From: UCLA Newsroom
Published July 17, 2015 09:16 AM

Oceans slowed global temperature rise

A new study of ocean temperature measurements shows that in recent years, extra heat from greenhouse gases has been trapped in the subsurface waters of the Pacific and Indian oceans, thus accounting for the slowdown in the global surface temperature increase observed during the past decade, researchers say.

A specific layer of the Indian and Pacific oceans between 300 and 1,000 feet below the surface has been accumulating more heat than previously recognized, according to climate researchers from UCLA and NASA’s Jet Propulsion Laboratory. They also found the movement of warm water has affected surface temperatures. The results were published July 9 in the journal Science.

During the 20th century, as greenhouse gas concentrations increased and trapped more heat on Earth, global surface temperatures also increased. However, starting in the early 2000s though greenhouse gases continued to trap extra heat, the global average surface temperature stopped climbing for about a decade and even cooled a bit.

In the study, researchers analyzed direct ocean temperature measurements, including observations from a global network of about 3,500 ocean temperature probes known as the Argo array. These measurements show temperatures below the surface have been increasing.

The Pacific Ocean is the primary source of the subsurface warm water found in the study, though some of that water now has been pushed to the Indian Ocean. Since 2003, unusually strong trade winds and other climatic features have been piling up warm water in the upper 1,000 feet of the western Pacific, pinning it against Asia and Australia.

“The western Pacific got so warm that some of the warm water is leaking into the Indian Ocean through the Indonesian archipelago,” said Veronica Nieves, lead author of the study and a UCLA researcher with the UCLA Joint Institute for Regional Earth System Science and Engineering, a scientific collaboration between UCLA and NASA’s Jet Propulsion Laboratory.

The movement of the warm Pacific water westward pulled heat away from the surface waters of the central and eastern Pacific, which resulted in unusually cool surface temperatures during the last decade. Because the air temperature over the ocean is closely related to the ocean temperature, this provides a plausible explanation for the global cooling trend in surface temperature, Nieves said.

Continue reading at UCLA Newsroom.

Ocean image via Shutterstock.

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