Saturday, November 5, 2011
iceberg in antarctica
A rift has formed in the shelf of floating ice in front of the Pine Island Glacier (PIG). The surface crack in the PIG runs for almost 30km (20 miles), is 60m (200ft) deep and is growing every day. US space agency (Nasa) researchers expect the eventual iceberg to cover about 880 sq km - an area the size of Berlin. It should break away towards the end of the year or early in 2012. Pine Island Glacier is one of the largest and fastest-moving tongues of ice on the White Continent and drains something like 10% of all the ice flowing out of the West Antarctic Ice Sheet into the ocean. In recent years, satellite and airborne measurements have recorded a marked thinning of the PIG, which may be related to climate changes. The biggest icebergs can have a major impact on their surroundings.
As they crumble and melt, they dump millions of tonnes of freshwater into the local marine environment. Dust and rock fragments picked up on land act as nutrients when they fall into the ocean, fuelling life such as algae and diatoms right at the bottom of food webs. But these huge tabular blocks can also put obstacles in the way of animals trying to get to familiar feeding grounds.