Limits in detecting acceleration of ice sheet mass loss due to climate variability

Abstract

The Greenland and Antarctic ice sheets have been reported to be losing mass at accelerating rates1,2. If sustained, this accelerating mass loss will result in a global mean sea-level rise by the year 2100 that is approximately 43 cm greater than if a linear trend is assumed2. However, at present there is no scientific consensus on whether these reported accelerations result from variability inherent to the ice-sheet–climate system, or reflect long-term changes and thus permit extrapolation to the future3. Here we compare mass loss trends and accelerations in satellite data collected between January 2003 and September 2012 from the Gravity Recovery and Climate Experiment to long-term mass balance time series from a regional surface mass balance model forced by re-analysis data. We find that the record length of spaceborne gravity observations is too short at present to meaningfully separate long-term accelerations from short-term ice sheet variability. We also find that the detection threshold of mass loss acceleration depends on record length: to detect an acceleration at an accuracy within ±10 Gt yr−2, a period of 10 years or more of observations is required for Antarctica and about 20 years for Greenland. Therefore, climate variability adds uncertainty to extrapolations of future mass loss and sea-level rise, underscoring the need for continuous long-term satellite monitoring.

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Figure 1: Recent mass changes of the Greenland and Antarctic ice sheets.
Figure 2: Trend and acceleration uncertainty for Greenland.
Figure 3: Trend and acceleration uncertainty for Antarctica.

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Acknowledgements

The GRACE processing centres are acknowledged for processing and sharing the GRACE data. We thank G. A, R. Riva and P. Stocchi for providing glacial isostatic adjustment models and E. Rignot for the Greenland ice discharge data. B.W. is financially supported by a Marie Curie International Outgoing Fellowship within the 7th European Community Framework Programme (FP7-PEOPLE-2011-IOF-301260). I.S. would like to acknowledge support from the German Research Foundation (DFG) through grant SA 1734/2-2. J.L.B. was supported by NERC grant NE/I027401/1.

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B.W. developed the idea and methodology and wrote the article. I.S. provided the GRACE data for Antarctica, J.T.M.L. and M.R.v.d.B. provided the SMB data and J.L.B. developed the methodology to calculate the ice discharge. All authors discussed and commented on the manuscript and methodology.

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Correspondence to B. Wouters.

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The authors declare no competing financial interests.

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Wouters, B., Bamber, J., van den Broeke, M. et al. Limits in detecting acceleration of ice sheet mass loss due to climate variability. Nature Geosci 6, 613–616 (2013). https://doi.org/10.1038/ngeo1874

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