Ocean 'dead zones' begot by warming

A new study has linked low-oxygen 'dead zones' in North Pacific to the past ocean warming.

The study has found a link between abrupt ocean warming at the end of the last ice age and the sudden onset of low-oxygen, or hypoxic, conditions that led to the vast marine dead zones.

This works tackles a long-standing debate about what causes expansion of Oxygen Minimum Zones, also known as dead zones, in the oceans, said Candace Major, adding that the results demonstrate a link between warming surface temperatures and dead zones at great depths. The findings also show that the response time between warming and dead zone expansion is quite fast.

Large-scale warming events at about 14,700, and again 11,500, years ago occurred rapidly and triggered loss of oxygen in the North Pacific, raising concern that low-oxygen areas will expand again as the oceans warm in the future.

Anomalous warmth that occurred recently in the Northeastern Pacific Ocean and the Bering Sea, dubbed "The Blob," is of a scale similar to events documented in the geologic record.

The study is published in the journal Nature.