Pobeda Ice Island
Pobeda Ice Island, original Russian name остров Победы (остров = Island, Победа = Victory, meaning Pobeda Island or Victory Island), is an ice island in the Mawson Sea. It is located 160 km (99 mi) off the coast of Queen Mary Land, East Antarctica. This island, which exists periodically, is formed by the running aground of a tabular iceberg.
Periodic formation
The ice island is created and vanishes periodically. It is created by the calving of an enormous block of ice from Denman Glacier, located in the eastern part of Shackleton Ice Shelf. The resulting tabular iceberg drifts northwest until it runs aground upon a shoal north of the ice shelf. The iceberg remains locked in this position there for a decade or more, until has remodeled enough to free itself from the shoal. It then drifts into the open ocean, where it breaks into fragments. These iceberg fragments eventually melt as they drift into warmer waters. The floating tongue of the Denman Glacier, fed by ice from the interior of Antarctica, advances until a new large berg is calved about every 40 to 50 years.
Data
Pobeda Ice Island is variable in its dimensions, but is commonly up to 70 km (43 mi) long and 36 km (22 mi) wide, with an area of 1,500 km2 (579 sq mi).
The term "island" is technically incorrect, since this geographic feature is in reality a tabular iceberg with nearly vertical sides and a flat top.
Laws of physics dictate that 11% of an iceberg will extend above the water level (in salt water), while the remainder will be submerged. In the case of Pobeda Ice Island, whose flat surface is roughly 27 meters (89 ft) above sea level, this means that the iceberg extends to a depth of roughly 216 meters (709 ft) below sea level, and its total height is approximately 243 meters (797 ft). The further implication is that the ocean floor is also roughly 216 meters (709 ft) below sea level, at the point of the shoal.
History
At this position, an ice island was first sighted by the United States Exploring Expedition, led by Charles Wilkes, in February 1840. It prevented his westward passage around the Antarctic coast, and he named it Termination Land.
Douglas Mawson renamed the island Termination Ice Tongue when he encountered it on the 1911-13 Australasian Antarctic Expedition. No island was noted however at that location, when he returned during his 1929-31 BANZARE expedition.
A Soviet Expedition came across the island in 1960 and renamed it again, this time as Pobeda Ice Island, named for Soviet victory over the Axis powers in the Great Patriotic War. They even established a temporary research station on the island. Pobeda disappeared sometime in the 1970s, to be replaced by a new berg that calved in 1985. That one also disappeared in 2003 or 2004. There is currently no ice island at this location.
Pobeda Canyon
About 200 km (120 mi) north of Pobeda Ice Island lies Pobeda Canyon, an oceanic trench so named in 1956 by A. P. Lizitsin . It is located between 62°30′S 100°15′E and 64°30′S 097°35′E.
See also
- List of Antarctic islands south of 60° S
- Thwaites Iceberg Tongue
External links
Literature
- Bernard Stonehouse: Encyclopedia of Antarctica and the Southern Oceans. Wiley, Chichester/Hoboken 2002, ISBN 0-471-98665-8, S. 200