Abstract
Rapid retreat of ice in the Amundsen Sea sector of West Antarctica may cause drastic sea level rise, posing significant risks to populations in low-lying coastal regions. Calibration of computer models representing the behavior of the West Antarctic Ice Sheet is key for informative projections of future sea level rise. However, both the relevant observations and the model output are high-dimensional binary spatial data; existing computer model calibration methods are unable to handle such data. Here we present a novel calibration method for computer models whose output is in the form of binary spatial data. To mitigate the computational and inferential challenges posed by our approach, we apply a generalized principal component based dimension reduction method. To demonstrate the utility of our method, we calibrate the PSU3D-ICE model by comparing the output from a 499-member perturbed-parameter ensemble with observations from the Amundsen Sea sector of the ice sheet. Our methods help rigorously characterize the parameter uncertainty even in the presence of systematic data-model discrepancies and dependence in the errors. Our method also helps inform environmental risk analyses by contributing to improved projections of sea level rise from the ice sheets. Supplementary materials for this article are available online.
Highlights
Mass loss from the polar ice sheets has the potential to make substantial contributions to future sea level rise
To mitigate the considerable computational challenges posed by the high-dimensional latent process, we reduce the dimensionality of the model output and the data using a logistic principal component analysis (Collins et al, 2002; Lee et al, 2010)
We describe how to compute the logistic principal components (PCs) for binary computer model output and formulate an emulation framework based on them, and set up a calibration model that relies on the reduced-dimensional emulator
Summary
Mass loss from the polar ice sheets has the potential to make substantial contributions to future sea level rise. The ice sheets pose substantial risks to people living near present sea level. Recent observations of increased surface air temperatures at high northern latitudes, and warmer ocean waters at high southern latitudes, suggest that some fraction of this ice may melt over the few decades or centuries (Zhang, 2007; Serreze and Barry, 2011). Geologic observations indicate that the ice sheets can make rapid contributions to sea level (e.g., Deschamps et al, 2012). A significant fraction of the world’s population lives near present sea level (Nicholls et al, 2008), and these people will face an increased risk from storm surges as sea level rise progresses. The future behavior of the ice sheets is a key input for risk analyses (e.g., Lempert et al, 2012)
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