Extent and basal characteristics of the M'Clintock Channel Ice Stream

The M'Clintock Channel Palaeo Ice Stream drained the northwestern margin (Victoria Island, Arctic Canada) of the Laurentide Ice Sheet, functioning for 200 years prior to 10 ka BP. From its bed imprint. it is reconstructed as 720 x 140 km with a cross-sectional area of 100 km(2), comparable in size to the Hudson Strait Ice Stream. It drained an estimated 80,000 km(3) of ice, enough to significantly affect the shrinking ice sheet and drive the Keewatin ice divide south-eastwards. Such discharges likely produced Heinrich events and influenced the temperature and salinity of the Western Arctic Ocean. Ice stream location was controlled by a topographic trough, but glaciological regulation, rather than properties of the bed, controlled margin locations and hence ice stream width. The ice stream eroded into pre-existing unconsolidated sediments and left a pattern of subglacially produced landforms, recording a snapshot view of the bed prior to shutdown. Frictional-shutdown occurred once downcutting through sediments reached bedrock in places. High sediment availability appears critical for ice stream functioning, with a drift thickness of 50 m required to sustain its similar to 200 year lifespan. Debris discharge was exceptionally high (73,000 m(3) a(-1)m(-1)). This ice stream demonstrates non-steady response of ice sheets to climate change and their large impact on mass balance and stability of ice sheets. (C) 2001 Elsevier Science Ltd and INQUA. All rights reserved.