High climate model dependency of Pliocene Antarctic ice-sheet predictions

Aisling M Dolan,Alan M Haywood,Bas De Boer,Daniel J Hill,Jorge Bernales

doi:10.1038/s41467-018-05179-4

Abstract

The mid-Pliocene warm period provides a natural laboratory to investigate the long-term response of the Earth’s ice-sheets and sea level in a warmer-than-present-day world. Proxy data suggest that during the warm Pliocene, portions of the Antarctic ice-sheets, including West Antarctica could have been lost. Ice-sheet modelling forced by Pliocene climate model outputs is an essential way to improve our understanding of ice-sheets during the Pliocene. However, uncertainty exists regarding the degree to which results are model-dependent. Using climatological forcing from an international climate modelling intercomparison project, we demonstrate the high dependency of Antarctic ice-sheet volume predictions on the climate model-based forcing used. In addition, the collapse of the vulnerable marine basins of Antarctica is dependent on the ice-sheet model used. These results demonstrate that great caution is required in order to avoid making unsound statements about the nature of the Pliocene Antarctic ice-sheet based on model results that do not account for structural uncertainty in both the climate and ice sheet models.

Highlights

ResultsOver East Antarctica, none of the climate models produce conditions that allow the ISMs to attain the extent of retreat prescribed in the PRISM3 ice-sheet reconstruction, due to a predominantly positive SMB over the Wilkes and the Aurora SGB driven largely by increased precipitation in these regions
We have considered each GCM individually to assess whether the predicted volumes fall within the range of the mean plus or minus the standard deviation of the other models
In cases where only one or no present-day simulations are within one standard deviation of the mean, it suggests that this particular GCM is producing ice-sheets significantly different from the others and is skewing the ensemble means (Supplementary Table 2 and S3)

Summary

Results

Over East Antarctica, none of the climate models produce conditions that allow the ISMs to attain the extent of retreat prescribed in the PRISM3 ice-sheet reconstruction, due to a predominantly positive SMB over the Wilkes and the Aurora SGB driven largely by increased precipitation in these regions It is useful to test the sensitivity of our mid-Pliocene simulations to the prescribed PRISM3 ice-sheet in the climate models It is not possible for each GCM to repeat their PlioMIP1 experiment with a different AIS boundary condition (e.g. modern), we have analysed whether or not the initial conditions prescribed in the ISM impact upon the predicted result. For the mPWP, we consider sea level contribution for the whole of Antarctica for PlioceneIce-PRISM3 and PlioceneIce-PD relative to Bedmap[2] and as a change from the Initial ice sheet

39. Note that ice-shelves are only simulated by the ANICE and SICOPOLIS ISMs

Discussion

Methods