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Impacts of warm water on Antarctic ice shelf stability through basal channel formation

Abstract

Antarctica’s ice shelves provide resistance to the flow of grounded ice towards the ocean. If this resistance is decreased as a result of ice shelf thinning or disintegration1, acceleration of grounded ice can occur, increasing rates of sea-level rise. Loss of ice shelf mass is accelerating, especially in West Antarctica, where warm seawater is reaching ocean cavities beneath ice shelves2. Here we use satellite imagery, airborne ice-penetrating radar and satellite laser altimetry spanning the period from 2002 to 2014 to map extensive basal channels in the ice shelves surrounding Antarctica. The highest density of basal channels is found in West Antarctic ice shelves. Within the channels, warm water flows northwards, eroding the ice shelf base and driving channel evolution on annual to decadal timescales. Our observations show that basal channels are associated with the development of new zones of crevassing, suggesting that these channels may cause ice fracture. We conclude that basal channels can form and grow quickly as a result of warm ocean water intrusion, and that they can structurally weaken ice shelves, potentially leading to rapid ice shelf loss in some areas.

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Figure 1: Distribution and examples of basal channel types around the Antarctic continent.
Figure 2: Growing channel on the Getz Ice Shelf.
Figure 3: Ice shelf fracture at the tip of the Scott Peninsula, Getz Ice Shelf.

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Acknowledgements

This study was supported by NASA through a NASA Earth Science Student Fellowship (NNX14AK82H) and grant NNX13AP60, and by USGS contract G12PC00066. We thank A. Le Brocq for providing subglacial hydrology data, and S. Schmidtko and L. Padman for ocean temperature data. We would also like to acknowledge assistance with figures from A. Pope, and helpful suggestions from O. Sergienko, R. Alley and C. Shuman.

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K.E.A. led the writing, image analysis and compilation of graphics and tables, and with T.A.S., H.A.F. and M.R.S. conducted the ICESat-based elevation change analysis. All co-authors contributed to the writing of the paper.

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Correspondence to Karen E. Alley.

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The authors declare no competing financial interests.

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Alley, K., Scambos, T., Siegfried, M. et al. Impacts of warm water on Antarctic ice shelf stability through basal channel formation. Nature Geosci 9, 290–293 (2016). https://doi.org/10.1038/ngeo2675

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