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Ross Ice Shelf

Ross Ice Shelf

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The Ross Ice Shelf is the largest ice shelf
Ice shelf
An ice shelf is a thick, floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Ice shelves are only found in Antarctica, Greenland and Canada. The boundary between the floating ice shelf and the grounded ice that feeds it is called...

 of Antarctica (an area of roughly 487 000 km2, and about 800 km across: about the size of France). It is several hundred metres thick. The nearly vertical ice front to the open sea is more than 600 km long, and between 15 and 50 metres high above the water surface. 90 percent of the floating ice, however, is below the water surface.

Most of Ross Ice Shelf is located within the Ross Dependency
Ross Dependency
The Ross Dependency is a region of Antarctica defined by a sector originating at the South Pole, passing along longitudes 160° east to 150° west, and terminating at latitude 60° south...

 claimed by New Zealand.

The ice shelf was named after Captain Sir James Clark Ross
James Clark Ross
Sir James Clark Ross , was a British naval officer and explorer. He explored the Arctic with his uncle Sir John Ross and Sir William Parry, and later led his own expedition to Antarctica.-Arctic explorer:...

 who discovered it on 28 January 1841. It was originally named the Victoria barrier by Ross, after Queen Victoria and later the Great Ice Barrier as it prevented sailing further south. Ross mapped the ice front eastward to 160°W.

Exploration



On January 5, 1841, a British Admiralty team in the Erebus
HMS Erebus (1826)
HMS Erebus was a Hecla-class bomb vessel designed by Sir Henry Peake and constructed by the Royal Navy in Pembroke dockyard, Wales in 1826. The vessel was named after the dark region in Hades of Greek mythology called Erebus...

and the Terror
HMS Terror (1813)
HMS Terror was a bomb vessel designed by Sir Henry Peake and constructed by the Royal Navy in the Davy shipyard in Topsham, Devon. The ship, variously listed as being of either 326 or 340 tons, carried two mortars, one and one .-War service:...

, three-masted
Mast (sailing)
The mast of a sailing vessel is a tall, vertical, or near vertical, spar, or arrangement of spars, which supports the sails. Large ships have several masts, with the size and configuration depending on the style of ship...

 ships with specially strengthened wooden hulls
Hull (watercraft)
A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...

, was going through the pack ice of the Pacific near Antarctica in an attempt to determine the position of the South Magnetic Pole. Four days later, they found their way into open water and were hoping that they would have a clear passage to their destination; but on 11 January, the men were faced with an enormous mass of ice.

Sir James Clark Ross
James Clark Ross
Sir James Clark Ross , was a British naval officer and explorer. He explored the Arctic with his uncle Sir John Ross and Sir William Parry, and later led his own expedition to Antarctica.-Arctic explorer:...

, who was the expedition's commander, remarked: '"Well, there's no more chance of sailing through that than through the cliffs of Dover".' Ross, who in 1831 had located the North Magnetic Pole
North Magnetic Pole
The Earth's North Magnetic Pole is the point on the surface of the Northern Hemisphere at which the Earth's magnetic field points vertically downwards . Though geographically in the north, it is, by the direction of the magnetic field lines, physically the south pole of the Earth's magnetic field...

, spent the next two years vainly searching for a sea passage to the South Pole; later, his name was given to the ice shelf and the sea surrounding it. Two volcanoes in the region were named by Ross for his vessels.

For early Antarctic explorers seeking to reach the South Pole, the Ross Ice Shelf became a starting area. In a first exploration of the area, Robert Falcon Scott
Robert Falcon Scott
Captain Robert Falcon Scott, CVO was a Royal Navy officer and explorer who led two expeditions to the Antarctic regions: the Discovery Expedition, 1901–04, and the ill-fated Terra Nova Expedition, 1910–13...

 made a significant study of the shelf and its surroundings from his expedition's base on Ross Island
Ross Island
Ross Island is an island formed by four volcanoes in the Ross Sea near the continent of Antarctica, off the coast of Victoria Land in McMurdo Sound.-Geography:...

. These findings were presented at a lecture entitled "Universitas Antarctica!" given 7 June 1911, and were published in the account of Scott's expedition.


Both Roald Amundsen
Roald Amundsen
Roald Engelbregt Gravning Amundsen was a Norwegian explorer of polar regions. He led the first Antarctic expedition to reach the South Pole between 1910 and 1912 and he was the first person to reach both the North and South Poles. He is also known as the first to traverse the Northwest Passage....

 and Scott crossed the shelf to reach the Pole in 1911. Amundsen wrote that, "Along its outer edge the Barrier shows an even, flat surface; but here, inside the bay, the conditions were entirely different. Even from the deck of the Fram
Fram
Fram is a ship that was used in expeditions of the Arctic and Antarctic regions by the Norwegian explorers Fridtjof Nansen, Otto Sverdrup, Oscar Wisting, and Roald Amundsen between 1893 and 1912...

we were able to observe great disturbances of the surface in every direction; huge ridges with hollows between them extended on all sides. The greatest elevation lay to the south in the form of a lofty, arched ridge, which we took to be about 500 feet high on the horizon. But it might be assumed that this ridge continued to rise beyond the range of vision."

The next day, the party made its first steps on the Barrier. "After half an hour’s march we were already at the first important point — the connection between the sea-ice and the Barrier. This connection had always haunted our brains. What would it be like? A high, perpendicular face of ice, up which we should have to haul our things laboriously with the help of tackles? Or a great and dangerous fissure, which we should not be able to cross without going a long way round? We naturally expected something of the sort. This mighty and terrible monster would, of course, offer resistance in some form or other," he wrote.

"The mystic Barrier! All accounts without exception, from the days of Ross to the present time, had spoken of this remarkable natural formation with apprehensive awe. It was as though one could always read between the lines the same sentence: 'Hush, be quiet! the mystic Barrier !'

"One, two, three, and a little jump, and the Barrier was surmounted!"

Composition and movement



Ice shelves are thick plates of ice, formed continuously by glaciers, that float atop an ocean. The presence of the shelves acts as "brakes" for the glaciers. These shelves serve another important purpose -- "they moderate the amount of melting that occurs on the glaciers' surfaces. Once their ice shelves are removed, the glaciers increase in speed due to meltwater percolation and/or a reduction of braking forces, and they may begin to dump more ice into the ocean than they gather as snow in their catchments. Glacier ice speed increases are already observed in Peninsula areas where ice shelves disintegrated in prior years."
The Ross Ice Shelf is one of many such shelves. It is about the size of France, and reaches into Antarctica from the south. The ice mass is about 800 km (497.1 mi) wide and 970km (600 miles) long. In some places, namely its southern areas, the ice shelf can be almost 750 m (2,450 ft) thick. The Ross Ice Shelf pushes out into the sea at the rate of between 1.5 m (5ft) and 3 m (10 ft) a day. There are other glaciers that gradually add bulk to it. At the same time, the freezing
Freezing
Freezing or solidification is a phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. The reverse process is melting....

 of seawater below the ice mass increases the thickness of the ice from 40 cm (16 in) to 50 cm (20 in). Sometimes, fissures and cracks may cause part of the shelf to break off; the largest known is about 31000 km² (11,969.2 sq mi), that is slightly larger than the size of Belgium. Iceberg B-15
Iceberg B-15
Iceberg B-15 is one of the world's largest recorded icebergs. It measured around 295 km long and 37 km wide , with a surface area of 11,000 km² larger than the island of Jamaica. The mass was estimated around three billion tonnes...

, the world's largest recorded iceberg
Iceberg
An iceberg is a large piece of ice from freshwater that has broken off from a snow-formed glacier or ice shelf and is floating in open water. It may subsequently become frozen into pack ice...

, was calved from the Ross Ice Shelf during March 2000.

Scientists have long been intrigued by the shelf and its composition.
In fact, most of the scientific teams have made camps on or adjacent to the Ross Ice Shelf. This includes McMurdo Station
McMurdo Station
McMurdo Station is a U.S. Antarctic research center located on the southern tip of Ross Island, which is in the New Zealand-claimed Ross Dependency on the shore of McMurdo Sound in Antarctica. It is operated by the United States through the United States Antarctic Program, a branch of the National...

. One major effort was a series of studies conducted in 1957 and 1958, which were continued during the 1960-61 season. The efforts involved an international team of scientists. Some parties explored the glaciers and others the valleys on the ice shelf.

From 1967 to 1972 the Scott Polar Research Institute
Scott Polar Research Institute
The Scott Polar Research Institute is a centre for research into the polar regions and glaciology worldwide. It is a sub-department of the Department of Geography in the University of Cambridge, located on Lensfield Road in the south of Cambridge ....

 reported extensive observations using radio echo sounding. The technique allowed measurements to be taken from the air; allowing a criss cross track of 35,000 km to be covered; compared with a 3,000 km track from previous seismic sounding on the ground. More detailed surveys were executed between 1973 and 1978.

A significant scientific endeavor called the Ross Ice Shelf Project was launched with a plan of drilling into the shelf to sample the biomass in the area and make other determinations about the shelf and its relationship to the sea floor. The Project included surface glaciological observations as well as drilling, and the glaciological portion started during the planning phase of the drilling. The drilling portion of the project was to have begun during 1974, but the actual drilling was delayed until 1976. Finally, in 1977, the scientists were able to drill successfully through the ice, making a hole that could be sampled every few days for three weeks. The team was able to map the sea floor, study the tides, and assess the fish and various other forms of life in the waters. The team also examined the oceanographic and geological conditions as well as the temperature of the ice. They estimated that the base of the shelf was -2.16° Celsius (27.3°F). They also made other calculations about the fluctuations of the temperatures.

The results of these various projects are published in a series of reports in Science magazine, published 2 February 1979.

During the 1980s, a network of weather stations were installed to record temperatures on the shelf as well as throughout the more remote parts of the continent.


University of Colorado's National Snow and Ice Data Center
National Snow and Ice Data Center
The National Snow and Ice Data Center, or NSIDC, is a United States information and referral center in support of polar and cryospheric research...

 has been studying ice shelves and, in 2002, announced that, based on several break ups of ice shelves, including Larsen B, has begun to reassess their stability. Their scientists stated that the temperature of the warmest portion of the shelf is "only a few degrees too cool in summer presently to undergo the same kind of retreat process. The Ross Ice Shelf is the main outlet for several major glaciers draining the West Antarctic Ice Sheet
West Antarctic Ice Sheet
The West Antarctic Ice Sheet is the segment of the continental ice sheet that covers West Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains which lies in the Western Hemisphere. The WAIS is classified as a marine-based ice sheet, meaning that its bed lies well...

, which contains the equivalent of 5 m of sea level rise in its above-sea-level ice." The report added that observations of "iceberg calving
Ice calving
Ice calving, also known as glacier calving or iceberg calving, is a form of ice ablation or ice disruption. It is the sudden release and breaking away of a mass of ice from a glacier, iceberg, ice front, ice shelf, or crevasse...

" on the Ross Ice Shelf are, in their opinion, unrelated to its stability.

Continuing scientific exploration continues to uncover interesting information and the analyses have resulted in some interesting theories being posited and publicized. One such opinion, given in 2006 based on a geological survey, suggested that the ice shelf had collapsed previously, perhaps suddenly, which could well happen again.

See also

  • Iceberg B-17B
    Iceberg B-17B
    Iceberg B-17B is an iceberg twice the size of Manhattan, floating in the southern ocean approximately off the coast of Western Australia. Iceberg B-17B measures approximately and calved off the Ross Ice Shelf in 1999....

  • List of Antarctic ice shelves
  • Nimrod Expedition
    Nimrod Expedition
    The British Antarctic Expedition 1907–09, otherwise known as the Nimrod Expedition, was the first of three expeditions to the Antarctic led by Ernest Shackleton. Its main target, among a range of geographical and scientific objectives, was to be first to the South Pole...

  • Ross Gyre
    Ross Gyre
    The Ross Gyre is one of the two gyres that exist within the Southern Ocean. The gyre is located in the Ross Sea, and rotates clockwise. The gyre is formed by interactions between the Antarctic Circumpolar Current and the Antarctic Continental Shelf...


External links