Dead Zone Off Oregon Coast Needs Storms to Break Up

An area of ocean bottom stretching at least 70 miles along the Continental Shelf off Oregon has such low oxygen levels that fish and crabs are unable to survive. The condition is caused by what scientist are calling "classic global warming conditions" that create northerly winds and bring cold, nutrient rich Arctic waters upwelling to the surface where they feed plankton. The plankton die when the wind stalls and fall to the bottom, where they are consumed by bacteria, which use up all the oxygen. October storms are needed to break up this cycle.

Scientists first noticed a dead zone off Newport in 2002 and traced it to a rare influx of cold water rich in nutrients and low in oxygen that had migrated from the Arctic.

Each year since then, they have returned in the summer, but these have been caused by unusually intense bursts of northerly winds that cause the ocean water to turn over, bringing nutrients up from the bottom and feeding an explosion of tiny organisms known as phytoplankton.

During calm periods, the phytoplankton die for lack of food and fall to the ocean bottom, where they are consumed by bacteria, which use up the oxygen.

The wind patterns responsible for the dead zones are consistent with what is expected with global warming: warmer temperatures on land strengthen a low pressure area that draws more air in from the cooler ocean, creating the winds that set up the upwelling, and driving the dead zone close to shore.

link

This does not bode well for the marine fisheries and economies dependent on the sea life in the area. The ocean bottom in this "dead zone" is basically uninhabitable for sea life due to acute oxygen depletion. The condition is likely to escalate cyclically if average temperatures over land in the area continue to rise.