The Role of the Snow Ratio in Mass Balance Change under a Warming Climate for the Dongkemadi Glacier, Tibetan Plateau

Understanding the effects of the snow ratio on glacier mass balance under variable climatic conditions is crucial for predicting how glaciers will respond to climate change, and for forecasting water supplies to surrounding lowland areas. Due to recent climate change, the historical annual snow ratio of the Dongkemadi (DKMD) Glacier showed a significant increasing trend (0.0538% a(-1), p < 0.05), and an abrupt upward change in 1977 due to decreasing precipitation concentration. Snow ratios with fixed precipitation concentration and nonwarming climate scenarios were calculated to isolate the impact of the snow ratio on glacier mass balance. Under nonwarming conditions, the snow ratio showed little variability, ranging from 88.4% to 99.9%. Glacier modeling results comparing five snow ratio scenarios from 1961 to 2009 showed three main features as follows. (i) Glacier mass balance was low and more sensitive to a warming climate for lower snow ratio scenarios. (ii) The difference in mass balance between the scenarios fluctuated, but generally increased with time. Spatially, the ablation area change was larger (0.4 km(2)), and the equilibrium line altitude was higher (5.9 m) in scenarios with lower snow ratios. (iii) The change in net shortwave radiation was the main reason for changes in glacial melt, and the albedo played a key role in controlling the difference of glacier energy balance between snow ratio scenarios. Rain increment only accounted for about 20%-33% of meltwater increment. Overall, this study provides valuable information to evaluate how snow ratios impact the mass balance of glaciers with ongoing climate change.