Seasonal and interannual variability of Karakoram glacier surface albedo from AVHRR-MODIS data, 1982–2020

Abstract

The Karakoram glaciers have exhibited anomalous stability amidst global glacier retreat, a phenomenon known as the “Karakoram anomaly”. However, recent observations suggest a potential weakening of this anomaly. Here, we analyze four decades (1982–2020) of AVHRR and MODIS satellite data to quantify glacier surface albedo changes and their linkages to glacier dynamics. Results reveal a significant decline in annual mean albedo across 65 % of the glaciated area, with pronounced reductions in the central Karakoram (−0.004 yr⁻¹) and northern slopes. Seasonal trends show accelerated summer-autumn darkening post-2000, driven by rising temperatures, reduced snowfall, and snow depth variability. Albedo decline correlates strongly with glacier mass loss, particularly at high elevations (>5000 m a.s.l.), where accumulation zones now exhibit accelerated darkening. Surge-type and avalanche-fed glaciers demonstrate slower albedo declines, linked to ice-mass transportation or fresh snow deposition, highlighting their relationship with the glacier anomaly. The primary drivers of albedo changes, including snowfall, air temperature, and radiation flux, with snow depth and temperature contributing most significantly to interannual albedo variability. Black carbon and dust have a minimal effect on albedo changes, only influencing it during the drier months. Since 2000, the ablation season has been extended to ∼127 days, with earlier onset and delayed termination, leading to accelerated thinning and retreat. Mass balance reconstructions indicate a shift from slight positivity (0.06 ± 0.03 m w.e.a⁻¹, 1982–2019) to accelerated loss post-2005, signaling a transition toward regional glacier retreat. These findings underscore the critical role of albedo feedbacks in modulating the Karakoram Anomaly and highlight urgent needs to integrate albedo dynamics into glacio-hydrological models for sustainable water resource management in High Mountain Asia.