Increased snowfall over the Antarctic Ice Sheet mitigated twentieth-century sea-level rise

Abstract

Changes in accumulated snowfall over the Antarctic Ice Sheet have an immediate and time-delayed impact on global mean sea level. The immediate impact is due to the instantaneous change in freshwater storage over the ice sheet, whereas the time-delayed impact acts in opposition through enhanced ice-dynamic flux into the ocean1. Here, we reconstruct 200 years of Antarctic-wide snow accumulation by synthesizing a newly compiled database of ice core records2 using reanalysis-derived spatial coherence patterns. The results reveal that increased snow accumulation mitigated twentieth-century sea-level rise by ~10 mm since 1901, with rates increasing from 1.1 mm decade−1 between 1901 and 2000 to 2.5 mm decade−1 after 1979. Reconstructed accumulation trends are highly variable in both sign and magnitude at the regional scale, and linked to the trend towards a positive Southern Annular Mode since 19573. Because the observed Southern Annular Mode trend is accompanied by a decrease in Antarctic Ice Sheet accumulation, changes in the strength and location of the circumpolar westerlies cannot explain the reconstructed increase, which may instead be related to stratospheric ozone depletion4. However, our results indicate that a warming atmosphere cannot be excluded as a dominant force in the underlying increase.

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Fig. 1: Trends in reconstructed Antarctic-wide snow accumulation and their relationship to the SAM.
Fig. 2: Nineteenth- and twentieth-century relative annual accumulation by Antarctic sector.
Fig. 3: Twentieth-century cumulative mass and sea-level change due to snow accumulation.

Code availability

The code for generating the reconstructions is available from the NASA Goddard Cryosphere data portal (https://neptune.gsfc.nasa.gov/csb/).

Data availability

The snow accumulation reconstructions generated and analysed during this study are available from the NASA Goddard Cryosphere data portal (https://neptune.gsfc.nasa.gov/csb/). The reanalysis data are available as follows: CFSR (https://rda.ucar.edu/pub/cfsr.html), ERA-Interim (https://www.ecmwf.int/en/forecasts/datasets/archive-datasets/reanalysis-datasets/era-interim) and MERRA-2 (https://disc.gsfc.nasa.gov/). The ice core records are hosted at https://ramadda.data.bas.ac.uk/repository/entry/show?entryid=83f2ca40-04b5-4029-a04c-c18b202dc2f8.

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Acknowledgements

We acknowledge everyone involved in the collection and analysis of the ice core records used in our reconstruction, as well as A. Barker and J. Lenaerts for manuscript comments. B.M. and E.R.T. were supported by NASA’s ICESat-2 Project Science Office and the British Antarctic Survey (Natural Environment Research Council), respectively.

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Both authors designed the study. B.M. wrote the manuscript with input from E.R.T. E.R.T. analysed the ice core records. B.M. performed the reconstruction and its analysis thereafter.

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Correspondence to B. Medley.

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Supplementary information

Supplementary Information

Supplementary Methods, Supplementary Figures 1–10, Supplementary Tables 1–5, Supplementary References

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Medley, B., Thomas, E.R. Increased snowfall over the Antarctic Ice Sheet mitigated twentieth-century sea-level rise. Nature Clim Change 9, 34–39 (2019). https://doi.org/10.1038/s41558-018-0356-x

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