Glacier ice accumulation occurs through accumulation of
snow and other frozen
precipitation, as well as through other means including
rime ice (freezing of
water vapor on the
glacier surface),
avalanching from
hanging glaciers on cliffs and mountainsides above, and re-freezing of glacier
meltwater
Meltwater is water released by the melting of snow or ice, including glacial ice, tabular icebergs and ice shelves over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reducing. Meltwater can be ...
as
superimposed ice
Superimposition is the placement of one thing over another, typically so that both are still evident.
Graphics
In graphics, superimposition is the placement of an image or video on top of an already-existing image or video, usually to add to t ...
. Accumulation is one element in the
glacier mass balance formula, with
ablation counteracting. With successive years in which accumulation exceeds ablation, then a glacier will experience positive
mass balance, and its
terminus will advance.
Accumulation zones
Glaciologists subdivide glaciers into glacier accumulation zones, based on the melting and refreezing occurring. These zones include the dry snow zone, in which the ice entirely retains subfreezing temperatures and no melting occurs. Dry snow zones only occur within the interior regions of the
Greenland and
Antarctica ice sheets.
Below the dry snow zone is the
percolation zone, where some meltwater penetrates down into the glacier where it refreezes. In the wet snow zone, all the seasonal snow melts. The meltwater either percolates into the depths of the glacier or flows down-glacier where it might refreeze as superimposed ice. A glacier's
equilibrium line is located at the lower limit of the wet snow zone.
See also
*
Glacier growing
Glacier growing, artificial glaciation or glacier grafting, is a practice carried out in the Hindu Kush and Himalaya regions aimed at creating small new glaciers to increase water supply for crops and in some cases to sustain micro hydro power. In ...
References
{{glaciers
Glaciology