Executive summary by darmansjah
WATER Over 98
percent of the world’s fresh water is found in glaciers and ice caps.
Ice crumbling from the edges of the Perito Moreno glacier does
little to reduce the size of Patagonia’s Southern Ice Field, the third largest
glacial expanse in the world.
A glacier is a persistent body of dense ice exceeding a
surface area of 0.1 km² constantly moving under its own gravity; it forms where
the accumulation of snow exceeds its ablation (melting and sublimation) over
many years, often centuries. Glaciers slowly deform and flow due to stresses
induced by their weight, creating crevasses, seracs, and other distinguishing features.
They also abrade rock and debris from their substrate to create landforms such
as cirques and moraines. Glaciers form only on land and are distinct from the
much thinner sea ice and lake ice that form on the surface of bodies of water.
On Earth, 99% of glacial ice is contained within vast ice
sheets in the polar regions, but glaciers may be found in mountain ranges on
every continent, and on a few high-latitude oceanic islands. Between 35°N and
35°S, glaciers occur only in the Himalayas, Andes, a few high mountains in East
Africa, Mexico, New Guinea and on Zard Kuh in Iran.
Glacial ice is the largest reservoir of freshwater on
Earth.Many glaciers from temperate, alpine and seasonal polar climates store
water as ice during the colder seasons and release it later in the form of
meltwater as warmer summer temperatures cause the glacier to melt, creating a
water source that is especially important for plants, animals and human uses
when other sources may be scant. Within high altitude and Antarctic environments,
the seasonal temperature difference is often not sufficient to release
meltwater.
Because glacial mass is affected by long-term climate
changes, e.g., precipitation, mean temperature, and cloud cover, glacial mass
changes are considered among the most sensitive indicators of climate change
and are a major source of variations in sea level.
No comments:
Post a Comment