Cryosphere

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Cryosphere

Introduction

The cryosphere refers to the areas of Earth that are covered by ice and snow. These are primarily located near the poles and at high altitudes. The cryosphere includes ice and snow that is seasonal and short-term, such as frozen freshwater lakes and snow cover. It also includes areas of long-lasting ice such as the polar ice caps, glaciers, and permafrost. The word cryosphere comes from the Greek word kryos, meaning cold.

The role of the cryosphere in climate change is not yet clear, as complex feedback mechanisms make predicting impacts on the relationship between climate change and changes in the cryosphere difficult to achieve. However, the cryosphere is thought to play a role in enhancing climate change, as well as acting as an early indicator of climate change. Most scientists agree on two observations: mean global temperatures have risen at an increasing rate over the past several decades, and the amount of Earth's snow and ice cover has decreased over the same period.

Historical Background and Scientific Foundations

The Intergovernmental Panel on Climate Change (IPCC) noted in its report Climate Change 2001: The Scientific Basis that the inclusion of the cryosphere in global climate models is rudimentary. However, the cryosphere is also considered to be an early indicator of climate change, with melting glaciers, melting ice caps, and reduced snowfalls being signs of the impact of global warming.

WORDS TO KNOW

ALBEDO: A numerical expression describing the ability of an object or planet to reflect light.

INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE (IPCC): Panel of scientists established by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) in 1988 to assess the science, technology, and socioeconomic information needed to understand the risk of human-induced climate change.

MEAN: A measure of central tendency (average) found by adding all the terms in a set and dividing by the number of terms.

PERMAFROST: Perennially frozen ground that occurs wherever the temperature remains below 32°F (0°C) for several years.

POLAR ICE CAP: Ice mass located over one of the poles of a planet not otherwise covered with ice. In our solar system, only Mars and Earth have polar ice caps. Earth's north polar ice cap has two parts, a skin of floating ice over the actual pole and the Greenland ice cap, which does not overlay the pole. Earth's south polar ice cap is the Antarctic ice sheet.

SOLAR RADIATION: Energy received from the sun is solar radiation. The energy comes in many forms, such as visible light (that which we can see with our eyes). Other forms of radiation include radio waves, heat (infrared), ultraviolet waves, and x-rays. These forms are categorized within the electromagnetic spectrum.

Impacts and Issues

A major issue with the cryosphere is the high albedo of snow compared to land, and sea ice compared to the sea. On land, the high albedo (reflective fraction) of snow causes more solar radiation to be reflected from Earth. Without snow cover, more solar radiation is absorbed by land, and this enhances the warming effect. The same occurs for sea ice, where sea ice reflects more solar radiation than seawater. Without frozen sea ice present, a greater amount of radiation is absorbed and the warming effect is enhanced. This suggests that the cryosphere could play a role in accelerating global warming.

Sea ice also impacts ocean circulation because it contains less salt than seawater, and its formation increases the salinity and density of surface water. This density difference between surface water and deep water drives ocean circulation. With less sea ice forming, this ocean circulation could be reduced, which would then also influence the redistribution of heat.

The cryosphere also plays a role in providing freshwater to regions throughout the world. Melting snow and melting glaciers are a major source of freshwater throughout Europe, North America, South America, and Asia. Reductions in snowfall and changes in the melting patterns of snow and glaciers could have a significant impact on global freshwater supplies.

BIBLIOGRAPHY

Books

Houghton, J. T., et al, eds. Climate Change 2001: The Scientific Basis. Cambridge: Cambridge University Press, 2001.

Web Sites

“1999 EOS Science Plan: Cryospheric Systems.” National Aeronautics and Space Administration (NASA), November 8, 2007. < http://eospso.gsfc.nasa.gov/science_plan/Ch6.pdf> (accessed November 8, 2007).

“Special Report on the Regional Impacts of Climate Change: An Assessment of Vulnerability.” Intergovernmental Panel on Climate Change (IPCC). < http://www.grida.no/climate/ipcc/regional/index.htm> (accessed October 15, 2007).

“Our Planet.” United Nations Environment Programme (UNEP), May 2007. < http://www.unep.org/pdf/Ourplanet/2007/may/en/OP-2007-05-en-FULLVERSION.pdf> (accessed November 6, 2007).

Tony Hawas

Climate Change: In Context