Antarctica's big crack revealed
In a scene straight out of a science-fiction disaster movie, space agency Nasa has revealed what a vast crack across Antarctica looks like up close.
The 2004 movie The Day After Tomorrow opened with a the Antarctic iceshelf cracking ahead of global extreme weather, and now Nasa has it live and on YouTube.
In October 2011, researchers flying in NASA's Operation IceBridge campaign made the first-ever detailed, airborne measurements of a major iceberg calving event while it was in progress.
By February IceBridge's team had mapped the crack in Antarctica's Pine Island Glacier in a way that allowed glaciologists to fly through the icy canyon.
The animation was created by draping aerial photographs from the Digital Mapping System - a still camera with very precise geolocation ability - over data from the Airborne Topographic Mapper - a scanning laser altimeter that measures changes in the surface elevation of the ice.
Both instruments were flown on NASA's DC-8 research airplane, and the data was collected on October 26, 2011.
The crack formed in the ice shelf that extended from one of West Antarctica's fastest-moving glaciers.
The path of the crack in the animation stretched roughly 30 kilometres in length (the actual crack was much longer), with an average width of about 80 metres. It was 250 metres at its widest.
The canyon ranged from 50 to 60 metres deep, with the floor being roughly at the water line of the Amundsen Sea.
Radar measurements suggested the ice shelf was about half a kilometre thick, with only a third of it above water.
Nasa said scientists had been waiting for the crack to propagate through the rest of the ice shelf and release an iceberg, which they estimated could span 900 square kilometres.
If it did not split off soon, however, the sea ice that formed with the onset of southern winter might keep the ice chunk trapped against the coast for a while.