Rapid glacier mass loss in the Southeastern Tibetan Plateau since the year 2000 from satellite observations

Maritime glaciers in the Southeastern Tibetan Plateau (SETP) featuring the largest maritime glaciers in the Tibetan Plateau (TP) have been experiencing dramatic mass loss and interannual variability over the past two decades, increasing risks of glacier avalanches and glacial lake outbursts. However, spatially explicit and high-temporal-resolution glacier mass loss over the entire SETP has not been well quantified. We developed an approach to integrate satellite altimetry (ICESat, CryoSat-2, and ICESat-2) with DEM differencing and satellite gravity to resolve high spatiotemporally resolved glacier surface elevation change and mass balance across the SETP for the past two decades. We generated DEMs from ASTER L1A stereo-images to estimate the multi-year elevation change, which was used to correct for the altimetry-based counterpart. Subsequently, we processed three different satellite altimetry data and total water storage (TWS) products specifically. Finally, we obtained time series of glacier elevation change and mass balance through the integration of satellite altimetry-, satellite gravity-, and DEM-derived elevation changes during 2000–2020. Results show rapid and heterogeneous glacier depletion with a mean mass loss rate of −0.66 ± 0.02 m water equivalent (w.e.)/yr during 2003–2020 and an accelerating trend over the past two decades. The strongest downwasting was observed in the Hengduan Mountains (−1.29 ± 0.32 m w.e./yr). Contiguous glaciers distributed mostly in Bomi County have a slower rate of elevation changes but play a dominant role in the regional mass balance. Glacier terminus types have a significant impact on glacier melting. The mass loss rate of lake-terminating glaciers is 45% higher than that of land-terminating glaciers, suggesting increasing risks of glacial lake outbursts caused by rapid glacier melting across the SETP. These spatially explicit and high-temporal-resolution features of glacier mass loss will be extremely valuable for calibrating and validating glaciological and hydrological models. Our approach also shows a promising application of CryoSat-2 to mountain glaciology and its potential of estimating glacier mass balances over similar regions globally.