Priyeshu Srivastava: Multi-proxy record of middle Holocene Indian summer monsoon variability
Channel: Institute for Rock Magnetism
Date: 2021-06-02

12th Institute for Rock Magnetism Conference 

Lightning Talk

Title: Multi-proxy record of middle Holocene Indian summer monsoon variability and its impact on cultural changes in the Indian subcontinent

Authors: Priyeshu Srivastava (1), Varsha Rawat (2) & Suman Rawat (2)

Institutions:
(1) Instituto Oceanográfico, Universidade de São Paulo, Brazil
(2) Wadia Institute of Himalayan Geology, Dehradun, India

Abstract:
The past ~6000 years have been of an important significance in Human history as various prehistoric and historic civilizations have thrived and demised globally in this time interval. Furthermore, this period is also of significance to understand the Human-climate interaction as a causal link between establishment and demise of these civilizations with climate change has been proposed. Therefore, in order to understand the impact of climate variability on cultural changes in the Indian subcontinent, high resolution centennial to millennial scale middle Holocene Indian summer monsoon (ISM) variability was reconstructed from Bednikund lake, located in an alpine meadow of the Pindar basin, Chamoli, Central Himalaya. Environmental magnetic, grain size, and organic geochemical proxies (TOC and δ13Corg) were used to reconstruct the ISM variability. Increased ISM precipitations were found during ~5930-3950 (mid-Holocene climate optimum), ~3380-2830 (Minoan Warm Period), ~2610-1860 (Roman Warm Period), ~1050-760 (Medieval Climate Anomaly), and ~320 cal yr BP to Present (Current Warm Period). The decreased ISM strengths were found during ~3950-3380, ~2830-2610, ~1860-1050 (Dark Ages Cold Period), ~760-580, and ~500-320 cal yr BP (Little Ice Age). The covariance between our records of precipitation change and total solar irradiance for the middle to late Holocene and with Northern hemisphere (NH) temperature for the past two millennia suggested solar insolation as a primary forcing mechanism of ISM variability. The reconstructed paleoclimate combined with archaeology and historical records indicated that ancient Indian civilizations e.g., the Indus Valley (~5200-3300 cal yr BP) and Vedic (~3400-2400 cal yr BP) had established and thrived during periods of strengthened ISM precipitation, whereas their collapse closely corresponded to the decreased strength in ISM. The Indian subcontinent witnessed the rise and fall of various Kingdoms/dynasties between ~2400 and 200 cal yr BP. The agrarian-based economy showed little or no impact of monsoon weakening after ~2400 cal yr BP possibly due to developments and reforms in administrative policies, construction of irrigation systems such as dams, lakes and canals, use of technology for irrigation such as waterwheel, knowledge of double cropping, production of cash crops. The ancient civilizations of India were directly impacted by the strengthening and weakening of ISM, whereas for the later periods, civilizations were able to adapt to climate change.