Precipitation variability in the Indian Central Himalaya during last ca. 4,000 years inferred from a speleothem record: Impact of Indian Summer Monsoon (ISM) and Westerlies Bahadur Singh Kotlia * , Anoop Kumar Singh, Lalit Mohan Joshi, Bachi Singh Dhaila Centre of Advanced Study in Geology, Kumaun University, Nainital, 263 002, India article info Article history: Keywords: Indian Central Himalaya Stalagmite Late Holocene Oxygen and carbon isotopes Indian Summer Monsoon (ISM) Westerlies abstract We report the first high resolution stalagmite record from Indian Central Himalaya by using a combined oxygen and carbon isotopic study spanning the last 4000 years. In addition to the multi-decadal events, the stalagmite data also provide information on the variability in the intensity of precipitation [Indian Summer Monsoon (ISM) and Westerlies] in north Indian hills during the Late Holocene. The d 18 O values show strong variability between 2.1‰ and 8.9‰. The extremely high variability points to the monsoon from two different sources compared to other similar aged caves which are primarily controlled by one monsoon, such as the East Asian Summer Monsoon (EASM; although ISM has pene- trated into some parts in the areas of EASM in the past) or the Westerlies. Therefore, we suggest that the Westerlies played an important role in the Late Holocene climate of the Indian Himalaya. As the source of the Westerlies is Mediterranean/Atlantic, the North Atlantic Oscillation (NAO) which was responsible for comparatively stronger Westerlies in southern Europe, may have brought higher precipitation to the north Indian hills. The stronger Westerlies may also have resulted in the highest precipitation between 0.5 and 0.25 ka BP (1450e1700 AD; a part of the LIA) in contrast to the weakening of the Indian Summer Monsoon (ISM) in peninsular India. The stalagmite has also recorded the driest period, peaking at ~3.2 ka BP which may be nearly synchronous with the final collapse of the Harappan culture in north- west India. © 2014 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction The annual migration of the ITCZ (Intertropical Convergence Zone) and seasonal development of the monsoon winds are the key components of Indian climatology. In spring, the ITCZ migrates northward across the Indian Ocean and reaches its northernmost position during boreal summer. During the ISM period, a strong low-level monsoonal air flow is generated by a strong pressure gradient between the low-pressure cell over the Tibetan Plateau and a high-pressure cell over southern Indian Ocean. North of the equator, a strong southern-westerly air flow, known as the Somali or Findlater Jet (Findlater, 1996) transports large quantity of mois- ture, that is then released as monsoon precipitation over some parts of the southern Arabia and Indian subcontinent. Subse- quently, the ITCZ jumps across a wide latitudinal range in a very short time and reaches its southernmost position. Therefore, the seasonal migration of the ITCZ strongly influences the onset, duration and termination of the rainy season in the tropics and subtropics and its structure further affects tropical and also extra tropical climate on a variety of time scales (ranging from monthly to millennial). The Holocene climatic records from the tropical sites have revealed substantial changes in mean state hydrology (Congbin and Fletcher, 1988; Lau and Yang, 1997; An et al., 2000; Gasse, 2000; Maslin and Burns, 2000; deMenocal, 2001; Dykoski et al., 2005; Wang et al., 2005; Broccoli et al., 2006; Hu et al., 2008; Wanner et al., 2008; Yan et al., 2011). However, while the ISM core loca- tions are primarily influenced by changes in the amount of pre- cipitation, regions currently situated near the northernmost extension of the ITCZ most likely are also influenced by changes in the seasonality of monsoon precipitation (Fleitmann et al., 2003; Kotlia et al., 2012) due to shifts in the mean latitudinal position of the ITCZ. The ISM in summer and Westerlies (prevailing winds from Europe) in the winter are the two important atmospheric circula- tion patterns found in the Indian Central Himalaya (e.g., Benn and Owen, 1998). When the ISM is weakening, the Westerlies are * Corresponding author. E-mail address: Bahadur.kotlia@gmail.com (B.S. Kotlia). Contents lists available at ScienceDirect Quaternary International journal homepage: www.elsevier.com/locate/quaint http://dx.doi.org/10.1016/j.quaint.2014.10.066 1040-6182/© 2014 Elsevier Ltd and INQUA. All rights reserved. Quaternary International xxx (2014) 1e10 Please cite this article in press as: Kotlia, B.S., et al., Precipitation variability in the Indian Central Himalaya during last ca. 4,000 years inferred from a speleothem record: Impact of Indian Summer Monsoon (ISM) and Westerlies, Quaternary International (2014), http://dx.doi.org/10.1016/ j.quaint.2014.10.066