Future Earth and the Cryosphere

The term "cryosphere" (deriving from the Greek word kryos for frost or icy cold) is used to describe collect­ively those portions of the Earth's surface where water is in a solid form. It includes sea, lake, and river ice, snow cover, glaciers, ice caps and ice sheets, and frozen ground (including permafrost). While the focus of this chapter is on geodetic issues and Future Earth, which primarily involves ice sheets and glaciers on land and their role in global mass redistribution and sea level, the cryosphere as a whole is an integral part of the global climate system with important links and feedbacks gen­erated through its influence on surface energy and mois­ture fluxes, clouds, precipitation, hydrology, and atmospheric and oceanic circulation. The basic proper­ties that determine these roles are the high albedo of snow and ice surfaces; the latent heat involved in phase changes of ice/water; the height-mass balance feedback, which results from the great elevation of ice sheets and resultant effects on temperature and precipitation; and the insulating effect of snow cover on land and of floating ice on fresh water or seawater. Other major factors include the water volume stored in ice sheets and glaciers, the greenhouse gases locked up in perma­frost, and the delays in annual energy and water cycles due to seasonal snow and ice cover. Through these and associated feedback processes, the cryosphere plays a significant role in global climate. Cryospheric processes therefore need to be included explicitly and correctly in climate models to project future response to global change. Change in the cryosphere is also an important indicator of climate variability and change.