21 Dec 2021
21 Dec 2021
Status: this preprint is currently under review for the journal TC.

The Antarctic contribution to 21st century sea-level rise predicted by the UK Earth System Model with an interactive ice sheet

Antony Siahaan1, Robin Smith2, Paul Holland1, Adrian Jenkins1,a, Jonathan M. Gregory2,3, Victoria Lee4, Pierre Mathiot3,b, Tony Payne4, Jeff Ridley3, and Colin Jones5 Antony Siahaan et al.
  • 1British Antarctic Survey, Cambridge, UK
  • 2NCAS/Department of Meteorology, University of Reading, Reading, UK
  • 3Met Office Hadley Centre, Exeter, UK
  • 4CPOM/Bristol Glaciology Centre, University of Bristol, Bristol, UK
  • 5NCAS/University of Leeds, Leeds, UK
  • anow at: University of Northumbria, Northumbria, UK
  • bnow at: CNRS/Université Grenoble Alpes, Grenoble, France

Abstract. The Antarctic Ice Sheet will play a crucial role in the evolution of global mean sea-level as the climate warms. An interactively coupled climate and ice sheet model is needed to understand the impacts of ice—climate feedbacks during this evolution. Here we use a two-way coupling between the U.K. Earth System Model and the BISICLES dynamic ice sheet model to investigate Antarctic ice—climate interactions under two climate change scenarios. We perform ensembles of SSP1-1.9 and SSP5-8.5 scenario simulations to 2100, which we believe are the first such simulations with a climate model with two-way coupling between both atmosphere and ocean models to dynamic models of the Greenland and Antarctic ice sheets. In SSP1-1.9 simulations, ice shelf basal melting and grounded ice mass loss are generally lower than present rates during the entire simulation period. In contrast, the responses to SSP5-8.5 forcing are strong. By the end of 21st century, these simulations feature order-of-magnitude increases in basal melting of the Ross and Filchner-Ronne ice shelves, caused by intrusions of warm ocean water masses. Due to the slow response of ice sheet drawdown, this strong melting does not cause a substantial increase in ice discharge during the simulations. The surface mass balance in SSP5-8.5 simulations shows a pattern of strong decrease on ice shelves, caused by increased melting, and strong increase on grounded ice, caused by increased snowfall. Despite strong surface and basal melting of the ice shelves, increased snowfall dominates the mass budget of the grounded ice, leading to an ensemble-mean Antarctic contribution to global mean sea level of a fall of 22 mm by 2100 in the SSP5-8.5 scenario. We hypothesise that this signal would revert to sea-level rise on longer timescales, caused by the ice sheet dynamic response to ice shelf thinning. These results demonstrate the need for fully coupled ice—climate models in reducing the substantial uncertainty in sea-level rise from the Antarctic Ice Sheet.

Antony Siahaan et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2021-371', Anonymous Referee #1, 25 Jan 2022
    • AC1: 'Reply on RC1', Antony Siahaan, 17 Apr 2022
  • RC2: 'Comment on tc-2021-371', Anonymous Referee #2, 20 Mar 2022
    • AC2: 'Reply on RC2', Antony Siahaan, 17 Apr 2022

Antony Siahaan et al.

Antony Siahaan et al.


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Short summary
UKESM is the first Earth system model to fully include interactions of the atmosphere and ocean with the Antarctic Ice Sheet. Under low greenhouse-gas scenario, the ice sheet remains stable over the 21st century. Under strong greenhouse-gas scenario, the model predicts strong increases in melting of large ice shelves and strong snow accumulation on the surface. The dominance of accumulation leads to a sea level fall at the end of the century.