Geoscience Reference
In-Depth Information
Cryosphere
The areas of snow and ice, including the extended ice fields of Greenland and
Antarctica, other continental glaciers and snowfields, sea ice, and areas of permafrost,
are the Earth's cryosphere. The cryosphere has an important influence on climate
because of its high reflectivity to solar radiation. Continental snow cover and sea ice
have a market seasonally, and this can give rise to significant intra-annual and perhaps
interannual variations in the surface energy budgets of frozen polar oceans and conti-
nents with seasonal snow cover. Gradual warming in polar regions has the potential to
give rise to similar changes in surface energy balance over longer time periods. The
low thermal diffusivity of ice can also influence the surface energy balance at high lati-
tudes, because ice acts as an insulator inhibiting loss of heat to the atmosphere from
the underlying water and land. Near-surface cooling also gives rise to stable atmos-
pheres, which inhibit convection and contribute to cooler climates locally.
The large continental ice sheets do not change quickly enough to influence
seasonal or interannual climate much, but historical changes in ice sheet extent
and potential changes in the future extent of ice sheets are important because they
are associated with changes in sea level. If substantial melting of the continental ice
sheets occurs, altered sea level could change the boundaries of islands and
continents. Since many inhabited areas are close to such boundaries, sea level
change will likely have serious consequences for human welfare that are dispro-
portionate to the fractional area of land affected. The effect of global warming on
ice sheets is considered a major threat for this reason.
Lithosphere
The lithosphere, which includes the continents and the ocean floor, has an almost
permanent influence on the climatic system. There is large-scale transfer of
angular momentum through the action of torques between the oceans and the
continents. Continental topography affects air motion and global circulation
through the transfer of mass, angular momentum, and sensible heat, and the
dissipation of kinetic energy by friction in the atmospheric boundary layer.
Because the atmosphere is comparatively thin, organized topography in the form
of extended mountain ranges that lie roughly perpendicular to the preferred
atmospheric circulation, such as the Rocky Mountains in North America and the
Andes Mountains in South America, can inhibit how far maritime air penetrates
into continents and thus affect where clouds and precipitation occur.
The transfer of mass between the atmosphere and lithosphere is mainly as water
vapor, rain, and snow. However, this may sometimes also occur as dust when vol-
canoes throw matter into the atmosphere and increase the turbidity of the air. The
ejected sulfur-bearing gases and particulate matter may modify the aerosol load
and radiation balance of the atmosphere and influence climate over extended
areas. The soil moisture in the active layer of the continental lithosphere that is
