Antarctic Polar Regions | The world of Antarctic Ice | The Ice Caps

The speed of the glaciers : up to 1 km per year

The relief of the covered lands of the Antarctic being rugged, the ice caps are seeping slowly towards the extremities of the continent. The movement is relatively slow at the centre of the ice cap (just a few metres per year) but can reach a speed of about 100 metres per year at the coasts.

The Lambert Glacier, which is the largest glacier in the Antarctic at 400 kilometres long and 40 kilometres wide, is advancing at a speed of 1 kilometre per annum and churns out 35 cubic kilometres of ice each year in the form of icebergs.

Glaciology nevertheless concedes that between the moment when a particle of ice forms in the centre of the continental glacier and its arrival at the outer regions of its ice cap, 500,000 years could go by! Scientific research also is studying the way the Antarctic glaciers are seeping. Residual images from schoolday memories on the subject of rivers of ice in the Alps or Himalayas are quite inappropriate here.

Apart from gravity and weight, there are in fact several factors that influence the speed and direction of the seeping of the Antarctic glaciers: size, thickness and age of the glacier, the nature and shape of the bedrock over which it is moving, the declivity of the slope to which it is attached, the reigning temperatures at the interior and the slide conditions.

The glaciers progress in two ways :

  • Either by sliding on the bottom, in a direction materially perpendicular to the structural contour lines - for that a thin layer of water needs to exist between the base of the glacier and the bedrock. How is it that, in such a cold universe, water in its liquid state is to be found at 500 or indeed 1,000 metres of depth? Because at the interior of a glacier, the temperatures vary according to its thickness, its speed of progression, its snow-accumulation rate, and because the flow of heat emanating from the centre of the Earth (the geothermal flow) melts an average of 5 cm of ice each year.
  • Or, the second type of progression: pushed by the surface slope, the glacier becomes deformed like toothpaste or a pouring of melted chocolate. The thicker the ice and the steeper the slope, the more the ice will choose this second solution for its movement. As the ice is attached to its bed, the internal deformations that occur within the glacier will obey the physical laws of plastic deformation.