TY - JOUR
T1 - Upper bounds on twenty-first-century Antarctic ice loss assessed using a probabilistic framework
AU - Little, Christopher M.
AU - Oppenheimer, Michael
AU - Urban, Nathan M.
N1 - Funding Information:
C.M.L. is grateful for financial support from the Science, Technology and Environmental Policy programme in the Woodrow Wilson School of Public and International Affairs at Princeton University and the Carbon Mitigation Initiative in the Princeton Environmental Institute. The authors thank K. Keller, O. Sergienko and Y. Liu for many helpful suggestions. We also thank A. Shepherd and the Ice Sheet Mass Balance Exercise team for promptly providing data.
PY - 2013/6
Y1 - 2013/6
N2 - Climate adaptation and flood risk assessments have incorporated sea-level rise (SLR) projections developed using semi-empirical methods (SEMs) and expert-informed mass-balance scenarios. These techniques, which do not explicitly model ice dynamics, generate upper bounds on twenty-first century SLR that are up to three times higher than Intergovernmental Panel on Climate Change estimates. However, the physical basis underlying these projections, and their likelihood of occurrence, remain unclear. Here, we develop mass-balance projections for the Antarctic ice sheet within a Bayesian probabilistic framework, integrating numerical model output and updating projections with an observational synthesis. Without abrupt, sustained, changes in ice discharge (collapse), we project a 95th percentile mass loss equivalent to ∼13 cm SLR by 2100, lower than previous upper-bound projections. Substantially higher mass loss requires regional collapse, invoking dynamics that are likely to be inconsistent with the underlying assumptions of SEMs. In this probabilistic framework, the pronounced sensitivity of upper-bound SLR projections to the poorly known likelihood of collapse is lessened with constraints on the persistence and magnitude of subsequent discharge. More realistic, fully probabilistic, estimates of the ice-sheet contribution to SLR may thus be obtained by assimilating additional observations and numerical models.
AB - Climate adaptation and flood risk assessments have incorporated sea-level rise (SLR) projections developed using semi-empirical methods (SEMs) and expert-informed mass-balance scenarios. These techniques, which do not explicitly model ice dynamics, generate upper bounds on twenty-first century SLR that are up to three times higher than Intergovernmental Panel on Climate Change estimates. However, the physical basis underlying these projections, and their likelihood of occurrence, remain unclear. Here, we develop mass-balance projections for the Antarctic ice sheet within a Bayesian probabilistic framework, integrating numerical model output and updating projections with an observational synthesis. Without abrupt, sustained, changes in ice discharge (collapse), we project a 95th percentile mass loss equivalent to ∼13 cm SLR by 2100, lower than previous upper-bound projections. Substantially higher mass loss requires regional collapse, invoking dynamics that are likely to be inconsistent with the underlying assumptions of SEMs. In this probabilistic framework, the pronounced sensitivity of upper-bound SLR projections to the poorly known likelihood of collapse is lessened with constraints on the persistence and magnitude of subsequent discharge. More realistic, fully probabilistic, estimates of the ice-sheet contribution to SLR may thus be obtained by assimilating additional observations and numerical models.
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U2 - 10.1038/nclimate1845
DO - 10.1038/nclimate1845
M3 - Article
AN - SCOPUS:84879743467
SN - 1758-678X
VL - 3
SP - 654
EP - 659
JO - Nature Climate Change
JF - Nature Climate Change
IS - 7
ER -