Climatic variability in Central Indian Himalaya during the last ∼1800 years: Evidence from a high resolution speleothem record

Abstract

Stable isotopes from a U/Th dated aragonite stalagmite from the Central Kumaun Himalaya provide evidence of variation in climatic conditions in the last ∼1800 years. The δ18O and δ13C values vary from −4.3‰ to −7.6‰ and −3.4‰ to −9.1‰ respectively, although the stalagmite was not grown in isotopic equilibrium with cave drip water, a clear palaeoclimatic signal in stalagmite δ18O values is evident based on the regional climate data. The stalagmite showed a rapid growth rate during 830–910 AD, most likely the lower part of Medieval Warm Period (MWP), and 1600–1640 AD, the middle part of Little Ice Age (LIA). Two distinct phases of reduced precipitation are marked by a 2‰ shift in δ18O values towards the end of MWP (∼1080–1160 AD) and after its termination from ∼1210 to 1440 AD. The LIA (∼1440–1880 AD) is represented by sub-tropical climate similar to modern conditions, whereas the post-LIA was comparatively drier. The Inter Tropical Convergence Zone (ITCZ) was located over the cave location during wetter/warmer conditions. When it shifted southward, precipitation over the study area decreased. A prominent drop in δ18O and δ13C values during the post-LIA period may also have been additionally influenced by anthropogenic activity in the area.