Reconstructing multi-temporal Glacier area changes to improve mass balance estimates in the Southeastern Tibetan Plateau (2000–2025)

The southeastern Tibetan Plateau (SETP), a critical component of the “Asian Water Tower”, hosts a large concentration of maritime temperate glaciers that are highly sensitive to climate change. However, persistent cloud cover, seasonal snow, and supraglacial debris complicate consistent long-term glacier mapping, while the use of static glacier boundaries may introduce temporal mismatches in altimetry-based glacier mass-change estimates. In this study, we developed a multi-source data-fusion framework on Google Earth Engine (GEE) to reconstruct glacier-area changes in the SETP from 2000 to 2025 at five-year intervals and 30 m spatial resolution. Random Forest classifiers were used to integrate Landsat and Sentinel-2 optical imagery, Sentinel-1 synthetic-aperture-radar data, and NASADEM-derived topographic information, supporting glacier delineation under complex surface and atmospheric conditions. The reconstructed glacier area decreased from 8,083 ± 664 km2 in 2000 to 6,228 ± 572 km2 in 2025, corresponding to a cumulative loss of 22.9 ± 3.6% and a mean loss rate of 80.51 ± 10.51 km2 yr−1. The mean area-loss rates were 51.31 ± 6.51 km2 yr−1 during 2000–2010 and 92.99 ± 15.55 km2 yr−1 during 2010–2025, indicating a higher average loss rate in the later period. By combining satellite-altimetry-derived elevation changes from ICESat, CryoSat-2, and ICESat-2 with the reconstructed time-varying glacier areas, we estimated a mean glacier mass-change rate of −6.51 ± 1.22 Gt yr−1 during 2003–2022. Compared with using a fixed 2003 glacier area, the time-varying-area calculation reduced the estimated mass-loss magnitude by 0.63 Gt yr−1, equivalent to 8.8% of the fixed-area estimate. These results indicate that incorporating time-varying glacier areas can reduce temporal mismatch in altimetry-based mass-change estimation and improve the temporal consistency of regional glacier mass-change assessments.