The major global deep ocean current has slowed by about 30 % since the 1990s due to melting Antarctic ice, which could have critical consequences for Earth's climate patterns and sea levels, new research suggests. The global circulation system, known as the Southern Ocean overturning circulation, plays a key role in influencing Earth's climate, including precipitation and warming patterns. It also determines how much heat and carbon dioxide the oceans store. Scientists warn that its slowdown could have drastic effects, including rising sea levels, changing weather patterns and depriving marine ecosystems of vital nutrients. "Changes in the overturning circulation are a big deal," said study co-author Dr Steve Rintoul, an oceanographer and Southern Ocean expert at the Australian government's Commonwealth Scientific and Industrial Research Organization (CSIRO).. (Donna Lu)