Ice

The Ice Cap

The ice cap or inland ice covers 1,833,900 square km, equivalent to 85 percent of Greenland's total area, and extends 2,500 km (1,553 miles) from north to south and up to 1,000 km from east to west. At its center, the ice can be up to 3 km thick, representing 10 percent of the world's total fresh water reserves. If all the ice were to melt, the world's oceans would rise seven meters. Ice caps and glaciers are not completely "frozen" but flow and move as snow accumulates above and eventually melts far below. Icebergs snap off the glaciers at the edges of the ice cap, it spreads under its own weight into periglacial flows and frozen rivers that pour out from the margins.

Glaciers

Activities on glaciers should be lead by an experienced person. Most glaciers are relatively easy to travel with adequate glacier gear. Crevasses are usually recognizable and negotiable. The most important part lies in the decision making of the leader, in recognizing potential danger zones and making decisions in the case of foul weather and low visibility.

Icebergs

The juggernauts of the Arctic. Glacial ice forms out of compacted snow, so icebergs are made entirely of fresh water. As snow is squeezed under its own weight on the upper reaches of the glaciers, it begins to flow downhill to the sea. Tongues of ice flow out onto the surface of the water. Gradually, wind and waves weaken the tongue of the glacier until it gives way. Great blocks of glacier break off in a process called "calving," and begin to drift southward in the current. Typically, one-fifth to one-seventh of an iceberg protrudes above the water. The submerged core is made of rock-hard, freshwater ice. The average age of that ice is thought to be about 15,000 years. But some may date back to the last ice age. In their glory, icebergs can tower hundreds of feet above the water. In the summer, the iceberg armadas begin to crumble. Weakened by the sun, they sometimes collapse in a great, splashing mess, leaving a litter of "bergy bits" and "growlers."

Sea Ice

- also called pack ice, is a whole other beast. It forms from frozen seawater, as its name suggests, not compacted snow. Sea ice is dynamic: Like a plant or animal, it grows in stages, with different names for different stages. It changes with the seasons. And it is almost always on the move, impelled by currents and winds. Sea ice forms when the temperature of the ocean surface falls below -1,89 Celsius. Unlike the calm surface of a lake, where ice forms in a gradually thickening sheet, the ocean surface is frequently stirred by waves. This leads to some interesting forms of ice. In turbulent water, tiny disc-shaped crystals of ice form into a substance called frazil. As they are stirred through the sea surface, the crystals give the water a greasy appearance, hence the name "grease ice." Another form that sea ice takes as it grows is shuga, composed of small chunks of ice that undulate on the surface of the water in a sheet. When the ice clumps together, it forms rounded sheets with upturned edges, called pancake ice. The pancakes damp down the waves somewhat, allowing pancakes to consolidate into larger pancakes. Eventually, the pancake ice freezes into floes, larger sheets of sea ice floating on the water's surface. There are two types of pack ice: first-year ice and multi-year ice. First-year ice freezes in fall or early winter and melts in the summer. Typically, first-year ice is between a foot to six feet thick. Multi-year ice is simply pack ice that has survived at least one winter. A smaller fraction of the polar sea ice grows along shorelines and in enclosed bodies of water such as bays. This is called lastfast ice. Sea ice is dynamic in another sense: It is alive. Far from being a frozen wasteland, floating pack ice is laced with creatures living in a complex food web.

Icebergs and glacier fronts

The shifting or cracking of an iceberg, or the calving of a glacier front can cause large waves on shore. Camps should be set up well in consideration of such hazards and equipment should be carried up to a safe height. An iceberg can topple over at any time and it is dangerous for kayakers to paddle too close.

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