Letter

Important role for ocean warming and increased ice-shelf melt in Antarctic sea-ice expansion

  • Nature Geoscience 6, 376–379 (2013)
  • doi:10.1038/ngeo1767
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Abstract

Changes in sea ice significantly modulate climate change because of its high reflective and strong insulating nature. In contrast to Arctic sea ice, sea ice surrounding Antarctica has expanded1, with record extent2 in 2010. This ice expansion has previously been attributed to dynamical atmospheric changes that induce atmospheric cooling3. Here we show that accelerated basal melting of Antarctic ice shelves is likely to have contributed significantly to sea-ice expansion. Specifically, we present observations indicating that melt water from Antarctica’s ice shelves accumulates in a cool and fresh surface layer that shields the surface ocean from the warmer deeper waters that are melting the ice shelves. Simulating these processes in a coupled climate model we find that cool and fresh surface water from ice-shelf melt indeed leads to expanding sea ice in austral autumn and winter. This powerful negative feedback counteracts Southern Hemispheric atmospheric warming. Although changes in atmospheric dynamics most likely govern regional sea-ice trends4, our analyses indicate that the overall sea-ice trend is dominated by increased ice-shelf melt. We suggest that cool sea surface temperatures around Antarctica could offset projected snowfall increases in Antarctica, with implications for estimates of future sea-level rise.

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Acknowledgements

We are grateful to all members of the EC-Earth consortium for their help and support with the development of the EC-Earth climate model, of which the model NEMO is the ocean module.

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Affiliations

  1. Royal Netherlands Meteorological Institute (KNMI), Wilhelminalaan 10, 3732 GK De Bilt, The Netherlands

    • R. Bintanja
    • , G. J. van Oldenborgh
    • , S. S. Drijfhout
    • , B. Wouters
    •  & C. A. Katsman

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Contributions

G.J.v.O., R.B. and S.D. developed the ideas that led to this paper. G.J.v.O. analysed the observational data. B.W. and R.B. conducted the climate model experiments and analyses. R.B. wrote the main paper, with input from all authors, who discussed the results and implications and commented on the manuscript at all stages.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to R. Bintanja.

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