The term 'cryosphere' is derived from Krios, which is a Greek word that means cold. It is the part of the Earth where water is in its solid form. It comprises snow, ice crystals, ice sheets, glaciers, icebergs, sea ice, frozen ground, etc. While water remains in its frozen state all-year-round at some places, the cryosphere is a seasonal feature in regions where ice or snow melts into water during summer. Glaciers and ice caps contain about three-fourth of the Earth's freshwater. It provides drinking water for more than a billion people around the world. The cryosphere is concentrated around the North and South Pole, but there are other places too in the world that form a part of this sphere. Water can be found in its solid or frozen form, as snow cover, glaciers, ice caps, ice sheets, sea ice, lake ice, river ice, and frozen ground. It is an integral part of the Earth system, which interacts with the hydrosphere, atmosphere, geosphere, and biosphere. Basically, the cryosphere includes different forms of frozen water. During winter, snow covers the ground at high latitudes. Most glaciers are located near the North and South Pole, or at high elevations. Ice sheets (large masses of glacial ice and snow that cover large areas of land) and glaciers move towards the land in polar regions. Permafrost refers to ground that is permanently frozen. Also, sea ice, icebergs, and ice shelves can be found in the polar regions. Snow is a form of precipitation that falls from the clouds. When the temperature falls below the freezing point (0ºC/32ºF), ice crystals or snowflakes (combination of ice crystals) form in the clouds. They form around the particles that are carried by the wind into the atmosphere. When they become larger and heavier, they fall on the Earth. Snowflakes can have a symmetrical hexagonal shape. When it comes to their shape, the temperature is a determining factor. Places at high altitudes or regions that have very low temperatures throughout the year are covered with snow always. In some places, the snow cover is seasonal, as the snow melts during the summer months. Due to the phenomenon of global warming, the extent of snow cover on some mountains is getting reduced. According to the Environmental Protection Agency, between 1972 and 2013, the average snow-covered portion of North America decreased at a rate of about 3,500 square miles per year. The formation of ice takes place when temperatures fall below the freezing point, causing water to turn into ice. Ice is involved in the formation of glaciers, sea ice, ice shelves, icebergs, frozen ground, etc. Both, snow and ice reflect sunlight, thereby affecting the temperature over the surface of the Earth. Changes in snow and ice cover can affect the energy balance. Glaciers are thick masses of ice that account for about 75% of freshwater. These form in places where there's a large amount of snowfall, and the temperatures are very low throughout the year. They form in areas where the annual snowfall exceeds the amount of snow that melts each year. Needless to say, glaciers are found in polar regions, and regions located at high altitudes. For glaciers to form, snow must continue to fall. As the snow keeps falling, the snow at the bottom gets compressed. The pressure from the overlying layers of snow turns it into ice. The pressure also squeezes out the tiny pockets of air between the ice crystals. This causes glacial ice to appear blue. It must be noted that glaciers are slow-moving masses of ice. Continental glaciers, which are also called ice sheets, cover a large area in the polar regions. Ice sheets are located in Greenland and Antarctica. At times, glacial ice moves downhill, sliding at the base, due to the enormous pressure of the ice on the bottom. While moving, glacial ice carves the surface of the Earth, thereby creating ridges, valleys, moraines, etc. Found in Antarctica, Greenland, and Canada, ice shelves are thick, floating slabs of ice, that form when a glacier or ice sheet reaches the coast. At the coast, the ice extends beyond the land, and floats when the depth of the floating ice is less than the depth of water, thereby forming a floating platform of ice on the water. The largest ice shelf is located in Antarctica, and is called Ross Ice Shelf. This ice shelf is approximately the size of France. At times, chunks of ice can break away from the edge of the glacier or ice sheet into the water. This process is referred to as calving. It is responsible for the formation of icebergs. Ice shelves help in confining a glacier or ice cap to the land. Concerns have been raised about the melting of ice shelves due to global warming. If these ice shelves break away into the ocean at the grounding line or the point where they connect to the land, the glacier would move towards the sea at a fast rate, thereby causing an increase in the sea level. As the name suggests, sea ice refers to frozen seawater. It should not be mistaken for an iceberg, as icebergs comprise freshwater, and are much thicker than sea ice, which is salty on account of being formed from sea water. In regions where the temperature is not low throughout the year, sea ice melts during the summer, and forms during the winter. This can be found in the polar regions. Sea ice is essential for polar bears and penguins. Due to global warming, the amount of sea ice in the Arctic ocean has been decreasing. Even the thickness of the ice has decreased. Scientists believe that there wouldn't be sea ice in the Arctic in the summer months by the end of the 21st century. It is believed that Adelie penguins are abandoning their nests in the northern part of the Antarctic Peninsula due to the lack of sea ice. This region is the warmest part of Antarctica, where sea ice is not even present during winter. The term 'permafrost' refers to frozen ground. It is found at high latitudes, like the Arctic and Antarctic. Since it is the ground (soil, rock) in which water has frozen, it is also considered to be a part of the geosphere. The thickness of the active layer or the top surface of this ground ranges from ½ to 4 meters. This layer thaws and refreezes with the seasons. If there's an active layer that thaws during anytime of the year, plants might survive, as their roots can permeate through this layer to get water. In places such as Alaska and Siberia, the thickness of permafrost is more than a kilometer. Scientists have estimated that the formation of permafrost under Barrow (Alaska) took more than half a million years. Studies have suggested that the thawing of permafrost is taking place at a fast rate as a result of the changes in climate due to global warming. The movement of water through the atmosphere, hydrosphere, geosphere, and biosphere is described by the water cycle. In simple words, the water cycle is the cycle of evaporation of water, and subsequent condensation and precipitation as rain and snow. Changes in energy are involved in the conversion of ice to water to water vapor, which is why the water cycle is considered to be a part of the energy cycle. The energy cycle describes how energy enters the ecosystem from the Sun, and is released as heat by the organisms into the biosphere. The transfer of energy through the Earth system determines the climate and weather patterns, which is essential for the availability of food and water. Several studies are being conducted to analyze the interactions between the cryosphere, atmosphere, hydrosphere, and biosphere. Studies suggest that the cryosphere can provide valuable information on climatic changes. In 2011, after examining satellite data for the last 20 years, scientists reported a rapid increase in the loss of ice from the ice sheets of Greenland and Antarctica. ➠ One of the major effects of the interactions between the cryosphere and hydrosphere is that, ice and snow melt into water, which becomes a part of the hydrosphere. Melting snow and glaciers provide billions of gallons of water every summer. ➠ As snow and ice are light in color, they reflect more of the Sun's energy back into space. Darker ocean and land become exposed due to the melting of snow and ice. The darker colors absorb and radiate the Sun's energy, thereby warming the atmosphere. Major climatic changes are taking place, as the amount of snow and ice that melts each summer is increasing because of global warming. ➠ Some living organisms within the biosphere are dependent on the components of the cryosphere for water. For instance, polar bears hunt for seals across the Arctic sea ice. Sea ice is also essential for the breeding cycle of certain species of penguins. Also, freshwater needed by certain plants and animals is provided by the melting of snow and ice. ➠ Greenhouse gases such as carbon dioxide and methane lie trapped in ice or frozen ground (permafrost) in the Arctic tundra. According to a research conducted by NASA, the permafrost soils have been warming by 2.7°F to 4.5°F in the past 30 years. This would cause the greenhouse gases to be released into the atmosphere. ➠ About 10.8% of the Earth's land surface is covered by perennial ice. A substantial portion of this ice is found in the ice sheets of Greenland and Antarctica. ➠ More than 15% of the land surface is covered by permafrost (permanently frozen ground). ➠ Majority of the freshwater ice (ice that forms on the rivers and lakes during winter) and snow cover is located in the Northern Hemisphere, as the land surfaces at higher altitudes are larger in the Northern Hemisphere. ➠ Snow cover is less extensive in the Southern Hemisphere, as the continents are located at lower latitudes (with the exception of Antarctica). ➠ Antarctica is covered by a huge ice sheet, and ice shelves and icebergs can be found in the ocean. ➠ Besides the Arctic region and Antarctica, there are places where it snows, and the ground, lakes, and rivers get frozen due to the dip in temperatures. For instance, frozen ground can be found at high elevations in mountains. On a concluding note, the cryosphere has a major effect on the climate, as snow and ice affect the heating and cooling over the surface of the Earth. If the cryosphere is adversely affected, the Earth would become warmer. As the energy balance of the Earth is affected, climate would change. Also, the melting of snow and ice at a faster rate would affect ocean currents, sea levels, as well as storm patterns. Thus, steps must be taken to prevent and control global warming.