Importance of the seasonal temperature and precipitation variation on glacial evolutions during the LGM at monsoonal Himalaya based on Cogarbu valley

Glacier models have played a more and more important role in reconstructing the paleoglacier and paleoclimate, but the detailed analysis based on high spatial and temporal resolution simulations is rare. In this study, we deeply analyzed the paleoglacial evolution on seasonal scale and its relationship with the large-scale circulation shifts during the Last Glacial Maximum (LGM) in Cogarbu valley, a typical monsoon influence region, using the Open Global Glacier Model driven by 12 Global Circulation Models and their average. The paleoglacier reconstructed under the mean climate is closer to the observations, with the glacier length, area, and volume of 19.8 km, 35.7 km², and 6.6 km³, respectively. The reconstructed equilibrium-line altitude is ~5253 m, about 662 m lower than modern. The temperature has a 4.6 °C decreasing with a 16.3% reduction of precipitation. The seasonal temperature decreases about −4.0, −4.6, −4.2, and − 5.5 °C in spring, summer, autumn, and winter, respectively. Detailed analysis on atmospheric circulation shifts indicates that the high correlation of temperature change between TP and North Atlantic Ocean might be caused by their similar response to the global climate change results from the reduction of insolation rather than baroclinic waves. In summer, southward-shifted and narrowed the Intertropical Convergence Zone weakened the Indian Summer Monsoon, decreasing the summer precipitation of −22.4% compared to modern. In winter, the enhancement of the South Branch of Westerlies increased the winter precipitation of 10.0%. Despite more winter precipitation refueled the glacial accumulation, the decreasing of the summer temperature has dominant influence on the annual net surface mass balance via reducing the summer ablation during the LGM.