Abstract ID: 3.10662 | Accepted as Talk | Talk/Oral | TBA | TBA

Glaciers play a crucial role in the water resources of Central Asia, especially in arid climates where summer rainfall is minimal or absent. This study focuses on the Upper Naryn River basin, covering the catchments of the Big and Small Naryn Rivers, which provide critical water to the Syr Darya River. The catchment contributes the largest glacierized areas, totaling 759 km², including 473 km² in the Big Naryn sub-region and 286 km² in the Small Naryn. Annual monitoring and mass balance analysis are conducted on the Batysh Sook and No. 354 glaciers in the Upper Naryn. We use a distributed glacier mass balance model to calculate the topographically distributed accumulation from a daily meteorological time series and the gridded melt according to an enhanced temperature index approach. This model extrapolates point measurements from 2011 to 2024 and reconstructs mass balance data back to 2003, providing insights into the glacier dynamics of the entire basin. The analysis reveals a consistent mass loss from 2011 to 2024, with a particularly steep decline in the last 2-3 years. From 2011 to 2024, the average annual mass balance was -0.59 m w.e. yr-1 for Batysh Sook and -0.65 m w.e. yr-1 for No. 354. We compared the simulated glacier melt to the measured runoff from discharge gauging stations within Big and Small Naryn as well as to discharge measurements at the glacier terminus at the two monitoring sites. The simulated glacier melt significantly contributes to the river’s runoff, with approximately 7% in June, 36-40% in July-August, and 15% in September. Satellite imagery, including data from Sentinel 2, KH-9, and Landsat, shows that from 1977 to 2021, glaciers in the Big Naryn basin shrank by 157 km² (25%) and in the Small Naryn by 87 km² (23%), with average annual reductions of 3.56 km² and 1.97 km², respectively. Our findings indicate ongoing glacier shrinkage and advance the understanding of regional water resources and climate change impacts, calling for continued monitoring to ensure water availability and improved mitigation.