Increasing frequency of extreme climatic events in southern India during the Late Holocene: Evidence from lake sediments

In this study, we aim to reconstruct southern India's intrinsic environmental changes over the past 1500 years from 3330 to 1830 cal BP by investigating the sedimentation and weathering dynamics in Lake Shantisagara, one of Karnataka's largest lakes. Four distinct climatic phases were delineated based on sedimentological, geochemical, and End Member Modelling Analysis (EMMA) results. Phase 1 (3330-3100 cal BP) is a short-term low rainfall zone characterized by a calm hydrodynamic environment and weak chemical weathering. Phase 2 (3100-2800 cal BP) is a climatically unstable phase, fluctuating between low and high rainfall conditions. Phase 3 (2800-2200 cal BP) is characterized by a stable, low rainfall climate with weak fluvial activity and chemical weathering. It is followed by a highly unstable phase marked by frequent extreme climatic events (Phase 4; 2200-1830 cal BP). Our study reveals a highly unstable hydrodynamic condition that culminated in potentially catastrophic high rainfall events that triggered intense and frequent floods in southern India around ∼2208, 2054, 1958, and 1891 cal BP. Comparative studies of regional records show that the regional climate pattern is similar. There is a strong effect of Total Solar Irradiance (TSI), Sea Surface Temperature (SST) off the Malabar coast, location of the Intertropical Convergence Zone (ITCZ), and the El Niño Southern Oscillation (ENSO) on the monsoon system in southern India. This suggests that there is a global teleconnection.