Global Warming to Create "Permanent" Ocean Dead Zones?

January 28, 2009

Fish and other marine life could be left gasping for breath in oxygen-poor oceans for thousands of years to come if global warming continues unchecked, scientists warn in a new study.

While previous studies have established a link between climate change and low-oxygen areas known as "dead zones," new computer simulations by Danish researchers suggest the dead zones could persist for millennia and lead to a considerable purge and restructuring of ocean life.

"Any increase in dead zones from global warming will last for thousands of years. They will be a permanent fixture" of our oceans, said lead researcher Gary Shaffer of the University of Copenhagen.

The new model tracked the effects of global warming on ocean dead zones in the eastern Pacific and northern Indian oceans for the next 100,000 years.

Dead zones currently make up less than 2 percent of the world's ocean volume. The model predicts that global warming could cause dead zones to grow by a factor of ten or more by the year 2100.

In the worst-case scenario, dead zones could encompass more than a fifth of the world's oceans, the team says.

(Related: "Ocean Dead Zones Growing; May Be Linked to Warming" [May 1, 2008].)

Waves of Death

While many dead zones today are transient and reversible, those expanded by greenhouse gases such as carbon dioxide would last for millennia, Shaffer said.

"Quite a bit of the carbon dioxide emitted by human activity into the atmosphere will stay there for tens of thousands of years."

"Thus global warming, ocean warming, and oxygen depletion will also have this long time scale," he said.

According to the model, global warming will reduce the oceans' ability to store oxygen while simultaneously decreasing the amount of oxygen available in the ocean depths.

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