Giant icebergs head to watery end at island graveyard

Jonathan Amos in the BBC: The huge tabular blocks of ice that frequently break off Antarctica get swept towards the Atlantic and then ground on the shallow continental shelf that surrounds the 170km-long island. As they crumble and melt, they dump billions of tonnes of freshwater into the local marine environment.

UK scientists say the giants have quite dramatic impacts, even altering the food webs for South Georgia's animals. … "The scale of some these icebergs is something else," said oceanographer Dr Mark Brandon from the Open University.

"The iceberg known as A-38 had a mass of 300 gigatonnes. It broke up into two fragments, but it also shattered into lots of smaller bergs. Each smaller berg was still fairly big and each dumped lots of freshwater into the system."

…With a group of colleagues he planted scientific moorings off South Georgia in several hundred metres of water. The moorings held sensors to monitor the physical properties of the water, including temperature, salinity and water velocity. The presence of plankton was also measured. The moorings were in prime position to capture what happened when the mega-berg A-38 turned up in 2004.

It is one of many tabular blocks, such as B-10A and A-22B, which have been caught at South Georgia, which lies downstream of the Antarctic Peninsula in currents known as the Weddell-Scotia Confluence…

From NASA, the split of the A38-B iceberg is recorded in this series of images. The iceberg was originally part of the massive A-38 iceberg, which broke from the Ronne Ice Shelf in Antarctica. Another section of the A-38 iceberg, A-39D, was covered in melt water ponds as it drifted past South Georgia Island in late January 2004—the height of the summer in the Southern Hemisphere.