title: Assessing the Impact of Retreat Mechanisms in a Simple Antarctic Ice Sheet Model Using Bayesian Calibration.
abstract: The response of the Antarctic ice sheet (AIS) to changing climate forcings is an important driver of sea-level changes. Anthropogenic climate change may drive a sizeable AIS tipping point response with subsequent increases in coastal flooding risks. Many studies analyzing flood risks use simple models to project the future responses of AIS and its sea-level contributions. These analyses have provided important new insights, but they are often silent on the effects of potentially important processes such as Marine Ice Sheet Instability (MISI) or Marine Ice Cliff Instability (MICI). These approximations can be well justified and result in more parsimonious and transparent model structures. This raises the question of how this approximation impacts hindcasts and projections. Here, we calibrate a previously published and relatively simple AIS model, which neglects the effects of MICI and regional characteristics, using a combination of observational constraints and a Bayesian inversion method. Specifically, we approximate the effects of missing MICI by comparing our results to those from expert assessments with more realistic models and quantify the bias during the last interglacial when MICI may have been triggered. Our results suggest that the model can approximate the process of MISI and reproduce the projected median melt from some previous expert assessments in the year 2100. Yet, our mean hindcast is roughly 3/4 of the observed data during the last interglacial period and our mean projection is roughly 1/6 and 1/10 of the mean from a model accounting for MICI in the year 2100. These results suggest that missing MICI and/or regional characteristics can lead to a low-bias during warming period AIS melting and hence a potential low-bias in projected sea levels and flood risks.
authors.affiliation: Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors.forename: Kelsey L
authors.identifier: http://orcid.org/0000-0001-9513-2636
authors.initials: KL
authors.lastname: Ruckert
authors.affiliation: GAIA Antarctica, University of Magallanes, Punta Arenas, Chile.|Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Gary
authors.initials: G
authors.lastname: Shaffer
authors.affiliation: Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors.forename: David
authors.initials: D
authors.lastname: Pollard
authors.affiliation: Department of Statistics, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors.forename: Yawen
authors.initials: Y
authors.lastname: Guan
authors.affiliation: Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors.forename: Tony E
authors.initials: TE
authors.lastname: Wong
authors.affiliation: Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, Pennsylvania, United States of America.|Department of Meteorology, The Pennsylvania State University, University Park, Pennsylvania, United States of America.|Department of Geosciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors.forename: Chris E
authors.initials: CE
authors.lastname: Forest
authors.affiliation: Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, Pennsylvania, United States of America.|Department of Geosciences, The Pennsylvania State University, University Park, Pennsylvania, United States of America.|Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Klaus
authors.initials: K
authors.lastname: Keller
mesh_terms: D000864:Antarctic Regions; D001499:Bayes Theorem; D057231:Climate Change; D046448:Ice Cover; D008962:Models, Theoretical