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Nature 444, 1063-1064 (21 December 2006) | doi:10.1038/nature05430; Received 18 April 2006; Accepted 9 November 2006

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Fortnightly variations in the flow velocity of Rutford Ice Stream, West Antarctica

G. Hilmar Gudmundsson1

  1. British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK

Correspondence to: G. Hilmar Gudmundsson1 Correspondence and requests for materials should be addressed to the author (Email: ghg@bas.ac.uk).

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Most of the ice lost from the Antarctic ice sheet passes through a few fast-flowing and highly dynamic ice streams1. Quantifying temporal variations in flow in these ice streams, and understanding their causes, is a prerequisite for estimating the potential contribution of the Antarctic ice sheet to global sea-level change2, 3. Here I show that surface velocities on a major West Antarctic Ice Stream, Rutford Ice Stream, vary periodically by about 20 per cent every two weeks as a result of tidal forcing. Tidally induced motion on ice streams has previously been thought to be limited to diurnal or even shorter-term variations4, 5, 6, 7, 8, 9. The existence of strong fortnightly variations in flow demonstrates the potential pitfalls of using repeated velocity measurements over intervals of days to infer long-term change.

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