow-topography
interaction, can drive inshore flow northward, but without the
accompanying downwelled isopycnals.

Additional resources: 
http://damp.oce.orst.edu/coast