Continuous Estimates of Glacier Mass Balance in High Mountain Asia Based on ICESat-1,2 and GRACE/GRACE Follow-On Data

Glacier melt in High Mountain Asia (HMA) is an indicator of climate change and has a major impact on the regional hydrology and freshwater supply. We determined the recent status of HMA glaciers based on the first analysis of Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) data. We used the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (FO) data to complement ICESat-1,2 data and validate them independently. We find a good agreement between ICESat-1,2 and GRACE/GRACE-FO data, which demonstrates the high reliability of results. Based on our results, the continuous glacier mass change from 2003 to 2019 is -28 6 Gt yr(-1), which is more negative than stereo imagery-based studies. The regional variability of the glaciers ranges from -1.07 0.10 m yr(-1) in southeastern Nyaingentanglha to +0.16 0.10 m yr(-1) in West Kunlun. ICESat-2 data enable new insight into the continuous measurement of HMA glacier elevation change. Plain Language Summary High Mountain Asia (HMA) is the largest ice-covered region outside the polar regions. Glaciers have been melting for the past decades due to global warming and will probably continue in the coming decades. This threatens the water availability in downstream basins and affects the regional or global climate. Thus, it is important to continuously monitor the states of the glaciers. In this study, the first analysis of data released after the launch of the second generation of the Ice, Cloud, and Land Elevation Satellite (ICESat-2) is provided. The data were used to survey the glacier thickness and mass change in HMA. We used independent gravity satellite data to fill the gap of ICESat, and the two independent data sets agree with respect to the continuous glacier mass change, which indicates the high reliability of the results. We estimate a total mass change of HMA glaciers is -28 6 Gt yr(-1) (Gt = 109 t water) or -0.34 +/- 0.07 m yr(-1) from 2003 to 2019. The spatial variability of the glacier elevation change rates indicates rapid thinning in Nyaingentanglha, but a slight increase in West Kunlun. Key Points . We provide the first look of ICESat-2 data on glacier thickness and mass changes in High Mountain Asia We use independent data from satellite gravimetry to fill data gap of ICESat and obtain nearly continuous glacier mass changes There is a quantitative agreement between satellite gravimetry and satellite altimetry, which show high reliability of result and data

Automated summary

The study analyzed glacier mass changes in High Mountain Asia using ICESat-2 data and satellite gravimetry, finding a consistent and reliable result. From 2003 to 2019, the glaciers in the region experienced negative mass changes, with regional variability.