Characterizing 4 decades of accelerated glacial mass loss in the west Nyainqentanglha Range of the Tibetan Plateau

Glacier retreat is altering the water regime of the Tibetan Plateau (TP) as the region's climate changes, but there remain substantial gaps in our knowledge of recent glacier loss in this region due to the difficulty of making direct high-mountain observations, and this limits our ability to predict the future of this important water resource. Here, we assessed 44 years of glacier area and volume changes in the major west Nyainqentanglha Range (WNR) that sup-plies meltwater to the densely populated Lhasa River basin and Nam Co, the second largest endorheic lake on the TP. Between the two periods 1976-2000 and 2000-2020, we found that the glacier areal retreat rate more than doubled (from-0.54 +/- 0.21 % a(-1)to-1.17 +/- 0.30 % a(-1)), and sur -face lowering also accelerated (from -0.26 +/- 0.09 to -0.37 +/- 0.15 m w.e a(-1)) with particularly intense melting after 2014. This acceleration is similar in both timing and magnitude to that observed for Himalayan glaciers farther south. Besides, the areal retreat rate and mass loss rate of most glaciers in the WNR were not synchronized. To understand the sensitivity of WNR glaciers to climate forcing, we examined the effects of topography, debris cover and the presence of proglacial lakes on our observed changes. We found consistently faster areal retreat but slower thinning rates on steeper slopes and an inconsistent relationship with aspect. We concluded that our observed spatial and temporal patterns of glacier change were dominated by observed local variations in temperature and precipitation, the melt-reducing role of supraglacial debris, and the increasing influence of ice-marginal lakes on glacier ablation.

Automated summary

Glacier retreat in the Tibetan Plateau is resulting in changes to its water system as a result of climate change. The lack of direct high-mountain observations has hindered our understanding of recent glacier loss in the region and limits our ability to predict the future of this vital water resource. A study of the west Nyainqentanglha Range revealed that glacier area and volume have been decreasing over the past 44 years, with an acceleration in retreat rate and surface lowering, particularly after 2014.