Abrupt weakening of the Indian summer monsoon at 8.2 kyr BP

An oxygen isotope record of biogenic carbonate from paleolake Riwasa in northwestern (NW) India provides a history of the Indian Summer Monsoon (ISM) from similar to 11 to 6 kyr B.P. The lake was dry throughout the Late Glacial period when aeolian sands were deposited. Lacustrine sedimentation commenced in the early Holocene and the lake deepened significantly at similar to 9.4 kyr B.P., indicating a strengthening of the ISM in response to summer insolation forcing. This high lake stand was interrupted by an abrupt desiccation, which is marked by a 12-cm limestone hardground that formed during a period of sub-aerial exposure after similar to 8.3 kyr B.P. The base of the hardground surface coincides with the beginning of the '8.2-kyr B.P. cooling event' in the North Atlantic that has been associated with a glacial outburst flood and slowdown of Atlantic meridional overturning circulation. The hardground provides robust evidence of a weakening of the ISM on the Indian subcontinent at similar to 8.2 kyr B.P., and supports previous results of a strong teleconnection between monsoon Asia and North Atlantic climate. Lacustrine sedimentation resumed at similar to 7.9 kyr B.P. suggesting the 8.2-kyr desiccation of paleolake Riwasa represented an abrupt response of the ISM to forcing from the North Atlantic. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).