||Snow, Ice And
||The three different phases of H2O
are the major driving forces that form the landscape and determine
the biology and human occupation. Over millenia, snowfall has accumulated
and packed down to form the great ice caps and glaciers of the Arctic.
The annual layers now form the 'frozen archive' that scientists
are exploiting to chart the climate history, especially on the vast
mass of the Greenland Icecap. This icecap is up to 3000m deep and
virtually the largest freshwater reservoir in the North.
||Icecaps spill over to form the glaciers.
These are pushed down slope by the pressure from above, moving by
up to 30 metres a year, grinding away the rock surface, picking
up debris and transporting it to the glacier tongue where it is
deposited as lateral or terminal moraines, or transported away by
melt water. The melt water forms the streams and rivers, deep and
fast flowing where the terrain is steep, wider and slower on flatter
landscapes where the water spreads over the floodplain. Over large
areas, water from glaciers and snow melt contributes to the many
thousands of ponds and lakes and the wetlands which are such a feature
of much of the Arctic.
|But it is the permafrost - another
water store - which prevents the water from draining into the deeper
layers of soil and rock (see figure 9).
So, even with the very low snowfall, less than 300mm in continental
areas, the landscape is usually dominated by water. The exception
is where stony ground provides drainage, drought conditions inhibit
plant growth, and the polar deserts occur. One reason why the snowfall
is so low is that cold air carries much less water than warm air.
So, near the coast, warm air comes off the sea, it is cooled by
the land, especially where it is forced to rise by mountains, and
the moisture in clouds is deposited as rain or snow. Thus, whilst
coastal areas may be warmer, they have precipitation of up to 3000mm.
A consequence of the relationship between temperature and the water
holding capacity of air is that climate warming is likely to be
linked to increased snow and rain, especially near the coast.