Magazine article Science News

Dead Zone Shrank as Winds Declined: Warming May Not Enlarge North Pacific Low-Oxygen Region

Magazine article Science News

Dead Zone Shrank as Winds Declined: Warming May Not Enlarge North Pacific Low-Oxygen Region

Article excerpt

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.

Curtis Deutsch of the University of Washington in Seattle and colleagues show that the North Pacific dead zone shrank during much of the 20th century despite rising temperatures. "Our results totally go against the paradigm that a warming climate causes low-oxygen regions to expand," Deutsch says.

Dead zones naturally form at depths of about 200 to 1,000 meters, where sinking organic matter from the surface nourishes oxygen-gobbling bacteria. Warm water holds less dissolved oxygen than cold water, so researchers thought that dead zones would grow as the climate warmed.

The North Pacific dead zone stretches westward from North and Central America, encompassing an area larger than Canada. Most marine life cannot survive there and either vacates or suffocates.

The zone is driven by the Pacific trade winds, which draw up nutrients from the deep sea that fertilize plankton near the surface. As the plankton die, dead organic matter descends, feeding bacteria that consume what little oxygen remains in the water. The microbes deposit large amounts of a heavy form of nitrogen onto the seafloor.

To reconstruct the zone's past, Deutsch's colleagues collected sediment cores at three sites under the North Pacific dead zone. Each millimeter-thick layer of accrued sediment corresponds roughly to a year in time. By precisely measuring the amount of heavy nitrogen in each layer, the researchers tracked oxygen increases and thereby inferred decreases in the zone's size over the last 150 years. …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.