Climate models project increases in Antarctic surface mass balance — the difference between snowfall and evaporative ice loss — due to anthropogenic warming. Observations, however, do not reveal any significant change in mass balance in recent decades. Rates of Antarctic ice loss, or gain, have potentially important implications for both changes in sea level and its predictability.
Michael Previdi and Lorenzo Polvani from Columbia University, USA, investigate the cause of this discrepancy using an ensemble of 35 coupled atmosphere–ocean models. These effectively capture the climatological features of Antarctica's surface mass balance. Comparisons of pre-industrial and future simulations are used to distinguish forced anthropogenic signatures from natural variability.
Results indicate that the large range of natural variability in surface mass balance masks anthropogenic impacts, making them undetectable at present. This explains the apparent inconsistency between observational records and model simulations. Nevertheless, the authors expect that anthropogenic signals will emerge by the 2040s, wherein warmer temperatures and resultant increases in atmospheric moisture content enhance snowfall and thus increase Antarctic surface mass balance, partially mitigating future global sea level rise.
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Simpkins, G. Anthropogenic signals. Nature Clim Change 6, 982 (2016). https://doi.org/10.1038/nclimate3152
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DOI: https://doi.org/10.1038/nclimate3152
