A23a iceberg moving north again after being trapped in vortex

The world's biggest iceberg is on the move again after being trapped in a vortex for most of the year.A23a is 3,800 sq km (1,500 sq miles), which is more than twice the size of Greater London, and is 400m (1,312ft) thick. It broke free of Antarctica in 1986 though soon became stuck just off the coast.The depth of the iceberg meant its bottom became lodged on the floor of the Weddell Sea, part of the Southern…