Late Pleistocene- Holocene Dynamics of a Central Himalayan Glacier using multi-proxy data

Palaeoglacial reconstruction based on geomorphological mapping in the Pindari glacier valley of Central Himalaya has revealed the presence of five glacial stages with decreasing magnitude. The oldest and most extensive stage-I glaciation deposited sediments upto an altitude of 2200 masl. The stage-II glaciations luminescence dated to 25 × 2 ka, has deposits at 3200 masl. Remnants morainic ridges found around 3850 masl and dated to 6 × 1 ka represent the Stage-III glaciations. The sharp crested crescentic moraine extending from around 3650 masl to 3900 masl is attributed to stage-IV glaciation and is dated to 3 × 1 ka. Four sharp crested unconsolidated moraines on the valley floor represent the stage-V. A 435 cm deep Glacio-lacustrine sedimentary deposit from Jeha Gaer, in the vicinity of Pindari Glacier has been analysed using multiproxy data. The palynological and mineral magnetic data aided with 14C and Optically Stimulated Luminescence (OSL) dates suggests that the region has witnessed variability in climatic conditions. The study suggests that this region has experienced at least six major natural climatic changes during the last 7,000 years. The climate for the region has been worked out to be cold and dry during 7 ka BP followed by five different vegetational shifts. The vegetation complex as marked by high conifers associated with broad leaved as well as herbaceous taxa and high magnetic susceptibility suggests the amelioration of climate during 7 ka to 4.9 ka BP. Thereafter, during 4.9 ka to 1.75 ka BP, the climate once again shows cold and drier condition as evidenced by acceleration of alpine herbaceous taxa with gradual decrement of conifers and broad leaved taxa. However, during 1.75 ka to 0.9 ka BP, the climate seems to have become relatively warm and moist (~Medieval Warm Period) as evidenced by the presence of both conifers and broad leaved taxa along with fair amount of Rhododendron. During 0.9 ka to 0.2 ka BP, a drastic climatic change has been witnessed (~Little Ice Age) as evidenced by the relative decline in conifers and broad leaved taxa except Quercus and Rhododendron. The sediments of this zone also show lower values of the magnetic susceptibility. Since the last 300 yr BP onwards, the vegetation complex including conifers, broad leaved taxa along with herbaceous elements along with high magnetic susceptibility indicates warm and moist climatic regime. The presence of cereals (>60μm) along with culture pollen like Tubulifloreae, Acanthaceae, Caryophyllaceae and Polygonaceae also support the high pastoral activity during this phase. Further, the steady presence of both monolete and trilete fern spores suggest an overall warm and moist climatic condition as prevailing presently in and around the study area. It is hereby emphasised that both the palynological and environmental magnetic climatic proxies suggest that in the (central) Himalayan region, the present phase of warming started almost 300 years BP and seems to have been continuing since then. The warming of climate thus seems to have been initiated prior to the beginning of the anthropogenic activity.