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Antarctic iceberg impacts on future Southern Hemisphere climate

Abstract

Future iceberg and meltwater discharge from the Antarctic ice sheet (AIS) could substantially exceed present levels, with strong implications for future climate and sea levels. Recent climate model simulations on the impact of a rapid disintegration of the AIS on climate have applied idealized freshwater forcing scenarios1,2 rather than the more realistic iceberg forcing. Here we use a coupled climate–iceberg model to determine the climatic effects of combined iceberg latent heat of fusion and freshwater forcing. The iceberg forcing is derived from an ensemble of future simulations conducted using the Penn State ice-sheet model3. In agreement with previous studies, the simulated AIS meltwater forcing causes a substantial delay in greenhouse warming in the Southern Hemisphere and activates a transient positive feedback between surface freshening, subsurface warming and ice-sheet/shelf melting, which can last for about 100 years and may contribute to an accelerated ice loss around Antarctica. However, accounting further for the oceanic heat loss due to iceberg melting considerably increases the surface cooling effect and reduces the subsurface temperature feedback amplitude. Our findings document the importance of considering realistic climate–ice sheet–iceberg coupling for future climate and sea-level projections.

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Fig. 1: Meltwater forcing scenarios and associated AIS sea-level contribution.
Fig. 2: Uncertainty of global and Southern Hemisphere temperature trajectories related to AIS meltwater discharge.
Fig. 3: Impact of MWF on SAT.
Fig. 4: Impact of icebergs on SAT and subsurface ocean temperatures.
Fig. 5: Impact of iceberg processes on ice–ocean feedback.

Data availability

The data that support the findings of this study are available from the corresponding author on request.

Code availability

The numerical model codes that support the findings of this study are available from the corresponding author on request.

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Acknowledgements

This research was supported by the National Science Foundation under award No. 1341394. A.T. is supported by the Institute for Basic Science, South Korea (Grant No. IBS-R028-D1).

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F.S., A.T. and T.F designed the study. F.S conducted the model simulations and performed the analysis. F.S. and A.T. wrote the manuscript. T.F, R.D. and D.P. contributed to the writing of the manuscript. All authors contributed to interpreting the results and made substantial improvements to the manuscript.

Corresponding author

Correspondence to Axel Timmermann.

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The authors declare no competing interests.

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Peer review information: Nature Climate Change thanks Nicolas Jourdain and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Table 1 and Figs. 1–6.

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Schloesser, F., Friedrich, T., Timmermann, A. et al. Antarctic iceberg impacts on future Southern Hemisphere climate. Nat. Clim. Chang. 9, 672–677 (2019). https://doi.org/10.1038/s41558-019-0546-1

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