Effect of summer accumulation on glacier mass balance on the Tibetan Plateau revealed by mass-balance model

Abstract

The characteristics and sensitivities of a cold-based glacier on the Tibetan Plateau, where the summer monsoon provides most of the mass input to glaciers, are discussed using an energy-balance model incorporating the process of water refreezing. The model accurately represents the observational results related to the mass balance of Xiao Dongkemadi glacier on the central plateau during 1992/93. Our data revealed that the mass balance of cold glaciers cannot simply be described by the surface mass/heat balances, because about 20% of infiltrated water is refrozen and thus does not run off from the glacier. Model calculations demonstrate that glaciers in an arid environment can maintain their mass since the monsoon provides precipitation during the melting season. Snowfall in summer keeps surface albedo high and largely restrains ablation. Nevertheless, the calculations also make clear that glaciers on the plateau are more vulnerable than those of other regions because of summer accumulation. In the monsoon climate, warming would cause not only a decrease in accumulation, but also a drastic increase in ablation in combination with surface-albedo lowering. Therefore, although glaciers on and around the plateau can be sustained by summer accumulation, they are more vulnerable to warming than winter-accumulation-type glaciers.

Glacier mass variation and its effect on surface runoff in the Beida River catchment during 1957–2013

“…However, the maximum accumulation occurred in June, rather than July or August. Snowfall during the summer could, with warming, fall as rain and the decrease in fresh snow would then reduce the glacier surface albedo, leading to greater ablation (Fujita and Ageta, 2000;Fujita, 2008). Controlled by high temperature, ablation is most intense in July and August, with an average monthly ablation of 226.4 mm w.e..…”

Reconstruction of the mass balance of Muztag Ata No. 15 glacier, eastern Pamir, and its climatic drivers

“…This indicates that MZ15 glacier is a spring-summer accumulation-type glacier, according to the classification of glaciers on the TP proposed by Maussion and others (2013). This is different from spring accumulation-type glaciers with most accumulation occurring in spring (Yang and others, 2013) and summer accumulation-type glaciers with most accumulation occurring in summer (Fujita and Ageta, 2000). The snowfall in the ablation season was 1452 mm w.e.…”

“…Compared with Parlung No. 94 glacier in the southeast TP, Zhadang glacier in the south TP and Xiao Dongkemadi glacier in the central TP (Fujita and Ageta, 2000;Yang and others, 2013;Zhu and others, 2017b), MZ15 glacier showed relatively low melt and accumulation but high sublimation at an annual timescale. In addition, this glacier shows characteristics of spring-summer accumulation with most snowfall occurring in the ablation season or summer.…”

“…H sen and H lat are the sensible and latent heat fluxes calculated using the bulk method (Fujita and Ageta, 2000). Subsurface heat flux (QG) and C en are estimated following Fujita and Ageta (2000). For detailed model information and parameters, refer to Table A1 and Appendix C. The primary data involved with the application of the above stated model include daily air temperature, relative humidity, wind speed and incoming shortwave radiation from AWS2, as well as precipitation from AWS1.…”

“…Outgoing longwave radiation (L out ) is computed from the surface temperature using the Stefan-Boltzmann law. H sen and H lat are the sensible and latent heat fluxes calculated using the bulk method (Fujita and Ageta, 2000). Subsurface heat flux (QG) and C en are estimated following Fujita and Ageta (2000).…”