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Abstract:
Glaciers across the globe have largely been retreating under the impacts of global warming. However, few glaciers of the Karakoram (KR) region of Karakoram-Himalayas (KH) have displayed anomalous stability or even surge, perplexing glaciologists all around the globe. The phenomenon is widely known as the "Karakoram Anomaly," and although many mechanisms and manifestations have been reported, the present study unravels the role of Western Disturbances (WDs) in establishing and sustaining the anomaly. The present study is the first attempt at quantifying the critical impact of synoptic scale systems on a very regional phenomenon. These upper-tropospheric mid-latitude cyclones travel eastward embedded in subtropical westerly Jetstream (STWJ), impacting the region during the boreal winter and dictating the mass-balance variability of the region. The present study applied a tracking algorithm to three global reanalysis datasets for 39 seasons (1980-2019; Nov-Mar). Composite statistics for tracks passing through KR revealed a ~10% increase in the WD-associated precipitation intensity. WDs were found to provide ~65% of the total seasonal snowfall in the region, establishing them as the primary source of accumulation. Moreover, their contribution to snowfall volume over the core glaciated regions of Karakoram has increased by ~27% in recent decades. A simultaneous decline of about ~17% in the precipitation received from non-WD sources was also observed. Results suggest that the enhanced intensity of WDs is a by-product of increased baroclinic instability, the poleward shift of the STWJ mean latitudinal position, and an eastward shift in their core genesis zone.
