Abstract
Ice flow acceleration has played a crucial role in the rapid retreat of calving glaciers in Alaska1,2, Greenland and Antarctica3,4. Glaciers that calve in water flow much faster than those that terminate on land, as a result of enhanced basal ice motion where basal water pressure is high5. However, a scarcity of subglacial observations in calving glaciers limits a mechanistic understanding. Here we present high-frequency measurements of ice speed and basal water pressures from Glaciar Perito Moreno, a fast-flowing calving glacier in Patagonia. We measured water pressure in boreholes drilled at a site where the glacier is 515±5 m thick, and where more than 60% of the ice is below the level of proglacial lakes. We found that the mean basal water pressure was about 95% of the pressure imposed by the weight of the overlying ice. Moreover, changes in basal water pressure by a few per cent drove nearly 40% of the variations in ice flow speed. The ice speed was strongly correlated to air temperature, suggesting that glacier motion was modulated by water pressure changes as meltwater entered the system. We conclude that basal water pressure in calving glaciers is important for glacier dynamics, and closely connected to climate conditions.
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Acknowledgements
We thank the members of the field campaign at Glaciar Perito Moreno in 2008/2009 and 2010 for their help on the glacier. Hielo y Aventura S. A. offered logistic support and Gendarmeria Nacional Argentina operated helicopter transportation. Drilling equipment was constructed by the workshop of the Institute of Low Temperature Science, Hokkaido University. Thanks are extended to R. Greve and H. Blatter for comments on the manuscript. This research was funded by the Japanese Ministry of Education, Science, Sports and Culture, Grant-in-Aid 18251002 (2005–2009) and 23403006 (2011–2014).
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S.S., P.S. and M.A. designed the research. S.S., N.N., H.E. and K.T. drilled the boreholes. S.S., P.S., N.N., S.T., K.T. and S.M. collected the water pressure and GPS data. S.S. analysed the data and wrote the manuscript. The authors discussed the results and commented jointly on the manuscript.
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Sugiyama, S., Skvarca, P., Naito, N. et al. Ice speed of a calving glacier modulated by small fluctuations in basal water pressure. Nature Geosci 4, 597–600 (2011). https://doi.org/10.1038/ngeo1218
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DOI: https://doi.org/10.1038/ngeo1218