Ice stream

[2] They can move upwards of 1,000 metres (3,300 ft) a year, and can be up to 50 kilometres (31 mi) in width, and hundreds of kilometers in length.

[3] They tend to be about 2 km (1.2 mi) deep at the thickest, and constitute the majority of the ice that leaves the sheet.

Most ice streams contain a layer of water at the bottom, which lubricates flow and acts to increase speed.

In addition to thickness, water, and stresses, sediment and bedrock play a key role in the rate at which ice streams drain.

If the underlying sediment is too porous, allowing for too much water to seep into it, and therefore become saturated, it will be incapable of supporting the shear stress the ice stream places on the bed.

Flow velocity of the ice stream is not entirely constant, but in short time scales of days to weeks, it can be treated as such, over long scales, however, it is variable, depending on how the conditions of thickness, temperature, water accumulation, stresses, and base material have changed.

[6] Geomorphic features such as bathymetric troughs indicate where paleo-ice streams in Antarctica extended during the Last Glacial Maximum (LGM).

[8] This notion is important when considering how the underlying geomorphology of ice streams control at what rate and how they retreat.

Furthermore, this reinforces the importance of internal factors such as bed characteristic, slope, and drainage basin size in determining ice stream dynamics.

Further upstream, the initiation of the ice stream (established by looking at velocity data) is caused by a weak bed.

[13] In Iceland, areas with reticulated ridges, ribbed moraines, and trunk-flow zones have demonstrated no control over the direction and magnitude of ice streams.