Climate Change in the Arctic - The Changing Arctic Environment: The Arctic Messenger - page 280

Snow and Permafrost
A great deal of freshwater in the Arctic is locked up in soils as permafrost and in snow. How
are these two reservoirs faring with a general circumpolar trend towards more precipitation
and shorter and warmer winters? The quick and general answer is that substantial decreases
in snow cover are taking place.
The largest and most rapid decreases in snow water equivalent (the amount of water
contained within the snowpack) and in snow cover duration has occurred in Arctic maritime
regions, with the highest precipitation being recorded in Alaska, northern Scandinavia and
the north-east Pacific coast of Russia. However, although this trend has been obvious in the
North American Arctic record since the 1950s, it has only been evident in some Eurasian
records since about 1980. In some Eurasian regions, snow depths are actually increasing.
Most of the decrease in snow cover duration occurs in the spring, which is the response
expected with regional climate warming, snow albedo effects (albedo decreases as soon as
melting begins) and the albedo-reducing impact of accumulations of black carbon. Once
again, we are looking at positive feedback mechanisms that promote accelerated warming.
As soon as the snow has gone, the darker surface reflects little of the sun's energy back into
space and the darker terrain absorbs more energy.
ThesereductionsinArcticspringsnowcoveralsohavewideimplicationsfortheArctic
ecosystem, including growing season length, the timing and nature of spring river runoff,
wildlife ecology and the ground thermal regime. The upper layer of soil and rock in the
High Arctic that can freeze and thaw seasonally is called the active zone . It can be up to 10
metres thick. Below this is the permafrost. This is a layer of frozen ice, rock and soil/sedi-
ment that remains below 0°C for two or more consecutive years. You will find it underlying
most of the terrestrial Arctic and even find it below some Arctic shelf seas. Permafrost var-
ies in thickness from a few centimetres at its southern limits to as much as 1,500 metres in
Siberia. As you travel south, it does not abruptly end but continues as diminishing islands of
ice known as discontinuous permafrost . Saline water in soil freezes below 0°C. This creates