Glacier mass loss is higher than previous estimates in the Baspa River basin, Himachal Pradesh

Glacier mass balance is an essential parameter in assessing glaciers' health. Numerous methods are currently available to estimate mass balance, including the Improved Accumulation Area Ratio (IAAR). One helpful advantage of the IAAR method is that it can be used to assess future changes in the mass balance. However, the current methodology uses a basin-wise equilibrium line altitude (ELA). It can add errors in the mass balance estimate due to spatial variability in ELA caused by meteorological and terrain parameters. The error can be reduced if ELA is estimated for individual glaciers. The model results were validated using available field-based mass balance data from two glaciers in the basin for the periods 1985–1991, 2001–2003, and 2011–2013. A comparison between the original IAAR and the methods indicates a reduction in mass balance estimation error by 19 ± 6%. The ice loss for 33 glaciers was estimated in the Baspa River basin using the modified IAAR as 0.11 ± 0.4 Gt·a^–1, and by an IAAR method, it was estimated as 0.03 ± 0.6 Gt·a^–1. These results suggest that glaciers in the Baspa basin are losing mass at a higher rate than previous estimates, heralding quick attention to glacier conservation. Furthermore, the root mean square error (RMSE) of the IAAR method (with a single PG) relative to field data was 0.82 m·w·e·a^–1, whereas the modified IAAR (with multiple PGs) reduced the RMSE to 0.2 m·w·e·a^–1, demonstrating a substantial improvement in model performance.