Surface mass balance modeling of mountain glaciers in the Caucasus and in the High Mountain Asia

 

            The most significant quantity characterizing current state of a mountain glacier is its surface mass balance (SMB). SMB responds to changing climatic conditions and therefore determines present and future behavior of the glacier. Formulation of SMB in terms of a mathematical model allows better understanding complex processes of the atmospheric impact on glacier dynamics. After several decades of development, common universal modeling principles and approaches have been elaborated. At present, most of the newly developed models are quite similar with only varying details mostly concerning parameterization of heat fluxes.

SMB is an interplay between positive (accumulation) and negative (ablation) components. Ablation is formulated either using temperature-index (positive degree day) approach or surface energy balance calculation (or combination of both). Both these approaches are based on genuine physical principles and that is why they can be easily transformed into computational algorithms. Results of ablation model calculations are relatively easily constrained by observations. In contrast, evaluation of accumulation is much more dependent on poorly constrained factors such as local atmospheric circulation, snow-storm transport (including post-depositional) and avalanche feeding.

Our approach to simulate components of SMB is based on energy balance approach and emulation of meteorological conditions using a simple stochastic weather generator. To validate the model, we use observed SMB data from several mountain glaciers in different environmental conditions – Djankuat (Central Caucasus), Tuyuksu (Zailiyski Alatau), Sary-Tor and Karabatkak (Inner Tien Shan). Suggested approach allows to easily construct an ensemble of numerical experiments and implement Monte Carlo method for the SMB evaluation. This possibility is especially significant for simulation of future states of glaciers according to one or another climatic scenario on a coupled ice flow-SMB model.

The reported study was funded by RFBR, project number 20-05-00681 (“Evolution of glaciation of Inner Tien Shan under climate change and technogenic influence”)