Cryosphere

Definition

The (from the Greek kryo, meaning “too cold”) refers to those parts of the Earth’s surface where temperatures are sufficiently low that water is frozen solid, in the form of either snow or ice. The conditions that freeze the available water within a particular area can be seasonal or can last for years or centuries. The cryosphere includes land covered with snow in the winter; freshwater lakes and river systems that freeze over seasonally; glaciers that freely move about larger water systems and are thus prone to melting and reshaping; and permafrost, or frozen soil and rock that remains frozen year round. The places most associated with the cryosphere are the North and South Poles, but frozen surfaces are found in many high-elevation regions of both the Northern and Southern Hemispheres.

Scientists distinguish two types of formations that make up the cryosphere: land ice and sea ice. Land ice is formed slowly by compressed snow that becomes layers of ice. Land ice is thus freshwater. Perhaps the most familiar examples of land ice are glaciers, great slow-moving ice masses that store at any one time close to 70 percent of the world’s available freshwater. Other examples of land ice are ice shelves left where glaciers break off and head into the open oceans as icebergs; ice shelves are found in coastal areas of Greenland, northern Canada, northern China, lower South America, southern Australia, and, of course, both poles.

Conversely, the polar oceans, both north and south, are covered with sea ice, or frozen seawater. floats on the surface of the water and has an average thickness of 1 meter in the Antarctic and nearly 3 meters in the Arctic. Because this ice exists within a dynamic environment—that is, one subject to temperature changes, wind, and ocean currents—sea ice can be measured by its duration (generally one year or multiyear). Because navigation depends on charting these fluid conditions, climatologists measure the sea ice as it cracks and even splits into huge moving parts, particularly as it inevitably diminishes during the abbreviated summer seasons at the poles. In the most extreme reaches of both poles, sea ice survives summer melting and becomes far thicker and can measure up to 381 centimeters.

Significance for Climate Change

Although seasonal fluctuations in mean temperatures in polar regions are to be expected and do not affect the general dynamic of the cryosphere, long-term climate shifts resulting from decades of burning have contributed to a significant rise in the Earth’s average air temperature. This global warming, in turn, affects the thousands of square kilometers that make up the cryosphere. As that fragile environment undergoes radical changes over a relatively brief period of time, such changes, in turn, affect a variety of climate and meteorological conditions around the globe. Interest in the cryosphere has greatly increased over the last generation, as climatologists see this frozen environment as the earliest indicator of rising global temperatures. The National Snow and Ice Data Center at the University of Colorado monitors the cryosphere.

Most dramatically, the diminishing of the snow and ice cover and the shortening of the winter season at the poles means that the planet’s natural insulation from the direct bombardment of solar energy is diminishing. The bright surface of the snow and ice of the cryosphere contributes to Earth’s albedo and is responsible for reflecting back into space 70 percent of the Sun’s energy. As that protection recedes, the Earth absorbs more solar energy, resulting in an increase in mean air temperature.

The global warming trend causes inland waterways to thaw earlier than they otherwise would, disrupting navigation lines and storm patterns and affecting the ecosystems of indigenous wildlife and plants. Groundwater levels in turn decline. Glaciers melt, and scientists must confront the possibility of significant impacts on the Earth’s water system and the need for global water management. There is cause for concern: Scientists estimate that global sea levels have risen over the last two decades by 7.5 to 10 centimeters, but the loss of significant ice in the endangered Antarctic could raise ocean levels a catastrophic 9 meters in the next century, making nearly 15 percent of the world’s population who live along shorelines climate refugees.

The sea-ice shelves—which protect coastlines in both poles from wave erosion along with Alaska, Canada, and Russia—are disappearing, upending people who have worked in that difficult environment for centuries. In turn, under the impact of rising air temperatures, the loses its integrity, a process further complicated by the drilling into the rich deposits of fossil fuels. But loss of the permafrost has a greater significance. Trapped within its thousands of frozen kilometers are centuries of decayed plant and animal detritus. As the permafrost thaws, carbon dioxide and methane, themselves greenhouse gases, are released in great volume to further influence global air temperature.

Bibliography

Archer, David. The Long Thaw: How Humans Are Changing the Next 100,000 Years of Earth’s Climate. Princeton, N.J.: Princeton University Press, 2008.

Flannery, Tim. We Are the Weather Makers: The Story of Global Warming. Rev. ed. London: Penguin, 2007.

Michaels, Patrick J. Climate of Extremes: Global Warming Science They Don’t Want You to Know. Washington, D.C.: Cato Institute, 2009.

Slaymaker, Olav, and Richard Kelly. The Cryosphere and Global Environmental Change. Hoboken, N.J.: Wiley-Blackwell, 2007.

"State of the Cryosphere Report 2024." UNESCO, 13 Nov. 2024, www.unesco.org/en/articles/state-cryosphere-report-2024. Accessed 13 Dec. 2024.