Westerly-monsoon variations since the last deglaciation from semi-arid Ladakh region, Trans Himalaya, India

The semi-arid Ladakh region in the Trans Himalaya forms an environmental boundary between North Atlantic and monsoon forcings. Its location in the transient setting of these two climate systems enables to attest slight changes in the dynamics of these components of atmospheric circulation. Variation in climatic conditions from 19.6 to 6.1 ka using multi-proxy investigation (mineral magnetism, stable carbon isotope, palaeoprecipitation, sediment grainsize end member analysis, clay mineralogy and TOC) is studied from Khalsi palaeolake deposit in Ladakh. Considering the inherent uncertainty of radiocarbon chronology, the present study provides millennial to multi-centennial scale resolution of climate variation from the sediment sequence. The results indicate cold arid climate influenced by Westerly circulation for the last 19.6 to 11.1 ka, thereafter from 11.1 to 7.5 ka, monsoon forcings dominated the climate of the region, following the orbitally controlled solar insolation that influenced the position of ITCZ and formed the key driver of the variability of these atmospheric circulations. A short wet phase from-17.4 to 16.5 ka within the dominant Westerly period is attributed to the early wet phase of two-fold H1 event. Westerly regained strength from 7.5 to 6.1 ka during the mid-Holocene coinciding with decreasing insolation, weakening monsoon and enhanced El Nin & SIM;o activities.

Automated summary

Through the investigation of archaeological data from the Ladakh region, it is found that there have been significant changes in climatic conditions from 19.6 to 6.1 thousand years ago, with a transition from westerly circulation to monsoon dominance. This change is closely related to the position of the ITCZ influenced by solar radiation and the variability of atmospheric circulation. The study also suggests the occurrence of an early wet phase of two-fold H1 events during a period of westerly dominance. The mid-Holocene period from 7.5 to 6.1 thousand years ago was characterized by westerly regain, coinciding with decreasing insolation, weakening monsoon, and enhanced El Nin & SIM;o activities.