Perhaps the single most distinguishing feature of the Antarctic region is the ice. Ice seems to be an ever-present part of any landscape in this part of the world.
Indeed, the continent of Antarctica actually is buried, for the most part, under tons and tons of ice and only the tops of some of the taller mountains break through and appear above the surface of this protective envelope of frozen water.
Ice in the Antarctic comes in a variety of shapes and sizes. Ice forms at sea and for much of the year, the southern half of the Southern Ocean develops a skin of Sea Ice, which surrounds the continent and the southernmost islands. This formation may consist of what is known as Fast Ice, which grows out from the land to form continuous sheets over the water, or Pack Ice, which is largely made up of floes, the broken remains of larger ice sheets.
Sea ice begins to form in March when the autumn temperatures begin to fall. The ocean swell will often break apart the developing sheets but the cold air enables the ice sheets to continue to grow larger and larger. By August or September, in the height of winter, the Antarctic Peninsula and the rest of the continent are surrounded completely by sheets of fast ice ringed with wide bands of pack ice. This ice is often over 3 feet thick and at the height of winter extends many miles from shore, covering about 8 million square miles of ocean.
The sea ice rarely remains smooth and unbroken. Sometimes, the ice consolidates into irregular discs that resemble pancakes. This ice is sometimes called Pancake Ice.
The sea ice, although appearing to be a solid mass attached to the land, actually is often on the move. Wind and water currents help to drive large sections of ice against each other. This action also contributes to the rough-hewn appearance of the ice. Sometimes, the wind, waves and currents open sections of the ice as various floes are driven chaotically through the ocean. These sections of open water are known as polynyas, which are often used by ships for safe passage along the coast of the continent.
Huge blocks of ice afloat in the sea are known as Icebergs. These formations, some of the most beautiful in the world, have their origin in the cliffs of Antarctica’s ice coastline. Some of these bergs are so large, they are referred to as Ice Islands. These can measure several hundred miles in length and present significant hazards to navigation. Indeed, some of these are as big as some of the smaller states in the United States.
Some icebergs are flat-topped and square-cut. These are known as Tabular Icebergs. Other icebergs are more irregular in shape and size. These are often called Growlers, Bergy Bits and Brash Ice.
All icebergs disintegrate over time as they float through the (relatively) warmer water. Of course, the largest icebergs can exist for many years.
Icebergs are generally colored white, blue or green. White color generally indicates the presence of air trapped in the ice while blue and green indicates solid, hard packed ice.
Between one-quarter and one-seventh of an iceberg’s mass appears above the surface, depending upon the age of the iceberg and the amount of air trapped in the ice. The rest is below the water and this is the part of the iceberg that is most dangerous to passing ships.
Wind, waves and currents constantly sculpt icebergs. In warmer summer weather, fresh water can sometimes be seen running off the flanks these objects. Sometimes, due to the corrosive action of the elements, icebergs will roll, revealing smooth sections previously sheltered by water.
One of the most famous formations of ice on the planet is the Ross Ice Shelf. Covering 322,400 square miles (the size of France) the Ross Ice Shelf was discovered in 1841 by James Clark Ross. The mean thickness of the ice here is between 1098 and 2296 feet but in some areas it is greater than 3000 feet thick! Because of its immense bulk, it is hard for people to believe that the entire shelf is actually floating! It moves as fast as 3000 feet per year and an estimated 100 cubic miles of icebergs calve from the shelf each year. The entire ice shelf contains about 14,260 cubic miles of ice. In 1911, Roald Amundson, upon seeing the Ross Ice Shelf, was moved to write:
"At 2:30pm we came in sight of the Great Ice Barrier [ Ross Ice Shelf ]. Slowly, it rose up out of the sea until we were face to face with it in all its imposing majesty. It is difficult with the help of pen to give and idea of the impression this mighty wall of ice makes on the observer who is confronted with it for the first time. It is altogether a thing which can hardly be described."
And so is Antarctica itself.
Submerged ice which is attached to the sea bottom.
A piece of floating ice rising between 1 to 5 meters above the water.
The remains of large pieces of ice crashing into each other and forming a large heaping pile.
Sea ice attached to the shore or between grounded ice bergs.
Needle-shaped ice crystals that form a icy slush in the water.
The stage at which the water gets a matte looking appearance when its between freezing and frazil ice.
An area where ice floes have rafted or piled up on top of each other, often reaching heights several yards.
A lighter section underneath the clouds which indicates reflecting light off the ice below. This technique was used by many early explorers to help steer them away from ice packs.
The short summer season when the fast ice has broken away to allow ships to come close to the Antarctic coastline.
A section of open water within pack ice and large ice floes.
Thin crust of floating ice that bends in the waves, but does not break. The darker in appearance, the thinner the nilas is.
Discs of young ice, formed when waves jostle them against each other rounding their edges.
A crack between sea ice and the shoreline. This crack is caused by the rise and fall of the tide and is usually to wide to cross safely.
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