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Abstract:
The mid-Pliocene (3.15 to 2.85 million years before present) is the most recent period in Earth’s history when
temperatures and CO2 concentrations were sustainedly higher than pre-industrial values [1], representing an ideal
interval for studying the climate system under conditions similar to those projected for the end of this century.
In these projections, the response of the Antarctic ice sheet (AIS) remains uncertain, including areas generally
considered stable under a warming climate. Therefore, a better understanding of AIS’s behaviour during periods
like the mid-Pliocene will provide valuable information on the potential vulnerability of the composite parts of
the AIS in the future. For this purpose, we have designed numerical experiments of the AIS dynamics during the
mid-Pliocene warm period using the continental-scale ice sheet-shelf model SICOPOLIS [2]. To account for the
uncertainties in the configuration of the AIS and climate conditions prior to this period, we employ a wide range
of initial ice sheet configurations and climatologies, including modern observations, the results from the Pliocene
Model Intercomparison Project (PlioMIP) climate experiments [3], and perturbations to single climatic fields,
allowing us to assess the vulnerability of different AIS sectors to specific forcing mechanisms. Our simulations
show that the West Antarctic ice sheet remains largely ice-free under the chosen range of climate conditions,
except for small portions grounded above sea level. On the contrary, the East Antarctic ice sheet (EAIS) shows
no signs of potential collapse, with an ice loss over a few peripheral sectors largely compensated by an increase
in ice volume over the interior due to increased precipitation rates and surface temperatures remaining well below
the freezing point. Furthermore, our results contrast with existing hypotheses that cast doubt on the stability of the
EAIS during the mid-Pliocene warm period.
References
[1] Cook, C. P., et al. Dynamic behaviour of the East Antarctic ice sheet during Pliocene warmth. Nature Geoscience
6.9 (2013): 765-769.
[2] Sato, T., and Greve, R. Sensitivity experiments for the Antarctic ice sheet with varied sub-ice-shelf melting
rates. Annals of Glaciology 53.60 (2012): 221-228.
[3] Haywood, A. M., et al. Large-scale features of Pliocene climate: results from the Pliocene Model Intercomparison
Project. Clim. Past 9 (2013): 191-209.
