Uncertainty quantification of the multi-centennial response of the Antarctic ice sheet to climate change

• Main Authors: Bulthuis, Kevin, Arnst, Maarten, Sun, Sainan, Pattyn, Frank
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: Glaciologie; Antarctic; Misi; The Antarctic; Antarc*; Ice Sheet; Ice Shelf; The Cryosphere
• Online Access: http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/298453; https://dipot.ulb.ac.be/dspace/bitstream/2013/298453/1/doi_282097.pdf

Abstract. Ice loss from the Antarctic ice sheet (AIS) is expected to becomethe major contributor to sea level in the next centuries. Projections of theAIS response to climate change based on numerical ice-sheet models remainchallenging due to the complexity of physical processes involved in ice-sheetdynamics, including instability mechanisms that can destabilise marine basinswith retrograde slopes. Moreover, uncertainties in ice-sheet models limit theability to provide accurate sea-level rise projections. Here, we applyprobabilistic methods to a hybrid ice-sheet model to investigate theinfluence of several sources of uncertainty, namely sources of uncertainty inatmospheric forcing, basal sliding, grounding-line flux parameterisation,calving, sub-shelf melting, ice-shelf rheology and bedrock relaxation, on thecontinental response of the Antarctic ice sheet to climate change over thenext millennium. We provide probabilistic projections of sea-level rise andgrounding-line retreat, and we carry out stochastic sensitivity analysis todetermine the most influential sources of uncertainty. We find that allinvestigated sources of uncertainty, except bedrock relaxation time,contribute to the uncertainty in the projections. We show that thesensitivity of the projections to uncertainties increases and thecontribution of the uncertainty in sub-shelf melting to the uncertainty inthe projections becomes more and more dominant as atmospheric and oceanictemperatures rise, with a contribution to the uncertainty in sea-level riseprojections that goes from 5 % to 25 % in RCP 2.6 to more than 90 % inRCP 8.5. We show that the significance of the AIS contribution to sea levelis controlled by the marine ice-sheet instability (MISI) in marine basins,with the biggest contribution stemming from the more vulnerable WestAntarctic ice sheet. We find that, irrespective of parametric uncertainty,the strongly mitigated RCP 2.6 scenario prevents the collapse of the WestAntarctic ice sheet, that in both the RCP 4.5 and RCP 6.0 scenarios ...