Day of Month, June 2003 
Figure 3.2.7. Bakun upwelling index for 36° N latitude for the West Coast in June 
2003. 
cable problem resulted in a failure to collect DO data from many stations along 
the north and central Oregon coast. An estimated 94.3% of the shelf area had a 
bottom-water DO concentration < 4.8 mg/L and 6.6% of the area (6 of the 140 
stations where DO data were available) had a bottom-water DO concentration < 
2.3 mg/L. There was no geographic concentration of stations with bottom-water 
DO in this < 2.3 mg/L range (Figure 3.2.9). Stations with bottom-water DO > 4.8 
mg/L were concentrated at the extreme southern and northern ends of the survey 
region. Mean bottom-water DO concentrations were lower at Oregon stations 
than for Washington and California locations (Figure 3.2.10 A). Mean bottom DO 
was lower at the CA NMS stations than at the CA non-NMS stations, presumably 
resulting from the strong upwelling occurring during the sampling period that 
moved deeper low-DO water into the area (Figure 3.2.10 B). 
Flypoxia on the continental shelf of the West Coast appears to be 
associated with upwelling conditions in the region, while severe hypoxic events in 
inshore shelf areas (< 70 m) may be associated with changes in cross-shelf 
current patterns (Grantham et al. 2004). It appears that the frequency of shelf 
hypoxia has increased in recent years, and that shelf anoxia has now been 
observed at inner-shelf stations within 2 km of the surf zone (Chan et al. 2008). 
38 
