Analysis of surface energy and mass balance in the accumulation zone of Qiyi Glacier, Tibetan Plateau in an ablation season

Abstract

Previous work on glaciers in the Tibetan Plateau has focused mainly on the ablation zone, while only a modest amount of work has been done on surface energy balance in the accumulation zone on glaciers. To better understand glacial melting in the accumulation zone of high-altitude continental glaciers, a physically based energy-balance model was used to investigate characteristics of the surface energy budget and mass balance on Qiyi Glacier, at the northern margin of the Tibetan Plateau, from 30 July to 9 October 2011. The model was validated by comparing the computed and observed mass variation. The result shows that modeled cumulative mass balance was −60.5 mm w.e. and the measured one was −69.6 mm w.e. The modeled and measured accumulated mass balances compared well in August (r = 0.98, p < 0.001), but less so in September due to the influence of precipitation (r = 0.73, p < 0.01). Improved precipitation observation will therefore be needed. In August, the month of greatest melting, net radiation, R n, was the primary component of the SEB, dominating the total surface energy heat fluxes (67 %), followed by turbulent sensible heat flux (13 %), latent heat flux (9 %) and conductive heat flux (11%). However, in September, the contribution of R n sharply decreased (15 %), and sensible heat flux (40 %) was the primary component of the surface energy balance. Over the observation period, R n accounted for only 51 % of the total heat flux. Strong sublimation was found in the accumulation zone during the study summer period, and positive latent heat flux during several days further illustrates that the glacier is occasionally influenced by monsoon activity.