Ice Shelf

ice shelf [′īs ‚shelf]

(oceanography)

A thick sheet of ice with a fairly level or undulating surface, formed along a polar coast and in shallow bays and inlets, fastened to the shore along one side but mostly afloat and nourished by annual accumulation of snow and by the seaward extension of land glaciers.

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Ice Shelf 

a glacier that is floating or partially resting on the bottom and flowing from the shore into the sea in the form of a plate that diminishes in thickness toward the edge and terminates in a cliff.

The ice shelf is a continuation of land ice sheets. More rarely, it is formed by the accumulation of snow on sea ice and by the cementing together of accumulations of icebergs by snow and ice. Ice shelves are found almost exclusively in Antarctica. Their total area is 1,460,000 sq km; the volume is about 0.6 million cu km; and the thickness varies from 200–1,300 m at the land edge to 50–400 m at the sea edge. The accumulation area usually encompasses the entire upper surface and the coastal section of the lower surface where ice forms; in the marginal zone the ice melts on the bottom (up to 1 m per year). A large part of the loss occurs from the breaking off of icebergs (a volume at times of thousands of cu km). The rate of movement of the ice shelf, which increases toward the edge, varies from 300–800 m to 1,800 m and more per year. (The largest ice shelf is the Ross Ice Shelf.)

REFERENCES

Shumskii, P. A. “Oledenenie Antarktidy.” In the collection Osnovnye itogi izucheniia Antarktiki za 10 let. Moscow, 1967.
Atlas Antarktiki, vol. 2. Leningrad, 1969.