Ocean Currents, Dead Zones, and Global Warming

For the fifth year in a row, a dead zone has formed off the Oregon Coast. First documented in 2002, the dead zone has formed for each of the last five years - though in two of those years the zone got pushed off the ocean shelf. Marine biologist Dr. Lubchenco has studied the effected coastal region for the last 30 years. The dead zone first appeared in large scale in 2002. At that point, Lubchenco thought that the dead zone was an anomaly. The persistence of its reappearance may now signal a shift in ocean currents.

"Hypoxic conditions such as this have been documented in other nearshore upwelling ocean regions of the world," said Jack Barth, a professor of oceanography at OSU, "but never on the central Oregon coast."

"This system is normally healthy and productive," Lubchenco said. "But a change in ocean circulation appears to be shifting the system closer to a tipping point where the right conditions can kick it over the edge and into an hypoxia state. This coastal ecosystem off Oregon seems to be changing in a way we have never seen." (Science Daily, 8/10/06)

Proximally, the Oregon dead zone is erratic winds from a strong northerly flow. However, the winds are driven by ocean circulation.

I read five different articles on the Oregon dead zone, and saw largely the same information over and over again. Ocean currents, wind patterns, and global warming are in each of the reports. The natural question was "so what about those ocean currents." Anyone who has read much on climate change knows that ocean currents are a big deal. They "drive" the weather, and the climate around the globe. Under "normal" circumstances, the ocean conveyor belt is very consistent. However, there has been clear evidence for some time that ocean currents are changing.

Much of the focus on this change has been the dramatic changes in the North Atlantic current. Since the 1960's, and in an accelerating pattern, the North Atlantic current has slowed down as temperature differences have narrowed and salinity has declined (Ocean Change & Climate Institute).

In studies of seabed sediment layers, and ice cores from the poles, the picture that is emerging is that sudden changes in ocean circulation trigger abrupt climatic changes. The rapid atmospheric changes of the last 100 years, and dramatically accelerating in the last 35 years, are having their effect. The glaciers, and ice shelfs are melting at an accelerating rate, and that is dumping millions of gallons of fresh water into the ocean. Declining salinity as well as increasing temperature are slowing and weakening the current. It may also be shifting or defusing it. Such rapid changes in the current in the past have resulted in abrupt climate change (Science Daily, 6/25/04). "Abrupt" means a dramatic change in less than 10 years.

Given the new "pattern" of the dead zone off the Oregon coast, and its likely causes; given the increasing temperatures and heat records set over the last five years; given the accelerated melting of the ice sheets at the poles; one might ask "Are we in an "abrupt" change?"

Could the climate "trigger" have been hit five years ago? If so, and we are looking at a 10-12 year change cycle, then things could get very bad very fast.