Karakoram temperature and glacial melt driven by regional atmospheric circulation variability

Abstract

Identifying mechanisms driving spatially heterogeneous glacial mass-balance patterns in the Himalaya, including the ‘Karakoram anomaly’, is crucial for understanding regional water resource trajectories. Streamflows dependent on glacial meltwater are strongly positively correlated with Karakoram summer air temperatures, which show recent anomalous cooling. We explain these temperature and streamflow anomalies through a circulation system—the Karakoram vortex—identified using a regional circulation metric that quantifies the relative position and intensity of the westerly jet. Winter temperature responses to this metric are homogeneous across South Asia, but the Karakoram summer response diverges from the rest of the Himalaya. We show that this is due to seasonal contraction of the Karakoram vortex through its interaction with the South Asian monsoon. We conclude that interannual variability in the Karakoram vortex, quantified by our circulation metric, explains the variability in energy-constrained ablation manifested in river flows across the Himalaya, with important implications for Himalayan glaciers’ futures. The mass balance of glaciers will influence regional water resources in the Himalayas. Changes in atmospheric dynamics, the Karakoram vortex contraction, and interaction with the monsoon influence the glacial melt of the region.