The Cryosphere and Climate Change: The main components of the cryosphere are snow, river and lake ice, sea ice, glaciers and ice caps, ice shelves, ice sheets, and frozen ground (Figure below). In terms of the ice mass and its heat capacity, the cryosphere is the second largest component of the climate system (after the ocean). Its relevance for climate variability and change is based on physical properties, such as its high surface reflectivity (albedo) and the latent heat associated with phase changes, which have a strong impact on the surface energy balance.
The cryosphere on land stores about 75% of the world’s freshwater. The volumes of the Greenland and Antarctic Ice Sheets are equivalent to approximately 7 m and 57 m of sea level rise, respectively. Changes in the ice mass on land have contributed to recent changes in sea level. On a regional scale, many glaciers and ice caps play a crucial role in freshwater availability. Presently, ice permanently covers 10% of the land surface, of which only a tiny fraction lies in ice caps and glaciers outside Antarctica and Greenland. Ice also covers approximately 7% of the oceans in the annual mean. In midwinter, snow covers approximately 49% of the land surface in the Northern Hemisphere (NH). Frozen ground has the largest area of any component of the cryosphere. All parts of the cryosphere contribute to short-term climate changes, with permafrost, ice shelves and ice sheets also contributing to longer-term changes including the ice age cycles.
The Cryosphere and Climate Change The Cryosphere and Climate Change.
Observations show a global-scale decline of snow and ice over many years, especially since 1980 and increasing during the past decade, despite growth in some places and little change in others. Most mountain glaciers are getting smaller. Snow cover is retreating earlier in the spring. Sea ice in the Arctic is shrinking in all seasons, most dramatically in summer.
Reductions are reported in permafrost, seasonally frozen ground and river and lake ice. Important coastal regions of the ice sheets on Greenland and West Antarctica, and the glaciers of the Antarctic Peninsula, are thinning and contributing to sea level rise. The total contribution of glacier, ice cap and ice sheet melt to sea level rise is estimated as 1.2 ~+mn~ 0.4 mm for each year during the period 1993 to 2003.
Reductions in snow cover and in mountain glaciers have occurred despite increased snowfall in many cases, implicating increased air temperatures. Similarly, although snow cover changes affect frozen ground and lake and river ice, this does not seem sufficient to explain the observed changes, suggesting that increased local air temperatures have been important. Observed arctic sea ice reductions can be simulated fairly well in models driven by historical circulation and temperature changes.
The observed increases in snowfall on ice sheets in some cold central regions, surface melting in coastal regions and sub-ice-shelf melting along many coasts are all consistent with warming. The geographically widespread nature of these snow and ice changes suggests that widespread warming is the cause of the Earth’s overall loss of ice.
The Cryosphere and Climate Change is sourced from the International Panel on Climate Change, Working Group 1, The Physical Science Basis, Observations: Changes in Snow, Ice and Frozen Ground Chapter 4)
A Tour of the Cryosphere – This animation portrays fluctuations in the cryosphere through observations collected from a variety of satellite-based sensors. The animation begins in Antarctica, showing ice thickness ranging from 2.7 to 4.8 kilometers thick along with swaths of polar stratospheric clouds. In a tour of this frozen continent, the animation shows some unique features of the Antarctic landscape found nowhere else on earth. Ice shelves, ice streams, glaciers, and the formation of massive icebergs can be seen. A time series shows the movement of iceberg B15A, an iceberg 295 kilometers in length which broke off of the Ross Ice Shelf in 2000. Moving farther along the coastline, a time series of the Larsen ice shelf shows the collapse of over 3,200 square kilometers ice since January 2002. As we depart from the Antarctic, we see the seasonal change of sea ice and how it nearly doubles the size of the continent during the winter.
Video source: NASA/Goddard Space Flight Center Scientific Visualization Studio. The Cryosphere and Climate Change.
See Also
