Uncertainty in East Antarctic firn thickness constrained using a model ensemble approach

Verjans, Vincent and Leeson, Amber and McMillan, Mal and Stevens, Max and van Wessem, Jan Melchior and van de Berg, Willem Jan and van den Broeke, Michiel and Kittel, Christoph and Amory, Charles and Fettweis, Xavier and Hansen, Nicolaj and Boberg, Fredrik and Mottram, Ruth (2021) Uncertainty in East Antarctic firn thickness constrained using a model ensemble approach. Geophysical Research Letters, 48 (7): e2020GL092. ISSN 0094-8276

Abstract

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 1992‐2017. 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 0.2–1.0 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 modelled firn thickness changes estimates, marking an important step towards more accurately constraining ice sheet mass balance.