Ice/firn age distribution on the Elbrus Western Plateau (Caucasus) inferred from ice flow model

Abstract

The glaciers of Mount Elbrus (Caucasus) contain paleoclimatic and paleoenvironmental information representative of a vast region. Negligible seasonal melting in the near-summit area of Elbrus ensures excellent preservation of climatic signals. In 2009, a 182.65 m long ice core was obtained from the glacier on the near-summit Western Plateau (WP) of Elbrus. The upper part and basal samples of the core were dated. In this work, a three-dimensional (3D) steady state thermomechanically coupled Stokes flow model for a cold glacier with a rheological law accounting for firn densification, calibrated based on the ice core dating, was applied to model the velocity field and the corresponding distribution of the age of the ice in the central part of the WP. We performed multiple model runs, varying boundary conditions (BCs), ice viscosity, and the inclusion of thermomechanical coupling. The Elmer/Ice software was used for numerical simulation. The model quite accurately reproduces the age of the ice according to ice core data to a depth of 165 m (up to 243 years). Below, the age of the ice increases sharply and the discrepancies in dating between different modeling scenarios become larger. Overall, the simulated ages fell within 68.2 % confidence intervals for the ages of near-bottom ice samples (mean radiocarbon age 1-2 ka). The model is not applicable for dating the lowermost ice layer (3-4 m thick). Future model improvements should focus on accounting for potential melting and identifying areas containing the oldest ice.