Mathematical Modeling of Elbrus Glaciers in the 21st Century: Part 1. Glaciological Model and Setup of Numerical Experiments

This study fills a gap in the long-term assessments of Elbrus glacier parameters, using the GloGEMflow-DD (debris dynamics) model to simulate the glacier evolution. Part 1 provides a detailed description of the model architecture. The model consists of three modules, responsible for calculations of surface mass balance, glacier flow and debris cover transformation. Debris cover expands and thickens as glacier degradation continues. This is important to consider, since a thicker debris layer retards the ice melting. Predictions are based on the data on temperature and precipitation for five SSP climate scenarios from the CMIP6 project. A temperature index method is used to calculate the surface mass balance, taking into account the influence of the debris cover: the ablation of pure ice is adjusted in accordance with the area and thickness of the debris cover. The ice flow module updates the geometry of glaciers and debris cover. The adaptation specific to Elbrus includes the adjustment of the debris cover transformation module, aligning with the geological characteristics of the region. Notably, slope erosion and rockfalls on the glaciers of the volcanic peak can be neglected, with basal debris constituting the main source of surface debris on the glaciers of Elbrus. Hence, the debris-cover source in the model is specified to be the result of bedrock erosion rather than slope erosion. The paper discusses calibration processes that allow using simple modeling methods, such as positive degree-day for surface mass balance, to mimic the real behavior of glaciers. Despite the fact that the validation of the model revealed a slight underestimation of mass loss at the beginning of the 21st century, the general patterns of mass loss are reproduced correctly, although the energy balance has not been explicitly described. Thus, the adjustment of the model ensures its adaptation to the glaciation conditions on Elbrus.