World’s largest ocean dead zone may shrink as Earth warms

Waning trade winds curb low-oxygen region in the Pacific Ocean

8:00am, August 11, 2014
a sediment core

SUFFOCATING SEA  A timeline preserved in the layers of sediment cores (one shown) reveals that the oxygen-deprived North Pacific dead zone shrank during much of the 20th century warming period.

Waning winds could give the world’s largest oxygen-starved ocean region a breath of fresh air as the planet warms, researchers report in the Aug. 8 Science. Scientists previously thought the North Pacific dead zone would grow, not shrink, under climate change.

Dead zones naturally form at depths of about 200 to 1,000 meters, where sinking organic matter from the surface nourishes oxygen-gobbling bacteria. Because warm water can hold less dissolved oxygen than cold water, scientists have suggested that low-oxygen regions would expand as the climate warms. Earth scientist Curtis Deutsch of the University of Washington in Seattle and colleagues now show that the North Pacific dead zone shrank during much of the 20th century despite rising temperatures.

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