SINGAPORE: The breaking off of a Luxembourg-sized iceberg in Antarctica could affect ocean circulation patterns and be a harbinger of changes to come from global warming, scientists on a mission to the frozen continent say. Last February, a 2,500 sq-km iceberg broke off from a giant floating tongue of ice from the Mertz Glacier after being rammed by an even larger iceberg. The ice tongue, sticking out into the Southern Ocean, had acted like a dam, preventing sea ice from moving into a permanently open section of water to the west. But now with the ice tongue gone due to the collision, scientists fear it could trigger changes to the behavior of a major part of global ocean circulation patterns that shift heat around the globe via myriad currents at the surface and along the bottom. The area around the glacier tongue, since halved in length by the collision, and to the west are one of the few places around Antarctica where dense, salty water is formed and sinks to the depths of the ocean, said mission leader Steve Rintoul Monday. This dense bottom water as it is called, is a key driver of the global overturning circulation that includes the current that brings warm Atlantic waters to western Europe. But he said there was a risk the area could now be less effective in producing the bottom water that feeds the deep ocean currents, which influence global climate patterns. “This is one of the few places around Antarctica where the sea surface is made dense enough to sink to the deep ocean,” Rintoul told Reuters from the icebreaker Aurora Australis near the glacier about 2,500km south of Hobart, capital of Australia's Tasmania state. “If the area is less effective in forming less dense water, then that salinity now should be lower than it was in the past.” Rintoul is leading an international team of nearly 40 scientists on a voyage studying the impacts of the loss of the glacier tongue as well as changes to ocean temperatures, salinity and acidity. Oceans act as a brake on climate change by soaking up large amounts of heat and carbon dioxide, the main greenhouse gas, from the atmosphere. But the more CO2 the oceans take up, the more acidic they become, making it harder for animals such as sea snails to make their shells.
