Abrupt changes in Indian summer monsoon strength during 33,800 to 5500 years B.P.

Abstract

Speleothem proxy records from northeastern (NE) India reflect seasonal changes in Indian summer monsoon strength as well as moisture source and transport paths. We have analyzed a new speleothem record from Mawmluh Cave, Meghalaya, India, in order to better understand these processes. The data show a strong wet phase 33,500–32,500 years B.P. followed by a weak/dry phase from 26,000 to 23,500 years B.P. and a very weak phase from 17,000 to 15,000 years B.P. The record suggests abrupt increase in strength during the Bølling‐Allerød and early Holocene periods and pronounced weakening during the Heinrich and Younger Dryas cold events. We infer that these changes in monsoon strength are driven by changes in temperature gradients which drive changes in winds and moisture transport into northeast India.

Timing and Structure of the 4.2 ka BP Event in the Indian Summer Monsoon Domain from an Annually-Resolved Speleothem Record from Northeast India

“…18 O values of our records are used to refer to strong and weak monsoons, respectively, consistent with a number of previous studies (e.g., Dayem et al, 2010;Breitenbach et al, 2010;Sinha et al, 2011;Cheng et al, 2012;Sinha et al, 2011;Berkelhammer et al, 2012;Breitenbach et al, 2015;Myers et al, 2015, Dutt et al, 2015Cheng 160 et al, 2012;Kathayat et al, 2016;Kathayat et al, 2017).…”

“…The temperature variations in the cave are 140 small (18.0-18.5°C) and close to the mean annual temperature of the area (Breitenbach et al, 2010 and. A 3-year monitoring study in Mawmluh Cave (Breitenbach et al, 2010) (Breitenbach et al, 2010 andBerkelhammer et al, 2012;Myers et al, 2015;Dutt et al, 2015).…”

Climate-driven sediment aggradation and incision since the late Pleistocene in the NW Himalaya, India

“…Climatic changes related to both ISM oscillations and glacialinterglacial cycles are documented in speleothem oxygen-isotope (δ 18 O) records from Dongge cave, China (Dykoski et al, 2005), the Shillong Plateau of NE India (Dutt et al, 2015), and the Hulu and Sanbao caves of southeast China (Wang et al, 2008) (Fig. 5).…”

“…Speleothem oxygen-isotope records from India and China (e.g., Dutt et al, 2015;Dykoski et al, 2005;Wang et al, 2008) record climate fluctuations on 10 3 yr and shorter timescales related to changes in the Indian Summer Monsoon (ISM) intensity that are superimposed on 10 4 yr trends associated with glacialinterglacial cycles. In general, weak monsoon periods are associated with reduced rainfall in the higher sectors of the Himalaya, whereas strong monsoon periods correlate with increased rainfall (Bookhagen et al, 2005;Wang et al, 2008).…”

The Indian summer monsoon climate during the Last Millennium, as simulated by the PMIP3

“…Fleitmann et al, 2007;Fleitmann et al, 2003;Neff et al, 2001), and the Indian sub-continent (e.g. Berkelhammer et al, 2012;Dixit et al, 30 2015;Dixit et al, 2014a;Dixit et al, 2014b;Dixit, 2013;Dutt et al, 2015;Nakamura et al, 2015).…”