Paleoclimate reconstruction and topographic drivers of piedmont glaciers during the LGM: Insights from the Yarlung Zangbo River source region,Central Himalayas

Abstract

The piedmont glacial landforms on the northern foothills of the Central Himalayas provide critical records of the Last Glacial Maximum (LGM) glaciation, yet the glacier–environment interactions in the Yarlung Zangbo River source region (SYZR) remain poorly constrained. Integrating field surveys, remote sensing, a previously established chronological and glacier reconstruction framework, and a coupled Precipitation-Temperature (P-T) model, this study systematically reconstructs the LGM paleoclimate and investigates its climatic-topographic drivers. Key findings include the following: (1) 20 piedmont glaciers covered 4000 km² during the LGM, 9.6 times of modern extent, with the largest lobes in Jiemayangzong and Kubiqu basins; (2) glacier scales show strong negative correlations with basal elevation (5000–5100 m) and slope (<10°), while resistant leucogranite bedrock preserved high divides by attenuating the “glacial buzzsaw” effect; (3) the P-T modeling reveals an Equilibrium-Line Altitudes (ELA) depression of 357 ± 169 m, a temperature decrease of 1.6 to 4.6°C, and a precipitation reduction of 10% to 28% during the LGM compared to modern levels. Topographic gaps that funneled moisture created significant spatial heterogeneity in glacier morphological characteristics. This study quantitatively resolves the LGM climate sensitivity of Himalayan piedmont glaciers, highlighting synergistic controls of regional climate forcing with local topography, lithology, and moisture availability.