Earth's complete water cycle is very dynamic. The water cycle moves through its various states on or through Earth—gas, liquid, and solid— sometimes quickly, other times slowly. It moves most dynamically through the atmosphere as a gas (water vapor) and as a liquid through the atmosphere or on Earth as rain and in rivers. Water can transfer fairly rapidly through evaporation, condensation, clouds, and precipitation; but it can also be stored for extremely long periods of time in various reservoirs such as lakes, ponds, and catchment basins. It can be stored in its liquid state in the ocean or in deep aquifers under the ground; it can also be stored for even longer periods of time in its solid form, as snow or ice in ice caps, sheets, and shelves.
Even though the water cycle is dynamic—it is always in motion— more water is in storage at any given time than is actively moving through the system. Most of this long-term storage is in the form of ice. Nearly all of Earth's ice storage exists in two geographic locations: Antarctica and Greenland. These two locations have enormous ice caps because of the landmasses' extreme polar (high-latitude) locations. The presence of ice is also a factor of cold ocean currents, atmospheric circulation, temperature, and positive feedback mechanisms. For example, ice has a high albedo, causing most of the incoming solar radiation to be reflected back to space instead of absorbed and thereby ensuring that the ice does not melt. In fact, Antarctica contains almost 90 percent of this total, Greenland, nearly 10 percent. Of all Earth's water, the amount locked up as ice only accounts for approximately 1.7 percent. While this may not seem a significant amount, it is because it represents a huge percentage of the world's freshwater, that which is available as potential drinking water for humans. The reason why it is considered potential drinking water is because the water held in storage in ice does not contain salt, as ocean water does. According to the USGS, the water stored in ice represents around 68.7 percent of all the freshwater located on Earth. This makes the world's ice a very important natural resource. In addition, one of the largest impacts this stored ice has on the world's weather is its albedo. The high reflectance
South Georgia Island
Bouvet o Island (NORWAY)
PRINCE EDWARD °° ISLANDS (SOUTH AFRICA)
South Georgia Island
of the Sun's incoming energy affects both Earth's temperature and wind patterns.
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