Derived from the Greek word krios, meaning "cold", the cryosphere encompasses those parts of the Earth system that are subject to temperatures below 0°C for at least part of the year. Its largest components, by far, are the ice sheets in Greenland and Antarctica, but the cryosphere also includes:

• Ice caps and glaciers
• Sea ice
• Ice shelves
• Snow
• River and lake ice
• Frozen ground.

Together, these components play an important role in modulating the Earth's climate system. Snow and ice reflect a very high percentage of the radiation received from the sun, helping to regulate the planet's temperature. In addition, the spatial distribution of snow and ice is associated with longitudinal temperature differences, which drive winds and ocean currents.

Components of the cryosphere and their time scales. (Source: IPCC)

Although concentrated in the polar regions, elements of the cryosphere exist at nearly all latitudes, which make them useful indicators of global climate change. Taken together, all of the land-based ice contains approximately 75 percent of the Earth's freshwater. As this ice melts, most of the water produced makes its way to the ocean. Traditionally, this has been the focus of the NASA Cryospheric Science Program, as the Greenland and Antarctic ice sheets have the potential to raise global sea level by 7 and 57 meters (23 and 187 feet), respectively.

Cryospheric Science at NASA

Now, with long-term observations available from satellites and aircraft, better understanding of key relationships within the Earth system, and continual improvements in remote-sensing technologies, the current program has established the following objectives:

• To improve our understanding of the mechanisms controlling the mass balance and dynamics of the Greenland and Antarctic ice sheets, including interactions with the ocean and atmosphere.
• To develop, validate and improve predictive models of the contributions of land-based ice to sea-level change.
• To improve our understanding of the mechanisms controlling sea ice cover, including interactions with the ocean and atmosphere.
• To develop, validate and improve predictive models of changes in sea ice cover, and their implications for the Earth system.
• To improve estimates of snow accumulation on land-based and sea ice.

The Cryospheric Science Program is part of the Earth Sciences Division (ESD) in the Science Mission Directorate (SMD) at NASA Headquarters. It provides:

• Funding and oversight to competed, investigator-led, cryosphere-related scientific studies at universities, NASA centers and other institutions.
• Support to cryosphere-related satellite mission Science Teams.
• Support for the collection of cryosphere-related observations through the Airborne Sciences Program.
• Investment in the development of satellite and airborne cryosphere-related data products, including storage and distribution capabilities.

In addition, the program sponsors several polar initiatives designed to encourage interdisciplinary approaches to cryospheric science problems:

• Program for Arctic Regional Climate Assessment (PARCA)
• Sea-level Response to Ice Sheet Evolution (SeaRISE)
• West Antarctic Ice Sheet (WAIS), in partnership with the National Science Foundation (NSF)

Furthermore, NASA works closely with many interagency partners, especially the NSF's Office of Polar Programs, the National Oceanic and Atmospheric Administration (NOAA), the Department of Defense (DoD), the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL), and the United States Geologic Survey (USGS).

References

ACIA (2005), Arctic Climate Impact Assessment, Cambridge University Press, Cambridge, England, pp. 183-242.

Van der Veen, C. J. (1999), Fundamentals of Glacier Dynamics, A. A. Balkema, Rotterdam, Netherlands, pp. 1-6.