Observed and modelled ice temperature and velocity along the main flowline of East Rongbuk Glacier, Qomolangma (Mount Everest), Himalaya

Abstract

Knowledge of present-day ice temperature and velocity is important in order to determine how fast a glacier will respond to present and future climate change. We apply a two-dimensional higher-order thermomechanical flowband model to simulate present-day ice temperature and velocity along the main flowline of East Rongbuk Glacier, Qomolangma (Mount Everest), Himalaya. We use recent (2005-11) observational data to validate the numerical model. Modelled and observed ice surface velocities exhibit good agreement. Modelled ice temperatures agree well with observed values in two shallow boreholes that are $ $18 m deep. The model suggests that the ablation zone of East Rongbuk Glacier, km 4 to km 10 from the glacier head, is underlain by temperate ice.

An investigation of the thermomechanical features of Laohugou Glacier No. 12 on Qilian Shan, western China, using a two-dimensional first-order flow-band ice flow model

“…As shown in Fig. 5a and b, the modelled velocities and TIZ sizes increase as λ max increases and m max decreases, similar to the results observed by Flowers et al (2011) and Zhang et al (2013). A large increase in the modelled basal sliding velocity occurs when m max is lower than 0.2.…”

“…However, for the east Rongbuk Glacier on Mt. Everest, which is considered polythermal, Zhang et al (2013) found that the modelled ice temperatures agreed well with the in situ shallow borehole observations when using surface air temperatures as the surface thermal boundary condition. Therefore, careful investigation of the upper thermal boundary condition is highly necessary for glaciers in different regions under different climate conditions.…”

“…5e and 6e). As shown by Zhang et al (2013), our model results are mainly controlled by the shape of the glacial valley, specifically the b index (Sect. 2.1).…”

“…In some studies, T sbc = T air is used (e.g. Zhang et al, 2013), which, as suggested by recent studies, could result in cold bias in ice temperature simulations (Meierbachtol et al, 2015). By contrast, Meierbachtol et al (2015) recommended using the near-surface temperature T dep at a depth where interannual variations of air temperatures are damped (15-20 m deep) as a proxy for the annual mean ice surface temperature.…”

“…In this study, we use the same 2-D, thermomechanically coupled, first-order flow-band ice flow model as Zhang et al (2013). Therefore, we only address a very brief review of the model here.…”