Assessment of interannual and seasonal glacier mass changes in the Karakoram during 2018–2022 using ICESat-2 data

Abstract

Glaciers are key indicators of climate change and are crucial for maintaining the security of the regional water supply. The glacier mass change (GMC) of Karakoram from October 2018 to September 2022 is estimated at regional and grid-cell scales using the ICESat-2/ATL06 altimetry data and the GMC series is decomposed with the Seasonal-Trend Decomposition Procedure Based on Loess (STL) method. Then the interannual and seasonal variations in GMC and their links with meteorological changes are analyzed. The results indicate that: (1) The main period of glacier mass accumulation over the year in the Karakoram is April – June (AMJ), primarily in eastern Karakoram (EK) and central Karakoram (CK), followed by January - March (JFM), primarily in the western Karakoram (WK) and CK. The main period of glacier melting in the Karakoram is July - September (JAS) followed by October - December (OND), and glaciers in the southern side of Karakoram (SK) lost more masses than those in the northern side of Karakoram (NK). (2) The seasonal variability of glacier mass change is region-dependent with SK glaciers has more variability than NK glaciers, and elevation-dependent with the magnitude of variation up to 6 m w.e. below 4000 m a.s.l. while less than 3 m w.e above 4000 m a.s.l.. (3) The rate of glacier mass losses in the Karakoram increased from the west to the east along longitude (i.e., −0.23 ± 0.12 m w.e.a-1 in WK, −0.22 ± 0.11 m w.e.a-1 in CK, −0.31 ± 0.10 m w.e.a-1 in EK) during 2018–2022, while there is little difference in the annual change rate of glacier mass loss in the SK and the NK. (4) The trend of annual glacier mass variation is spatially consistent with trends of precipitation in JFM and AMJ and air temperature in AMJ and JAS. The 'Karakoram Anomaly' ended due to not only the warming in AMJ and JAS, but also the decrease in precipitation in JFM and AMJ, with the temperature playing a dominant role overall.