Net retreat of Antarctic glacier grounding lines

Abstract

Grounding lines are a key indicator of ice-sheet instability, because changes in their position reflect imbalance with the surrounding ocean and affect the flow of inland ice. Although the grounding lines of several Antarctic glaciers have retreated rapidly due to ocean-driven melting, records are too scarce to assess the scale of the imbalance. Here, we combine satellite altimeter observations of ice-elevation change and measurements of ice geometry to track grounding-line movement around the entire continent, tripling the coverage of previous surveys. Between 2010 and 2016, 22%, 3% and 10% of surveyed grounding lines in West Antarctica, East Antarctica and at the Antarctic Peninsula retreated at rates faster than 25 m yr−1 (the typical pace since the Last Glacial Maximum) and the continent has lost 1,463 km2 ± 791 km2 of grounded-ice area. Although by far the fastest rates of retreat occurred in the Amundsen Sea sector, we show that the Pine Island Glacier grounding line has stabilized, probably as a consequence of abated ocean forcing. On average, Antarctica’s fast-flowing ice streams retreat by 110 metres per metre of ice thinning.

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Fig. 1: Rates of grounding-line migration between 2010 and 2016 along the Antarctic grounding line8 derived from CryoSat-2 and bedrock topography24 observations.
Fig. 2: Continuation of rates of grounding-line migration in the Amundsen Sea11,12 by our approach.
Fig. 3: Rates of grounding-line migration versus rates of surface elevation.

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Acknowledgements

We acknowledge the European Space Agency (ESA) for the provision of CryoSat-2 data and ESA’s Antarctic_Ice Sheet_cci, as well as the UK Natural Environment Research Council’s (NERC) Centre for Polar Observation and Modelling (CPOM) for processing of these data. H.K. was funded through the NERC’s iSTAR Programme and NERC Grant Number NE/J005681/1. A.E.H. was supported by an independent research fellowship (no. 4000112797/15/I-SBo) jointly funded by ESA, the University of Leeds and the British Antarctic Survey. The figures were produced using the Generic Mapping Tool (https://doi.org/10.1029/90EO00319).

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H.K., A.S., A.E.H. and M.M. designed the study. L.G. and A.M. processed CryoSat-2 data. H.K., A.S., A.E.H., M.M. and T.S. analysed the results. H.K. and A.S. wrote the manuscript. All authors contributed to revising the manuscript.

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Correspondence to Hannes Konrad.

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Supplementary information

Supplementary Information

Supplementary Figures, Table 1 and References.

Supplementary Table 2

Surface elevation and grounding-line migration

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Konrad, H., Shepherd, A., Gilbert, L. et al. Net retreat of Antarctic glacier grounding lines. Nature Geosci 11, 258–262 (2018). https://doi.org/10.1038/s41561-018-0082-z

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