Assessing Uncertainty in the Dynamical Ice Response to Ocean Warming in the Amundsen Sea Embayment, West Antarctica

Isabel J Nias,Noel Gourmelen,Tamsin L Edwards,Stephen L Cornford,Antony J Payne

doi:10.1029/2019gl084941

Abstract

AbstractIce mass loss from the Amundsen Sea Embayment ice streams in West Antarctica is a major source of uncertainty in projections of future sea level rise. Physically based ice flow models rely on a number of parameters that represent unobservable quantities and processes, and accounting for uncertainty in these parameters can lead to a wide range of dynamic responses. Here we perform a Bayesian calibration of a perturbed parameter ensemble, in which we score each ensemble member on its ability to match the magnitude and broad spatial pattern of present‐day observations of ice sheet surface elevation change. We apply an idealized melt rate forcing to extend the most likely simulations forward to 2200. We find that diverging grounding line response between ensemble members drives an exaggeration in the upper tail of the distribution of sea level rise by 2200, demonstrating that extreme future outcomes cannot be excluded.

Highlights

Despite considerable advances in physically based models of ice dynamics over the last decade (Pattyn et al, 2017), there are still large uncertainties in the projections of future sea level rise from the Antarctic ice sheets
Based ice flow models rely on a number of parameters that represent unobservable quantities and processes, and accounting for uncertainty in these parameters can lead to a wide range of dynamic responses
We perform a Bayesian calibration of a perturbed parameter ensemble, in which we score each ensemble member on its ability to match the magnitude and broad spatial pattern of present-day observations of ice sheet surface elevation change

Summary

Introduction

Despite considerable advances in physically based models of ice dynamics over the last decade (Pattyn et al, 2017), there are still large uncertainties in the projections of future sea level rise from the Antarctic ice sheets. Only in the last few years has the ice sheet modeling community begun to formally consider uncertainty when estimating future contributions to sea level (Applegate et al, 2012; Chang et al, 2014; Edwards et al, 2014a, 2014b, 2019; Gladstone et al, 2012; Levermann et al, 2014; Little et al, 2013; Ritz et al, 2015; Ruckert et al, 2017; Schlegel et al, 2018; Tsai et al, 2017) This delay is due, in part, to computational issues making it difficult to produce sufficiently large ensembles of simulations to investigate parameter uncertainty with available computational resources (Chang et al, 2014)

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