Uncertainty in East Antarctic Firn Thickness Constrained Using a Model Ensemble Approach

• Published in: Geophysical Research Letters
• Main Authors: Verjans, V., Leeson, A. A., Mcmillan, M., Stevens, C. M., van Wessem, J. M., van de Berg, W. J., van den Broeke, M. R., Kittel, C., Amory, C., Fettweis, X., Hansen, N., Boberg, F., Mottram, R.
• Other Authors: Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: east Antarctic ice sheet; firn; model ensemble; [SDU]Sciences of the Universe [physics]; Antarctic; East Antarctic Ice Sheet; Antarc*; Ice Sheet
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-03706456; https://hal-insu.archives-ouvertes.fr/insu-03706456/document; https://hal-insu.archives-ouvertes.fr/insu-03706456/file/Geophysical%20Research%20Letters%20-%202021%20-%20Verjans%20-%20Uncertainty%20in%20East%20Antarctic%20Firn%20Thickness%20Constrained%20Using%20a%20Model.pdf; https://doi.org/10.1029/2020GL092060

International audience Mass balance assessments of the East Antarctic ice sheet (EAIS) are highly sensitive to changes in firn thickness, causing substantial disagreement in estimates of its contribution to sea level. To better constrain the uncertainty in recent firn thickness changes, we develop an ensemble of 54 model scenarios of firn evolution between 1992 and 2017. Using statistical emulation of firn densification models, we quantify the impact of firn compaction formulation, differing climatic forcing, and surface snow density on firn thickness evolution. At basin scales, the ensemble uncertainty in firn thickness change ranges between 0.2 and 1.0 cm yr −1 (15%-300% relative uncertainty), with the choice of climate forcing having the largest influence on the spread. Our results show the regions of the ice sheet where unexplained discrepancies exist between observed elevation changes and an extensive set of modeled firn thickness changes estimates, marking an important step toward more accurately constraining ice sheet mass balance.