Hypoxic Conditions Prior to 2002

The geographic extent of known hypoxia in 2006 and 2007. Light blue shows the  extent of hypoxia (<1.4 ml/l) and purple shows the region of severe hypoxia (<0.5  ml/l). Waters closest to the shore remain high in oxygen due to breaking waves.  Dots represent sampling sites. Data made available by PISCO and NOAA-Fisheries, NWFSC. (download high-res PDF)

Prior to 2002, dead zone events had not been reported in the near-shore waters off the Oregon and Washington coasts.

It is important to note that low-oxygen water is a normal feature in deep, offshore waters. Fishermen and scientists both know that this low-oxygen water can be present in the summertime on the outer portions of the continental shelf and slope. What is different in the last several years is the presence of low-oxygen water in the inner shelf (less than 50 m (165’) of water).

An analysis of historical oxygen data from 1950 to 2006 shows that conditions off the Oregon coast have changed significantly since 2000. (Chan, F., J. A.Barth, J. Lubchenco, A. Kirincich, H. Weeks, W.T. Peterson, and B. A. Menge. 2008.  Emergence of Anoxia in the California Current Large Marine Ecosystem. Science 15 February 2008 vol 319.  www.sciencemag.org)