Glacier velocity variability due to rain-induced sliding and cavity formation

Huw J. Horgan, Brian Anderson, Richard B. Alley, Calum J. Chamberlain, Robert Dykes, Laura M. Kehrl, John Townend

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


The largest accelerations of glaciers and ice sheets are caused by changes in basal slip. Here we examine glacier speed and rain-induced accelerations using a near-continuous 26-month-long GNSS time series from a large maritime glacier (Tasman Glacier, New Zealand). During periods of high rain-rate we observe short-term increases in 24-hour speeds to up to 15-times background speed. Speeds calculated over 3-hour intervals increase to up to 36-times background speed. Acceleration events correspond with times when bed separation also increases rapidly indicating that the acceleration is associated with the growth of water-filled cavities at the bed. Glacier speeds then decrease prior to the reduction in bed separation, indicating cavity growth, not cavity extent, controls the acceleration. The short-term accelerations are superimposed on longer-term periods of enhanced velocity that persist for days to weeks and decay at similar rates to bed separation estimates and proglacial lake levels. A power-law relationship between observed rain-rate and speed exists at the glacier front and exhibits no apparent upper bound. Overall, we estimate that rain-induced accelerations account for 11-14% of Tasman Glacier's displacement during the observation period. The rain-rate-velocity relationship and the rainfall record since 2001 indicate that rain-induced speed-up events result in interannual variability in glacier displacement of 2%-13%.

Original languageEnglish (US)
Pages (from-to)273-282
Number of pages10
JournalEarth and Planetary Science Letters
StatePublished - Dec 15 2015

All Science Journal Classification (ASJC) codes

  • Geochemistry and Petrology
  • Geophysics
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)


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