On the influence of Greenland outlet glacier bed topography on results from dynamic ice-sheet models

摘要

Prediction of future changes in dynamics of the Earth's ice sheets, mass loss and resultant contribution to sea-level rise are the main objectives of ice-sheet modeling. Mass transfer from icesheet to ocean is, in large part, through outlet glaciers. Subglacial topography plays an important role in ice dynamics; however, trough systems have not been included in bed digital elevation models(DEMS) used in modeling, because their size is close to the model resolution. Using recently collected CReSIS MCoRDs data of subglacial topography and an algorithm that allows topographically andmorphologically correct integration of troughs and trough systems at anymodeling scale (5 kmresolution for SeaRISE), an improved Greenland bed DEM was developed that includes Jakobshavn Isbræ, Helheim,Kangerdlussuaq and Petermann glaciers (JakHelKanPet DEM). Contrasting the different responses of two Greenland ice-sheet models (UMISM and SICOPOLIS) to the more accurately represented bedshows significant differences in modeled surface velocity, basal water production and ice thickness. Consequently, modeled ice volumes for the Greenland ice sheet are significantly smaller using theJakHelKanPet DEM, and volume losses larger. More generally, the study demonstrates the role of spatial modeling of data specifically as input for dynamic ice-sheet models in assessments of future sea-level rise.