Role of Different Moisture Sources in Driving the Western Himalayan Past-glacier Advances

Abstract

The fragmented pattern and the rapidly declining preservation of older glacial features/evidences limits the precision, with which glacial chronologies can be established. The challenge is exacerbated by the scarcity of datable material and limitations of dating methods. Nevertheless, the preserved glacial landforms have been fairly utilized to establish glacial chronologies from different sectors of the Indian Himalayas. The existing Himalayan glacial chrono-stratigraphies have revealed that in a single valley, past glacial advances rarely surpass four stages. Thus, local and regional glacial chronologies must be synthesized to understand glacial dynamics and potential forcing factors. This research presents an overview of glacier responses to climate variations revealed by glacial chrono-stratigraphies in the western Indian Himalayan region over the Quaternary (late). The synthesis demonstrated that, although the glacial advances were sporadic, glaciers in western Himalayas generally advanced during the Marine isotope stage (MIS)-3/4, MIS-2, late glacial, Younger Dryas (YD) and Holocene periods. The Holocene has witnessed multiple glacial advances and the scatter is significant. While previous glacial research revealed that Himalayan glaciers were out of phase with the global last glacial maximum (gLGM), weak Indian Summer Monsoon (ISM) has been implicated (ISM was reduced by roughly 20%). Recent research, however, has shown that gLGM glaciation responded to the global cooling associated with the enhanced mid-latitude westerlies (MLW). Further, the magnitude of gLGM glacier advance varied along and across the Himalayas particularly the transitional valleys located between the ISM and MLW influence. It is also evident that both the ISM and MLW have governed the late Quaternary glacial advances in the western Himalayan region. However, the responses of glaciers to ISM changes are more prominent. The insights gained from this synthesis will help us understand the dynamics of glacier response to climate change, which will be valuable for future climate modelling.