The new study used ocean temperature measurements from a global array of 3,500 Argo floats and other ocean sensors, and the researchers say this shifting pattern of ocean heat accounts for the slowdown in the global surface temperature trend observed during the past decade.
Veronica Nieves, Josh Willis and Bill Patzert of NASA’s Jet Propulsion Laboratory (JPL), Pasadena, California, found a specific layer of the Indian and Pacific oceans between 300 and 1,000 feet (100 and 300 meters) below the surface has been accumulating more heat than previously recognized. They also found the movement of warm water has affected surface temperatures.
Willis said that Greenhouse gases continued to trap extra heat, but for about 10 years starting in the early 2000s, global average surface temperature stopped climbing, and even cooled a bit.
In the study, researchers analysed 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.
Nieves, the lead author of the study, said that the western Pacific got so warm that some of the warm water had been leaking into the Indian Ocean through the Indonesian archipelago. Given the fact the Pacific Decadal Oscillation seems to be shifting to a warm phase, ocean heating in the Pacific will definitely drive a major surge in global surface warming.
In the long term, there was robust evidence of unabated global warming, she added.
The study is published Thursday in the journal Science.