Possible Causes of Anomalous Glacier Mass Balance in the Western Kunlun Mountains

Under current global warming, most glaciers on the Tibetan Plateau have shown significant mass loss during 2000-2019. However, the average glacier mass balance in the western Kunlun Mountains (WKM) was positive during this period. The causes of these opposing average status and the temporal glacier mass changes over the last several decades in the WKM continue to be the subject of active debate. The long-term mass balance of the Guliya Ice Cap (Guliya) in the WKM during 1970-2019 was reconstructed using an energy and mass balance model and calibrated ERA5 data, which was calibrated and validated by in situ measurements and geodetic mass balances. Guliya showed a positive mean mass balance during 2000-2019 because annual snowfall was larger than low ablation-season meltwater caused by low air temperature (T ( a )). At interannual scales, annual mass balances were equally controlled by ablation-season precipitation and T ( a ) during 1970-2019. From 1970s-1990s to 1990s-2010s, most Tibetan glaciers showed decreased mass balance due to increased ablation season T ( a ), while the WKM glaciers experienced increased mass balance due to increased ablation-season precipitation related to changes in the Silk Road Pattern. However, during 2000-2019, the annual mass balance of Guliya followed a decreasing trend due to increasing ablation-season T ( a ). The positive mass balance of the WKM glaciers will cease under future warming due to annual snowfall decreasing below ablation-season meltwater. These changes will threaten lives and livelihoods in the Tarim Basin, whilst also jeopardizing ice core-derived climate histories from the WKM glaciers.

Automated summary

Under the current global warming, glaciers in most of the Tibetan Plateau have been losing significant mass between 2000 and 2019. However, the glaciers in the western Kunlun Mountains (WKM) have shown positive mass balance during this period. The causes of this opposing trend and the temporal changes in glacier mass balance in the WKM have been actively debated. This study reconstructs the long-term mass balance of the Guliya Ice Cap in the WKM from 1970 to 2019 using an energy and mass balance model and calibrated ERA5 data. The study finds that Guliya had a positive mean mass balance between 2000 and 2019, primarily due to larger annual snowfall compared to low ablation-season meltwater caused by low air temperature. At an interannual scale, both ablation-season precipitation and air temperature equally influenced annual mass balances between 1970 and 2019.