Elmer/Ice used for the interpretation of millennial-scale ice cores drilled at Colle Gnifetti
The high-Alpine ice-core drilling site Colle Gnifetti (CG), Monte Rosa, Swiss/Italian Alps, provides climate records over the last millennium and beyond. However, the full exploitation of the oldest part of the existing ice cores requires complementary knowledge of the intricate glacio-meteorological settings, including glacier dynamics. Here, we present new ice-flow modeling studies of CG, focused on characterizing the flow at two neighboring drill sites in the eastern part of the glacier. The 3-D full Stokes ice-flow model is implemented using the finite element software Elmer/Ice and is thermo-mechanically coupled, includes firn rheology, firn densification and enthalpy transport. Measurements of surface velocities, accumulation, borehole inclination, density and englacial temperatures are used to validate the model output. We calculate backward trajectories using the Runge–Kutta integrator implemented in ParaView and map the core catchment areas. This constrains, for the first time at this site, the so-called upstream effects for the stable water isotope time series of the two ice cores drilled in 2005 and 2013. The model also provides a 3-D age field of the glacier and independent ice-core chronologies for five ice-core sites. Considering the ice core recovered in 2013, the model predicts a near-to-basal age of ~3000 years, which is consistent with radiocarbon dating results. Model results are a valuable addition to the existing glaciological and ice-core datasets. This especially concerns the quantitative estimate of upstream conditions affecting the interpretation of the deep ice-core layers.
Read more: Licciulli C, P. Bohleber, J. Lier, O. Gagliardini, M. Hoelzle and O. Eisen, 2019. A fullStokes ice-flow model to assist the interpretation of millennial-scale ice cores atthe high-Alpine drilling site Colle Gnifetti, Swiss/Italian Alps. Journal of Glaciology 1-14, DOI: 10.1017/jog.2019.82.