The difference is in how the glacier moves,
- Dry glaciers: In colder climates, basal melting is minimal or absent, and flow is entirely through ductile flow.
- Wet glaciers: In warmer climates, basal slip can predominate.
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In Antarctica, thermal regimes pass through the end members of cold, polythermal and warm (wet-based). This means that under some glaciers in cold environments, such as the Dry Valleys in Antarctica, pressure melting point is not reached and the glacier remains frozen to its bed.
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This is because a frozen glacier bed inhibits the rapid-flow mechanisms of sediment deformation, ice deformation and basal sliding.
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Between these two end members, polythermal glaciers have beds that are frozen and unfrozen. Many small glaciers in Svalbard are polythermal; cold temperatures mean that higher basal pressures must be reached to attain pressure melting point, and thin valley glaciers are typically frozen around their margins but wet-based in their upper reaches[20-22]
Glacial thermal regime
The confusion in that question was because the author of one of the books referred to the glacier below the firn line,
A line across the glacier, from edge to edge, that marks the transition between exposed glacier ice (below) and the snow-covered surface of a glacier (right).
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as being dry, which does not describe the glacier itself but how the snow would cover it.
