Statistics Seminar: Quantifying some century-scale uncertainties of the global mean

Dates

Tuesday, April 13, 2021 - 13:00 to 14:00

Speaker:   Andreas Wernecke (Max Planck Institute of Meteorology, Hamburg)

Title:     Quantifying some century-scale uncertainties of the global mean sea level rise contribution from the Antactica's Amundsen Sea

Abstract:

Predictions of the Antarctic ice sheet contribution to sea-level have large uncertainties. Confidence in projections relies on multi-model agreement, probabilistic calibrations to judge simulations with the help of observations and a solid representation of observational uncertainties. 

Each of these factors require statistical considerations which can be challenging and even computationally prohibitive, especially since ice sheet models are often computationally expensive. Here I would like to introduce some of the approaches by which we try to address these challenges. Statistical emulation can be used to investigate diverging results from different ice sheet models. This allows us to highlight the impact of study designs, deepen our understanding of individual processes and give updated probabilistic projections without the need for additional expensive ice sheet model simulations.

Furthermore we adapt a reduced-dimension calibration approach to ice sheets in order to exploit the spatial characteristics of ice thickness change observations. These additional constraints reduce the 50-year sea-level contribution uncertainty interval for the Amundsen Sea sector, West Antarctica, by nearly 40%, compared to a calibration on total mass loss, and by nearly 90% compared to using no observations at all. Lastly, a statistical model of the bedrock topography underneath the ice is built to improve the representation of measurement and interpolation uncertainties on predictive ice sheet simulations. Our most optimistic and pessimistic 100-year projections for Pine Island Glacier, West Antarctica, are 4.7

±0.87 mm and 19.4 ±5.15 mm sea-level equivalent (mean and standard deviation), where the stated uncertainties originate solely from the bedrock. A clear call for caution for the use of any single bedrock topography. Overall, we try to improve our understanding of limitations in modelling the future of the ice sheets and help to substantiate and reduce predictive uncertainties.