It stands to reason that as the atmosphere warms from the buildup of greenhouse gases, so does the ocean. Scientists have long suspected this was true, but they did not have enough solid evidence. Now they do. Data compiled by Marinexplore in Sunnyvale, Calif., not only confirm previous studies that the world's oceans are simmering, but they also bring surprising news: the heating extends beyond the first few meters of surface waters, down to 700 meters. Because most organisms live in the top 400 meters, the data suggest that warming could affect most marine life, altering food chains and migrations. It could change the distribution of life—from tiny phytoplankton to big whales—across the seven seas. “The more the atmosphere warms up, the more heat it transfers to the ocean,” says Roberto De Almeida, an ocean data engineer at Marinexplore. “That heat propagates downward.” Indeed, the extra energy could affect massive ocean currents and the weather patterns they influence.

Credit: Jen Christiansen

SCIENTIFIC AMERICAN ONLINE

See a map of ocean temperature change at ScientificAmerican.com/apr2013/graphic-science