Oceans reaching tipping points

WASHINGTON — A sobering new report warns that the oceans face a "fundamental and irreversible ecological transformation" not seen in millions of years as greenhouse gases and climate change already have affected temperature, acidity, sea and oxygen levels, the food chain and possibly major currents that could alter global weather.

The report, in Science magazine, brings together dozens of studies that collectively paint a dismal picture of deteriorating ocean health.

"This is further evidence we are well on our way to the next great extinction event," said Ove Hoegh-Guldberg, the director of the Global Change Institute at the University of Queensland in Australia and a co-author of the report.

John Bruno, an associate professor of marine sciences at the University of North Carolina at Chapel Hill and the report's other co-author, isn't quite as alarmist, but he's equally concerned.

"We are becoming increasingly certain that the world's marine ecosystems are reaching tipping points," Bruno said, adding, "We really have no power or model to foresee" the impact.

Volcanic activity and large meteorite strikes in the past have "resulted in hostile conditions that have increased extinction rates and driven ecosystem collapse," the report says. "There is now overwhelming evidence human activities are driving rapid changes on a scale similar to these past events.

"Many of these changes are already occurring within the world's oceans with serious consequences likely over the coming years."

"Although our comprehension of how this variability will change over the coming decades remains uncertain, the steady increase in heat content in the ocean and atmosphere are likely to have profound influences on the strength, direction and behavior of the world's major current systems," the report says.

"It's a lot worse than the public thinks," said Nate Mantua, an associate research professor at the University of Washington's Climate Impacts Group.

Mantua, who's read the report, said it was clear what was causing the oceans' problems: greenhouse gases. "It is not a mystery," he said.