Icebergs

          Every year thousand of icebergs leave Antarctica to melt in northern waters. No one knows exactly how much ice leaves Antarctica every year, but on a soviet survey in 1965 were 30000 icebergs counted in a area of 4000km² between longitude 44°E and 168°E. All these icebergs had an approximately volume of 4165km³. The icebergs are not formed by freezing of the sea, but come from the outward flow of the continental ice sheet. Some are formed by the collapse of ice cliffs or a glacier tongue flowing directly into the sea. About 80% are calved from the ice shelves into which major glaciers flow. These icebergs are also the largest, like the monster chunk of the Ross Ice Shelf covering 31’000km² which broke off in 1956.

Iceberg voyages

          Once released, icebergs are carried northward and westward at up to 8 km a day in the easterly wind and currents around the continent until they reach the Antarctic Convergence. There they meet warmer water and they rapidly melt. The furthest north and iceberg has been sighted was at 26°30’S in the South Atlantic, almost in the tropics.

          Most icebergs take several seasons over his process, and some are grounded for years in shallow bays where they become part of the local scenery. Overall, about 2 million tonnes of the Antarctic ice sheet is calved of each year in icebergs. This is equivalent to nearly half the world’s drinking water. It has been suggested that icebergs could be towed to dry countries like Australia and melted to supply water, but the technical problems are enormous.

Ice shelves

Sea ice