Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

An Ice Sheet Model Validation Framework for the Greenland Ice Sheet

TitleAn Ice Sheet Model Validation Framework for the Greenland Ice Sheet
Publication TypeJournal Article
Year of Publication2017
AuthorsAgusti-Panareda, Anna, Diamantakis Michail, Bayona Victor, Klappenbach Friedrich, Butz Andre, Saba Jack, Tezaur Irina, Guerber Jeffrey, Chambers Don P., Evans Katherine J., Kennedy Joseph H., Lenaerts Jan, Lipscomb William H., Perego Mauro, Salinger Andrew G., Tuminaro Raymond S., van den Broeke Michiel R., and Nowicki Sophie M. J.
JournalGeoscientific Model Development
Volume10
Pages1-18
Abstract / Summary

We propose a new ice sheet model validation framework -- the Cryospheric Model Comparison Tool (CmCt) -- that takes advantage of ice sheet altimetry and gravimetry observations collected over the past several decades and is applied here to modeling of the Greenland ice sheet. We use realistic simulations performed with the Community Ice Sheet Model (CISM) along with two idealized, non-dynamic models to demonstrate the framework and its use. Dynamic simulations with CISM are forced from 1991 to 2013 using combinations of reanalysis-based surface mass balance and observations of outlet glacier flux change. We propose and demonstrate qualitative and quantitative metrics for use in evaluating the different model simulations against the observations. We find that the altimetry observations used here are largely ambiguous in terms of their ability to distinguish one simulation from another. Based on basin- and whole-ice-sheet scale metrics, we find that simulations using both idealized conceptual models and dynamic, numerical models provide an equally reasonable representation of the ice sheet surface (mean elevation differences of <1 m). This is likely due to their short period of record, biases inherent to digital elevation models used for model initial conditions, and biases resulting from firn dynamics, which are not explicitly accounted for in the models or observations. On the other hand, we find that the gravimetry observations used here are able to unambiguously distinguish between simulations of varying complexity, and along with the CmCt, can provide a quantitative score for assessing a particular model and/or simulation. The new framework demonstrates that our proposed metrics can distinguish relatively better from relatively worse simulations and that dynamic ice sheet models, when appropriately initialized and forced with the right boundary conditions, demonstrate predictive skill with respect to observed dynamic changes occurring on Greenland over the past few decades. An extensible design will allow for continued use of the CmCt as future altimetry, gravimetry, and other remotely sensed data become available for use in ice sheet model validation.

URLhttps://doi.org/10.5194/gmd-10-1-2017
DOI10.5194/gmd-10-1-2017
Journal: Geoscientific Model Development
Year of Publication: 2017
Volume: 10
Pages: 1-18
Publication Date: 01/2017

We propose a new ice sheet model validation framework -- the Cryospheric Model Comparison Tool (CmCt) -- that takes advantage of ice sheet altimetry and gravimetry observations collected over the past several decades and is applied here to modeling of the Greenland ice sheet. We use realistic simulations performed with the Community Ice Sheet Model (CISM) along with two idealized, non-dynamic models to demonstrate the framework and its use. Dynamic simulations with CISM are forced from 1991 to 2013 using combinations of reanalysis-based surface mass balance and observations of outlet glacier flux change. We propose and demonstrate qualitative and quantitative metrics for use in evaluating the different model simulations against the observations. We find that the altimetry observations used here are largely ambiguous in terms of their ability to distinguish one simulation from another. Based on basin- and whole-ice-sheet scale metrics, we find that simulations using both idealized conceptual models and dynamic, numerical models provide an equally reasonable representation of the ice sheet surface (mean elevation differences of <1 m). This is likely due to their short period of record, biases inherent to digital elevation models used for model initial conditions, and biases resulting from firn dynamics, which are not explicitly accounted for in the models or observations. On the other hand, we find that the gravimetry observations used here are able to unambiguously distinguish between simulations of varying complexity, and along with the CmCt, can provide a quantitative score for assessing a particular model and/or simulation. The new framework demonstrates that our proposed metrics can distinguish relatively better from relatively worse simulations and that dynamic ice sheet models, when appropriately initialized and forced with the right boundary conditions, demonstrate predictive skill with respect to observed dynamic changes occurring on Greenland over the past few decades. An extensible design will allow for continued use of the CmCt as future altimetry, gravimetry, and other remotely sensed data become available for use in ice sheet model validation.

DOI: 10.5194/gmd-10-1-2017
Citation:
Agusti-Panareda, A, M Diamantakis, V Bayona, F Klappenbach, and A Butz.  2017.  "An Ice Sheet Model Validation Framework for the Greenland Ice Sheet."  Geoscientific Model Development 10: 1-18.  https://doi.org/10.5194/gmd-10-1-2017.