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

Journal name:
Nature Geoscience
Volume:
6,
Pages:
613–616
Year published:
DOI:
doi:10.1038/ngeo1874
Received
Accepted
Published online

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 43cm 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 ±10Gtyr−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.

At a glance

Figures

  1. Recent mass changes of the Greenland and Antarctic ice sheets.
    Figure 1: Recent mass changes of the Greenland and Antarctic ice sheets.

    a, Mass anomalies observed by GRACE (January 2003–September 2012) for Greenland (red) and Antarctica (blue; arbitrarily vertically shifted for clarity). b, RACMO2 SMB, illustrating interannual variability (note the different scale for Antarctica). c, Estimated trend in the GRACE time series as function of record length since the start of the observations. For example, at x=6, trends in the six-year window for January 2003–December 2008 are shown for Greenland (red) and Antarctica (blue). d, As in c, but for accelerations; for explanation on error bars (95% range), see Supplementary Information. SMB, surface mass balance.

  2. Trend and acceleration uncertainty for Greenland.
    Figure 2: Trend and acceleration uncertainty for Greenland.

    a, Uncertainty (95% range, blue area) in mass trend estimates due to stochastic ice sheet variability in SMB and ice discharge as function of observation length for the GrIS. Trends reported here and in a selected number of recent studies are shown as well. b, As in a, but for the accelerations. SLR, sea-level rise.

  3. Trend and acceleration uncertainty for Antarctica.
    Figure 3: Trend and acceleration uncertainty for Antarctica.

    a, Uncertainty (95% range, blue area) in mass trend estimates due to stochastic ice sheet variability as function of observation length for the AIS. These uncertainties are based on the contribution of SMB only. Trends reported here and in a selected number of recent studies are shown as well. b, As in a, but for the accelerations.

References

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Author information

Affiliations

  1. Bristol Glaciology Centre, School of Geographical Science, Bristol BS8 1SS, UK

    • B. Wouters &
    • J. L. Bamber
  2. Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309, USA

    • B. Wouters
  3. Institute for Marine and Atmospheric Research, Utrecht University, 3508 TA Utrecht, The Netherlands

    • M. R. van den Broeke &
    • J. T. M. Lenaerts
  4. Deutsches GeoForschungsZentrum GFZ, 14473 Potsdam, Germany

    • I. Sasgen

Contributions

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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The authors declare no competing financial interests.

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